Введение
Рыба с плавниками Автоматическая таксобокс
| name = Стержон
| image = Acipenser oxyrhynchus (редактировать).png
| image caption = Атлантический стержон (Acipenser oxyrinchus oxyrinchus)
| fossil range =
| taxon = Acipenseridae
| authority = Bonaparte, 1831
| subdivision ranks = Роды
| subdivision =
†Boreiosturion
†Protoscaphirhynchus
†Engdahlichthys
†Anchiacipenser
†Priscosturion
Acipenser (парафилетический)
Huso
Scaphirhynchus
Pseudoscaphirhynchus
Ray finned fish
Automatic taxobox
| name = Sturgeon
| image = Acipenser oxyrhynchus (edit). png
| image caption = Atlantic sturgeon(Acipenser oxyrinchus oxyrinchus)
| fossil range =
| taxon = Acipenseridae
| authority = Bonaparte, 1831
| subdivision ranks = Genera
| subdivision =
†Boreiosturion
†Protoscaphirhynchus
†Engdahlichthys
†Anchiacipenser
†Priscosturion
Acipenser (paraphyletic)
Huso
ScaphirhynchusPseudoscaphirhynchus
Sturgeon (from Old English styrġa ultimately from Proto Indo European *str̥(Hx)yón ) is the common name for the 28 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early Jurassic period, some 174 to 201 million years ago. They are one of two living families of the Acipenseriformes alongside paddlefish (Polyodontidae). The family is grouped into four genera: Acipenser (which is paraphyletic, containing many distantly related sturgeon species), Huso, Scaphirhynchus, and Pseudoscaphirhynchus. Two species (A. naccarii and A. dabryanus) may be extinct in the wild, and one (P. fedtschenkoi) may be entirely extinct. Sturgeons are native to subtropical, temperate and sub Arctic rivers, lakes and coastlines of Eurasia and North America. A Maastrichtian age fossil found in Morocco shows that they also once lived in Africa. Sturgeons are long lived, late maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle like body that is smooth skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging in length. The largest sturgeon on record was a beluga female captured in the Volga Delta in 1827, measuring long and weighing Most sturgeons are anadromous bottom feeders, migrating upstream to spawn but spending most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. Several species of sturgeon are harvested for their roe, which is processed into the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction. Evolution
Fossil history
Acipenseriform fishes appeared in the fossil record some 174 to 201 million years ago, during the Early Jurassic, making them some of the earliest extant actinopterygian fishes. True sturgeons appear in the fossil record during the Upper Cretaceous, with amongst the oldest known remains being a partial skull from the Cenomanian (100–94 million years ago) of Alberta, Canada. In that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils. This is explained in part by the long generation interval, tolerance for wide ranges of temperature and salinity, lack of predators due to size and bony plated armor, or scutes, and the abundance of prey items in the benthic environment. They do, however, still share several primitive characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements, and unique jaw suspension. Phylogeny and taxonomy
Despite the existence of a fossil record, full classification and phylogeny of the sturgeon species has been difficult to determine, in part due to the high individual and ontogenic variation, including geographical clines in certain features, such as rostrum shape, number of scutes, and body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. While ray finned fishes (Actinopterygii) have a long evolutionary history culminating in the most familiar fishes, past adaptive evolutionary radiations have left only a few survivors, such as sturgeons and gars. The wide range of the acipenserids and their endangered status have made collection of systematic materials difficult. The factors have led researchers in the past to identify over 40 additional species that were rejected by later scientists. Whether the species in the Acipenser and Huso genera are monophyletic (descended from one ancestor) or paraphyletic (descended from many ancestors) is still unclear, though the morphologically motivated division between these two genera clearly is not supported by the genetic evidence. An effort is ongoing to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques. The phylogeny of Acipenseridae, as in the cladogram, shows that they evolved from the bony fishes. Approximate dates are from Near et al., 2012. However, multiple recent studies have recovered this arrangement as paraphyletic, instead finding A. oxyrhinchus and A. sturio to form the most basal clade among sturgeons, and all other species being in a separate clade, with the various other species of Acipenser, Scaphirhynchus, Pseudoscaphirhynchus, and Huso to have varying levels of relationship with one another. A potential taxonomy of Acipenseridae is shown here, based on Luo et al. 2019, Nedoluzhko et al. 2020, and Shen et al. 2020. Note the paraphyletic relationships among genera:
The exact placement of Scaphirhynchus varies depending on the study and the methods used, with some placing it within the second most basal clade comprising primarily Pacific species (shown above), whereas others place it in its own clade that is more derived than the secondmost basal clade but less derived than the most derived Atlantic and Central Asian clade. No studies have yet delineated a relationship between it and Pseudoscaphirhynchus. In addition, the exact relationships of the members of the most derived, primarily Atlantic clade vary, although most analyses at least find all the species in it to form a monophyletic clade. The placement of A. sinensis also varies by the study, with some placing it as the only Pacific member of the otherwise Atlantic based most derived clade, whereas others place it with the rest of the Pacific sturgeons as a sister to A. dabryanus. in the rivers that flow into the Black, Azov, and Caspian Seas (Danube, Dnepr, Volga, Ural and Don); the north flowing rivers of Russia that feed the Arctic Ocean (Ob, Yenisei, Lena, Kolyma); in the rivers of Central Asia (Amu Darya and Syr Darya) and Lake Baikal. In the Pacific Ocean, they are found in the Amur River along the Russian Chinese border, on Sakhalin Island, and some rivers in northeast China. Most species are at least partially anadromous, spawning in fresh water and feeding in nutrient rich, brackish waters of estuaries or undergoing significant migrations along coastlines. However, some species have evolved purely freshwater existences, such as the lake sturgeon (Acipenser fulvescens) and the Baikal sturgeon (A. baerii baicalensis), or have been forced into them by human or natural impoundment of their native rivers, as in the case of some subpopulations of white sturgeon (A. transmontanus) in the Columbia River and Siberian sturgeon (A. baerii) in the Ob basin. Physical characteristics
Sturgeons retain several primitive characteristics from the bony fishes. Along with other members of the subclass Chondrostei, they are unique among bony fishes because their skeletons are almost entirely cartilaginous. To maintain structure, sturgeons are one of few organisms to retain a post embryonic notochord that acts like a soft spine running through the body. Notably, however, the cartilagineous skeleton is not a primitive character, but a derived one; sturgeon ancestors had bony skeletons. They also lack vertebral centra, and are partially covered with five lateral rows of scutes rather than scales. They also have four barbels—sensory organs that precede their wide, toothless mouths. They navigate their riverine habitats traveling just off the bottom with their barbels dragging along gravel, or murky substrate. Sturgeon are recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes. The skeletal support for the paired fins of ray finned fish is inside the body wall, although the ray like structures in the webbing of the fins can be seen externally. Sturgeons are among the largest fish: some beluga (Huso huso) in the Caspian Sea reportedly attain over and while for kaluga (H. dauricus) in the Amur River, similar lengths and over weights have been reported. They are also among the longest lived of the fishes, some living well over 100 years and attaining sexual maturity at 20 years or more. The combination of slow growth and reproductive rates and the extremely high value placed on mature, egg bearing females make sturgeon particularly vulnerable to overfishing. Sturgeons are polyploid; some species have four, eight, or 16 sets of chromosomes. Life cycle
Sturgeons are long lived, late maturing fishes. Their average lifespan is 50 to 60 years, and their first spawn does not occur until they are around 15 to 20 years old. Sturgeons are broadcast spawners, and do not spawn every year because they require specific conditions. Those requirements may or may not be met every year due to varying environmental conditions, such as the proper photoperiod in spring, clear water with shallow rock or gravel substrate, where the eggs can adhere, and proper water temperature and flow for oxygenation of the eggs. A single female may release 100,000 to 3 million eggs, but not all will be fertilized. The fertilized eggs become sticky and adhere to the bottom substrate upon contact. Eight to 15 days are needed for the embryos to mature into larval fish. During that time, they are dependent on their yolk sacs for nourishment. River currents carry the larvae downstream into backwater areas, such as oxbows and sloughs, where the free swimming fry spend their first year feeding on insect larvae and crustacea. During their first year of growth, they reach in length and migrate back into the swift flowing currents in the main stem river. Behavior
Sturgeons are primarily benthic feeders, with a diet of shellfish, crustaceans, and small fish. Exceptionally, both Huso'' species, the white sturgeon and the pallid sturgeon feed primarily on other fish as adults. They feed by extending their siphon like mouths to suck food from the benthos. Having no teeth, they are unable to seize prey, though larger individuals and more predatory species can swallow very large prey items, including whole salmon. Sturgeons feed non visually. They are believed to use a combination of sensors, including olfactory, tactile, and chemosensory cues detected by the four barbels, and electroreception using their ampullae of Lorenzini. The electroreceptors are thought to be used in various behaviors such as feeding, mating and migration. Many sturgeons leap completely out of the water, usually making a loud splash which can be heard half a mile away on the surface and probably further under water. Why they do this is not known, but suggested functions include group communication to maintain group cohesion, catching airborne prey, courtship display, or to help shed eggs during spawning. Other plausible explanations include escape from predators, shedding parasites, or to gulp or expel air. Another explanation is that it "simply feels good". in 2015, a 5 year old girl was fatally injured after a sturgeon leapt from the Suwannee River and struck her.
Automatic taxobox
| name = Sturgeon
| image = Acipenser oxyrhynchus (edit). png
| image caption = Atlantic sturgeon(Acipenser oxyrinchus oxyrinchus)
| fossil range =
| taxon = Acipenseridae
| authority = Bonaparte, 1831
| subdivision ranks = Genera
| subdivision =
†Boreiosturion
†Protoscaphirhynchus
†Engdahlichthys
†Anchiacipenser
†Priscosturion
Acipenser (paraphyletic)
Huso
ScaphirhynchusPseudoscaphirhynchus
Sturgeon (from Old English styrġa ultimately from Proto Indo European *str̥(Hx)yón ) is the common name for the 28 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early Jurassic period, some 174 to 201 million years ago. They are one of two living families of the Acipenseriformes alongside paddlefish (Polyodontidae). The family is grouped into four genera: Acipenser (which is paraphyletic, containing many distantly related sturgeon species), Huso, Scaphirhynchus, and Pseudoscaphirhynchus. Two species (A. naccarii and A. dabryanus) may be extinct in the wild, and one (P. fedtschenkoi) may be entirely extinct. Sturgeons are native to subtropical, temperate and sub Arctic rivers, lakes and coastlines of Eurasia and North America. A Maastrichtian age fossil found in Morocco shows that they also once lived in Africa. Sturgeons are long lived, late maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle like body that is smooth skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging in length. The largest sturgeon on record was a beluga female captured in the Volga Delta in 1827, measuring long and weighing Most sturgeons are anadromous bottom feeders, migrating upstream to spawn but spending most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. Several species of sturgeon are harvested for their roe, which is processed into the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction. Evolution
Fossil history
Acipenseriform fishes appeared in the fossil record some 174 to 201 million years ago, during the Early Jurassic, making them some of the earliest extant actinopterygian fishes. True sturgeons appear in the fossil record during the Upper Cretaceous, with amongst the oldest known remains being a partial skull from the Cenomanian (100–94 million years ago) of Alberta, Canada. In that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils. This is explained in part by the long generation interval, tolerance for wide ranges of temperature and salinity, lack of predators due to size and bony plated armor, or scutes, and the abundance of prey items in the benthic environment. They do, however, still share several primitive characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements, and unique jaw suspension. Phylogeny and taxonomy
Despite the existence of a fossil record, full classification and phylogeny of the sturgeon species has been difficult to determine, in part due to the high individual and ontogenic variation, including geographical clines in certain features, such as rostrum shape, number of scutes, and body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. While ray finned fishes (Actinopterygii) have a long evolutionary history culminating in the most familiar fishes, past adaptive evolutionary radiations have left only a few survivors, such as sturgeons and gars. The wide range of the acipenserids and their endangered status have made collection of systematic materials difficult. The factors have led researchers in the past to identify over 40 additional species that were rejected by later scientists. Whether the species in the Acipenser and Huso genera are monophyletic (descended from one ancestor) or paraphyletic (descended from many ancestors) is still unclear, though the morphologically motivated division between these two genera clearly is not supported by the genetic evidence. An effort is ongoing to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques. The phylogeny of Acipenseridae, as in the cladogram, shows that they evolved from the bony fishes. Approximate dates are from Near et al., 2012. However, multiple recent studies have recovered this arrangement as paraphyletic, instead finding A. oxyrhinchus and A. sturio to form the most basal clade among sturgeons, and all other species being in a separate clade, with the various other species of Acipenser, Scaphirhynchus, Pseudoscaphirhynchus, and Huso to have varying levels of relationship with one another. A potential taxonomy of Acipenseridae is shown here, based on Luo et al. 2019, Nedoluzhko et al. 2020, and Shen et al. 2020. Note the paraphyletic relationships among genera:
The exact placement of Scaphirhynchus varies depending on the study and the methods used, with some placing it within the second most basal clade comprising primarily Pacific species (shown above), whereas others place it in its own clade that is more derived than the secondmost basal clade but less derived than the most derived Atlantic and Central Asian clade. No studies have yet delineated a relationship between it and Pseudoscaphirhynchus. In addition, the exact relationships of the members of the most derived, primarily Atlantic clade vary, although most analyses at least find all the species in it to form a monophyletic clade. The placement of A. sinensis also varies by the study, with some placing it as the only Pacific member of the otherwise Atlantic based most derived clade, whereas others place it with the rest of the Pacific sturgeons as a sister to A. dabryanus. in the rivers that flow into the Black, Azov, and Caspian Seas (Danube, Dnepr, Volga, Ural and Don); the north flowing rivers of Russia that feed the Arctic Ocean (Ob, Yenisei, Lena, Kolyma); in the rivers of Central Asia (Amu Darya and Syr Darya) and Lake Baikal. In the Pacific Ocean, they are found in the Amur River along the Russian Chinese border, on Sakhalin Island, and some rivers in northeast China. Most species are at least partially anadromous, spawning in fresh water and feeding in nutrient rich, brackish waters of estuaries or undergoing significant migrations along coastlines. However, some species have evolved purely freshwater existences, such as the lake sturgeon (Acipenser fulvescens) and the Baikal sturgeon (A. baerii baicalensis), or have been forced into them by human or natural impoundment of their native rivers, as in the case of some subpopulations of white sturgeon (A. transmontanus) in the Columbia River and Siberian sturgeon (A. baerii) in the Ob basin. Physical characteristics
Sturgeons retain several primitive characteristics from the bony fishes. Along with other members of the subclass Chondrostei, they are unique among bony fishes because their skeletons are almost entirely cartilaginous. To maintain structure, sturgeons are one of few organisms to retain a post embryonic notochord that acts like a soft spine running through the body. Notably, however, the cartilagineous skeleton is not a primitive character, but a derived one; sturgeon ancestors had bony skeletons. They also lack vertebral centra, and are partially covered with five lateral rows of scutes rather than scales. They also have four barbels—sensory organs that precede their wide, toothless mouths. They navigate their riverine habitats traveling just off the bottom with their barbels dragging along gravel, or murky substrate. Sturgeon are recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes. The skeletal support for the paired fins of ray finned fish is inside the body wall, although the ray like structures in the webbing of the fins can be seen externally. Sturgeons are among the largest fish: some beluga (Huso huso) in the Caspian Sea reportedly attain over and while for kaluga (H. dauricus) in the Amur River, similar lengths and over weights have been reported. They are also among the longest lived of the fishes, some living well over 100 years and attaining sexual maturity at 20 years or more. The combination of slow growth and reproductive rates and the extremely high value placed on mature, egg bearing females make sturgeon particularly vulnerable to overfishing. Sturgeons are polyploid; some species have four, eight, or 16 sets of chromosomes. Life cycle
Sturgeons are long lived, late maturing fishes. Their average lifespan is 50 to 60 years, and their first spawn does not occur until they are around 15 to 20 years old. Sturgeons are broadcast spawners, and do not spawn every year because they require specific conditions. Those requirements may or may not be met every year due to varying environmental conditions, such as the proper photoperiod in spring, clear water with shallow rock or gravel substrate, where the eggs can adhere, and proper water temperature and flow for oxygenation of the eggs. A single female may release 100,000 to 3 million eggs, but not all will be fertilized. The fertilized eggs become sticky and adhere to the bottom substrate upon contact. Eight to 15 days are needed for the embryos to mature into larval fish. During that time, they are dependent on their yolk sacs for nourishment. River currents carry the larvae downstream into backwater areas, such as oxbows and sloughs, where the free swimming fry spend their first year feeding on insect larvae and crustacea. During their first year of growth, they reach in length and migrate back into the swift flowing currents in the main stem river. Behavior
Sturgeons are primarily benthic feeders, with a diet of shellfish, crustaceans, and small fish. Exceptionally, both Huso'' species, the white sturgeon and the pallid sturgeon feed primarily on other fish as adults. They feed by extending their siphon like mouths to suck food from the benthos. Having no teeth, they are unable to seize prey, though larger individuals and more predatory species can swallow very large prey items, including whole salmon. Sturgeons feed non visually. They are believed to use a combination of sensors, including olfactory, tactile, and chemosensory cues detected by the four barbels, and electroreception using their ampullae of Lorenzini. The electroreceptors are thought to be used in various behaviors such as feeding, mating and migration. Many sturgeons leap completely out of the water, usually making a loud splash which can be heard half a mile away on the surface and probably further under water. Why they do this is not known, but suggested functions include group communication to maintain group cohesion, catching airborne prey, courtship display, or to help shed eggs during spawning. Other plausible explanations include escape from predators, shedding parasites, or to gulp or expel air. Another explanation is that it "simply feels good". in 2015, a 5 year old girl was fatally injured after a sturgeon leapt from the Suwannee River and struck her.
Стержон (от древнеанглийского styrġa, восходящего к праиндоевропейскому *str̥(Hx)yón) — общее название для 28 видов рыб, принадлежащих к семейству Acipenseridae. Самые ранние ископаемые остатки осетровых датируются поздним меловым периодом и произошли от других, более ранних аципенсериформных рыб, которые восходят к раннему юрскому периоду, примерно 174–201 миллион лет назад. Они являются одним из двух ныне живущих семейств Acipenseriformes, наряду с рыбами-палками (Polyodontidae). Семейство подразделяется на четыре рода: Acipenser (который является парафилетическим, включающим множество отдалённо родственных видов осетров), Huso, Scaphirhynchus и Pseudoscaphirhynchus. Два вида (A. naccarii и A. dabryanus) могут быть вымершими в дикой природе, а один (P. fedtschenkoi) — полностью вымершим. Стержни обитают в субтропических, умеренных и субарктических реках, озёрах и вдоль побережья Евразии и Северной Америки. Ископаемый образец маастрихтского возраста, найденный в Марокко, свидетельствует о том, что они когда-то обитали и в Африке. Стержни — долгоживущие, поздно созревающие рыбы с характерными особенностями, такими как гетероцеркальный хвостовой плавник, похожий на плавник акул, и удлинённое, веретенообразное тело, покрытое гладкой кожей, лишённой чешуи и защищённое пятью боковыми рядами костных пластин, называемых щитками. Некоторые виды могут достигать значительных размеров, обычно варьируясь в длине. Самый крупный зарегистрированный осетр — самка белуги, пойманная в дельте Волги в 1827 году, длиной и весом . Большинство осетров — анадромы, питающиеся на дне, мигрирующие вверх по течению для нереста, но проводящие большую часть жизни в речных дельтах и эстуариях. Некоторые виды обитают исключительно в пресноводных средах, в то время как другие преимущественно обитают в морских средах вблизи прибрежных зон и заходят в открытый океан. Несколько видов осетров вылавливаются ради их икры, которая перерабатывается в деликатес — икру. Это привело к серьёзному истощению популяции, которое, в сочетании с другими угрозами сохранению, поставило большинство видов на грань вымирания, под угрозой исчезновения.
Ray finned fish
Automatic taxobox
| name = Sturgeon
| image = Acipenser oxyrhynchus (edit). png
| image caption = Atlantic sturgeon(Acipenser oxyrinchus oxyrinchus)
| fossil range =
| taxon = Acipenseridae
| authority = Bonaparte, 1831
| subdivision ranks = Genera
| subdivision =
†Boreiosturion
†Protoscaphirhynchus
†Engdahlichthys
†Anchiacipenser
†Priscosturion
Acipenser (paraphyletic)
Huso
ScaphirhynchusPseudoscaphirhynchus
Sturgeon (from Old English styrġa ultimately from Proto Indo European *str̥(Hx)yón ) is the common name for the 28 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early Jurassic period, some 174 to 201 million years ago. They are one of two living families of the Acipenseriformes alongside paddlefish (Polyodontidae). The family is grouped into four genera: Acipenser (which is paraphyletic, containing many distantly related sturgeon species), Huso, Scaphirhynchus, and Pseudoscaphirhynchus. Two species (A. naccarii and A. dabryanus) may be extinct in the wild, and one (P. fedtschenkoi) may be entirely extinct. Sturgeons are native to subtropical, temperate and sub Arctic rivers, lakes and coastlines of Eurasia and North America. A Maastrichtian age fossil found in Morocco shows that they also once lived in Africa. Sturgeons are long lived, late maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle like body that is smooth skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging in length. The largest sturgeon on record was a beluga female captured in the Volga Delta in 1827, measuring long and weighing Most sturgeons are anadromous bottom feeders, migrating upstream to spawn but spending most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. Several species of sturgeon are harvested for their roe, which is processed into the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction. Evolution
Fossil history
Acipenseriform fishes appeared in the fossil record some 174 to 201 million years ago, during the Early Jurassic, making them some of the earliest extant actinopterygian fishes. True sturgeons appear in the fossil record during the Upper Cretaceous, with amongst the oldest known remains being a partial skull from the Cenomanian (100–94 million years ago) of Alberta, Canada. In that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils. This is explained in part by the long generation interval, tolerance for wide ranges of temperature and salinity, lack of predators due to size and bony plated armor, or scutes, and the abundance of prey items in the benthic environment. They do, however, still share several primitive characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements, and unique jaw suspension. Phylogeny and taxonomy
Despite the existence of a fossil record, full classification and phylogeny of the sturgeon species has been difficult to determine, in part due to the high individual and ontogenic variation, including geographical clines in certain features, such as rostrum shape, number of scutes, and body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. While ray finned fishes (Actinopterygii) have a long evolutionary history culminating in the most familiar fishes, past adaptive evolutionary radiations have left only a few survivors, such as sturgeons and gars. The wide range of the acipenserids and their endangered status have made collection of systematic materials difficult. The factors have led researchers in the past to identify over 40 additional species that were rejected by later scientists. Whether the species in the Acipenser and Huso genera are monophyletic (descended from one ancestor) or paraphyletic (descended from many ancestors) is still unclear, though the morphologically motivated division between these two genera clearly is not supported by the genetic evidence. An effort is ongoing to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques. The phylogeny of Acipenseridae, as in the cladogram, shows that they evolved from the bony fishes. Approximate dates are from Near et al., 2012. However, multiple recent studies have recovered this arrangement as paraphyletic, instead finding A. oxyrhinchus and A. sturio to form the most basal clade among sturgeons, and all other species being in a separate clade, with the various other species of Acipenser, Scaphirhynchus, Pseudoscaphirhynchus, and Huso to have varying levels of relationship with one another. A potential taxonomy of Acipenseridae is shown here, based on Luo et al. 2019, Nedoluzhko et al. 2020, and Shen et al. 2020. Note the paraphyletic relationships among genera:
The exact placement of Scaphirhynchus varies depending on the study and the methods used, with some placing it within the second most basal clade comprising primarily Pacific species (shown above), whereas others place it in its own clade that is more derived than the secondmost basal clade but less derived than the most derived Atlantic and Central Asian clade. No studies have yet delineated a relationship between it and Pseudoscaphirhynchus. In addition, the exact relationships of the members of the most derived, primarily Atlantic clade vary, although most analyses at least find all the species in it to form a monophyletic clade. The placement of A. sinensis also varies by the study, with some placing it as the only Pacific member of the otherwise Atlantic based most derived clade, whereas others place it with the rest of the Pacific sturgeons as a sister to A. dabryanus. in the rivers that flow into the Black, Azov, and Caspian Seas (Danube, Dnepr, Volga, Ural and Don); the north flowing rivers of Russia that feed the Arctic Ocean (Ob, Yenisei, Lena, Kolyma); in the rivers of Central Asia (Amu Darya and Syr Darya) and Lake Baikal. In the Pacific Ocean, they are found in the Amur River along the Russian Chinese border, on Sakhalin Island, and some rivers in northeast China. Most species are at least partially anadromous, spawning in fresh water and feeding in nutrient rich, brackish waters of estuaries or undergoing significant migrations along coastlines. However, some species have evolved purely freshwater existences, such as the lake sturgeon (Acipenser fulvescens) and the Baikal sturgeon (A. baerii baicalensis), or have been forced into them by human or natural impoundment of their native rivers, as in the case of some subpopulations of white sturgeon (A. transmontanus) in the Columbia River and Siberian sturgeon (A. baerii) in the Ob basin. Physical characteristics
Sturgeons retain several primitive characteristics from the bony fishes. Along with other members of the subclass Chondrostei, they are unique among bony fishes because their skeletons are almost entirely cartilaginous. To maintain structure, sturgeons are one of few organisms to retain a post embryonic notochord that acts like a soft spine running through the body. Notably, however, the cartilagineous skeleton is not a primitive character, but a derived one; sturgeon ancestors had bony skeletons. They also lack vertebral centra, and are partially covered with five lateral rows of scutes rather than scales. They also have four barbels—sensory organs that precede their wide, toothless mouths. They navigate their riverine habitats traveling just off the bottom with their barbels dragging along gravel, or murky substrate. Sturgeon are recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes. The skeletal support for the paired fins of ray finned fish is inside the body wall, although the ray like structures in the webbing of the fins can be seen externally. Sturgeons are among the largest fish: some beluga (Huso huso) in the Caspian Sea reportedly attain over and while for kaluga (H. dauricus) in the Amur River, similar lengths and over weights have been reported. They are also among the longest lived of the fishes, some living well over 100 years and attaining sexual maturity at 20 years or more. The combination of slow growth and reproductive rates and the extremely high value placed on mature, egg bearing females make sturgeon particularly vulnerable to overfishing. Sturgeons are polyploid; some species have four, eight, or 16 sets of chromosomes. Life cycle
Sturgeons are long lived, late maturing fishes. Their average lifespan is 50 to 60 years, and their first spawn does not occur until they are around 15 to 20 years old. Sturgeons are broadcast spawners, and do not spawn every year because they require specific conditions. Those requirements may or may not be met every year due to varying environmental conditions, such as the proper photoperiod in spring, clear water with shallow rock or gravel substrate, where the eggs can adhere, and proper water temperature and flow for oxygenation of the eggs. A single female may release 100,000 to 3 million eggs, but not all will be fertilized. The fertilized eggs become sticky and adhere to the bottom substrate upon contact. Eight to 15 days are needed for the embryos to mature into larval fish. During that time, they are dependent on their yolk sacs for nourishment. River currents carry the larvae downstream into backwater areas, such as oxbows and sloughs, where the free swimming fry spend their first year feeding on insect larvae and crustacea. During their first year of growth, they reach in length and migrate back into the swift flowing currents in the main stem river. Behavior
Sturgeons are primarily benthic feeders, with a diet of shellfish, crustaceans, and small fish. Exceptionally, both Huso'' species, the white sturgeon and the pallid sturgeon feed primarily on other fish as adults. They feed by extending their siphon like mouths to suck food from the benthos. Having no teeth, they are unable to seize prey, though larger individuals and more predatory species can swallow very large prey items, including whole salmon. Sturgeons feed non visually. They are believed to use a combination of sensors, including olfactory, tactile, and chemosensory cues detected by the four barbels, and electroreception using their ampullae of Lorenzini. The electroreceptors are thought to be used in various behaviors such as feeding, mating and migration. Many sturgeons leap completely out of the water, usually making a loud splash which can be heard half a mile away on the surface and probably further under water. Why they do this is not known, but suggested functions include group communication to maintain group cohesion, catching airborne prey, courtship display, or to help shed eggs during spawning. Other plausible explanations include escape from predators, shedding parasites, or to gulp or expel air. Another explanation is that it "simply feels good". in 2015, a 5 year old girl was fatally injured after a sturgeon leapt from the Suwannee River and struck her.
Automatic taxobox
| name = Sturgeon
| image = Acipenser oxyrhynchus (edit). png
| image caption = Atlantic sturgeon(Acipenser oxyrinchus oxyrinchus)
| fossil range =
| taxon = Acipenseridae
| authority = Bonaparte, 1831
| subdivision ranks = Genera
| subdivision =
†Boreiosturion
†Protoscaphirhynchus
†Engdahlichthys
†Anchiacipenser
†Priscosturion
Acipenser (paraphyletic)
Huso
ScaphirhynchusPseudoscaphirhynchus
Sturgeon (from Old English styrġa ultimately from Proto Indo European *str̥(Hx)yón ) is the common name for the 28 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early Jurassic period, some 174 to 201 million years ago. They are one of two living families of the Acipenseriformes alongside paddlefish (Polyodontidae). The family is grouped into four genera: Acipenser (which is paraphyletic, containing many distantly related sturgeon species), Huso, Scaphirhynchus, and Pseudoscaphirhynchus. Two species (A. naccarii and A. dabryanus) may be extinct in the wild, and one (P. fedtschenkoi) may be entirely extinct. Sturgeons are native to subtropical, temperate and sub Arctic rivers, lakes and coastlines of Eurasia and North America. A Maastrichtian age fossil found in Morocco shows that they also once lived in Africa. Sturgeons are long lived, late maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle like body that is smooth skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging in length. The largest sturgeon on record was a beluga female captured in the Volga Delta in 1827, measuring long and weighing Most sturgeons are anadromous bottom feeders, migrating upstream to spawn but spending most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. Several species of sturgeon are harvested for their roe, which is processed into the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction. Evolution
Fossil history
Acipenseriform fishes appeared in the fossil record some 174 to 201 million years ago, during the Early Jurassic, making them some of the earliest extant actinopterygian fishes. True sturgeons appear in the fossil record during the Upper Cretaceous, with amongst the oldest known remains being a partial skull from the Cenomanian (100–94 million years ago) of Alberta, Canada. In that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils. This is explained in part by the long generation interval, tolerance for wide ranges of temperature and salinity, lack of predators due to size and bony plated armor, or scutes, and the abundance of prey items in the benthic environment. They do, however, still share several primitive characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements, and unique jaw suspension. Phylogeny and taxonomy
Despite the existence of a fossil record, full classification and phylogeny of the sturgeon species has been difficult to determine, in part due to the high individual and ontogenic variation, including geographical clines in certain features, such as rostrum shape, number of scutes, and body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. While ray finned fishes (Actinopterygii) have a long evolutionary history culminating in the most familiar fishes, past adaptive evolutionary radiations have left only a few survivors, such as sturgeons and gars. The wide range of the acipenserids and their endangered status have made collection of systematic materials difficult. The factors have led researchers in the past to identify over 40 additional species that were rejected by later scientists. Whether the species in the Acipenser and Huso genera are monophyletic (descended from one ancestor) or paraphyletic (descended from many ancestors) is still unclear, though the morphologically motivated division between these two genera clearly is not supported by the genetic evidence. An effort is ongoing to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques. The phylogeny of Acipenseridae, as in the cladogram, shows that they evolved from the bony fishes. Approximate dates are from Near et al., 2012. However, multiple recent studies have recovered this arrangement as paraphyletic, instead finding A. oxyrhinchus and A. sturio to form the most basal clade among sturgeons, and all other species being in a separate clade, with the various other species of Acipenser, Scaphirhynchus, Pseudoscaphirhynchus, and Huso to have varying levels of relationship with one another. A potential taxonomy of Acipenseridae is shown here, based on Luo et al. 2019, Nedoluzhko et al. 2020, and Shen et al. 2020. Note the paraphyletic relationships among genera:
The exact placement of Scaphirhynchus varies depending on the study and the methods used, with some placing it within the second most basal clade comprising primarily Pacific species (shown above), whereas others place it in its own clade that is more derived than the secondmost basal clade but less derived than the most derived Atlantic and Central Asian clade. No studies have yet delineated a relationship between it and Pseudoscaphirhynchus. In addition, the exact relationships of the members of the most derived, primarily Atlantic clade vary, although most analyses at least find all the species in it to form a monophyletic clade. The placement of A. sinensis also varies by the study, with some placing it as the only Pacific member of the otherwise Atlantic based most derived clade, whereas others place it with the rest of the Pacific sturgeons as a sister to A. dabryanus. in the rivers that flow into the Black, Azov, and Caspian Seas (Danube, Dnepr, Volga, Ural and Don); the north flowing rivers of Russia that feed the Arctic Ocean (Ob, Yenisei, Lena, Kolyma); in the rivers of Central Asia (Amu Darya and Syr Darya) and Lake Baikal. In the Pacific Ocean, they are found in the Amur River along the Russian Chinese border, on Sakhalin Island, and some rivers in northeast China. Most species are at least partially anadromous, spawning in fresh water and feeding in nutrient rich, brackish waters of estuaries or undergoing significant migrations along coastlines. However, some species have evolved purely freshwater existences, such as the lake sturgeon (Acipenser fulvescens) and the Baikal sturgeon (A. baerii baicalensis), or have been forced into them by human or natural impoundment of their native rivers, as in the case of some subpopulations of white sturgeon (A. transmontanus) in the Columbia River and Siberian sturgeon (A. baerii) in the Ob basin. Physical characteristics
Sturgeons retain several primitive characteristics from the bony fishes. Along with other members of the subclass Chondrostei, they are unique among bony fishes because their skeletons are almost entirely cartilaginous. To maintain structure, sturgeons are one of few organisms to retain a post embryonic notochord that acts like a soft spine running through the body. Notably, however, the cartilagineous skeleton is not a primitive character, but a derived one; sturgeon ancestors had bony skeletons. They also lack vertebral centra, and are partially covered with five lateral rows of scutes rather than scales. They also have four barbels—sensory organs that precede their wide, toothless mouths. They navigate their riverine habitats traveling just off the bottom with their barbels dragging along gravel, or murky substrate. Sturgeon are recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes. The skeletal support for the paired fins of ray finned fish is inside the body wall, although the ray like structures in the webbing of the fins can be seen externally. Sturgeons are among the largest fish: some beluga (Huso huso) in the Caspian Sea reportedly attain over and while for kaluga (H. dauricus) in the Amur River, similar lengths and over weights have been reported. They are also among the longest lived of the fishes, some living well over 100 years and attaining sexual maturity at 20 years or more. The combination of slow growth and reproductive rates and the extremely high value placed on mature, egg bearing females make sturgeon particularly vulnerable to overfishing. Sturgeons are polyploid; some species have four, eight, or 16 sets of chromosomes. Life cycle
Sturgeons are long lived, late maturing fishes. Their average lifespan is 50 to 60 years, and their first spawn does not occur until they are around 15 to 20 years old. Sturgeons are broadcast spawners, and do not spawn every year because they require specific conditions. Those requirements may or may not be met every year due to varying environmental conditions, such as the proper photoperiod in spring, clear water with shallow rock or gravel substrate, where the eggs can adhere, and proper water temperature and flow for oxygenation of the eggs. A single female may release 100,000 to 3 million eggs, but not all will be fertilized. The fertilized eggs become sticky and adhere to the bottom substrate upon contact. Eight to 15 days are needed for the embryos to mature into larval fish. During that time, they are dependent on their yolk sacs for nourishment. River currents carry the larvae downstream into backwater areas, such as oxbows and sloughs, where the free swimming fry spend their first year feeding on insect larvae and crustacea. During their first year of growth, they reach in length and migrate back into the swift flowing currents in the main stem river. Behavior
Sturgeons are primarily benthic feeders, with a diet of shellfish, crustaceans, and small fish. Exceptionally, both Huso'' species, the white sturgeon and the pallid sturgeon feed primarily on other fish as adults. They feed by extending their siphon like mouths to suck food from the benthos. Having no teeth, they are unable to seize prey, though larger individuals and more predatory species can swallow very large prey items, including whole salmon. Sturgeons feed non visually. They are believed to use a combination of sensors, including olfactory, tactile, and chemosensory cues detected by the four barbels, and electroreception using their ampullae of Lorenzini. The electroreceptors are thought to be used in various behaviors such as feeding, mating and migration. Many sturgeons leap completely out of the water, usually making a loud splash which can be heard half a mile away on the surface and probably further under water. Why they do this is not known, but suggested functions include group communication to maintain group cohesion, catching airborne prey, courtship display, or to help shed eggs during spawning. Other plausible explanations include escape from predators, shedding parasites, or to gulp or expel air. Another explanation is that it "simply feels good". in 2015, a 5 year old girl was fatally injured after a sturgeon leapt from the Suwannee River and struck her.
Эволюция
Ray finned fish
Automatic taxobox
| name = Sturgeon
| image = Acipenser oxyrhynchus (edit). png
| image caption = Atlantic sturgeon(Acipenser oxyrinchus oxyrinchus)
| fossil range =
| taxon = Acipenseridae
| authority = Bonaparte, 1831
| subdivision ranks = Genera
| subdivision =
†Boreiosturion
†Protoscaphirhynchus
†Engdahlichthys
†Anchiacipenser
†Priscosturion
Acipenser (paraphyletic)
Huso
ScaphirhynchusPseudoscaphirhynchus
Sturgeon (from Old English styrġa ultimately from Proto Indo European *str̥(Hx)yón ) is the common name for the 28 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early Jurassic period, some 174 to 201 million years ago. They are one of two living families of the Acipenseriformes alongside paddlefish (Polyodontidae). The family is grouped into four genera: Acipenser (which is paraphyletic, containing many distantly related sturgeon species), Huso, Scaphirhynchus, and Pseudoscaphirhynchus. Two species (A. naccarii and A. dabryanus) may be extinct in the wild, and one (P. fedtschenkoi) may be entirely extinct. Sturgeons are native to subtropical, temperate and sub Arctic rivers, lakes and coastlines of Eurasia and North America. A Maastrichtian age fossil found in Morocco shows that they also once lived in Africa. Sturgeons are long lived, late maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle like body that is smooth skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging in length. The largest sturgeon on record was a beluga female captured in the Volga Delta in 1827, measuring long and weighing Most sturgeons are anadromous bottom feeders, migrating upstream to spawn but spending most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. Several species of sturgeon are harvested for their roe, which is processed into the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction. Evolution
Fossil history
Acipenseriform fishes appeared in the fossil record some 174 to 201 million years ago, during the Early Jurassic, making them some of the earliest extant actinopterygian fishes. True sturgeons appear in the fossil record during the Upper Cretaceous, with amongst the oldest known remains being a partial skull from the Cenomanian (100–94 million years ago) of Alberta, Canada. In that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils. This is explained in part by the long generation interval, tolerance for wide ranges of temperature and salinity, lack of predators due to size and bony plated armor, or scutes, and the abundance of prey items in the benthic environment. They do, however, still share several primitive characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements, and unique jaw suspension. Phylogeny and taxonomy
Despite the existence of a fossil record, full classification and phylogeny of the sturgeon species has been difficult to determine, in part due to the high individual and ontogenic variation, including geographical clines in certain features, such as rostrum shape, number of scutes, and body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. While ray finned fishes (Actinopterygii) have a long evolutionary history culminating in the most familiar fishes, past adaptive evolutionary radiations have left only a few survivors, such as sturgeons and gars. The wide range of the acipenserids and their endangered status have made collection of systematic materials difficult. The factors have led researchers in the past to identify over 40 additional species that were rejected by later scientists. Whether the species in the Acipenser and Huso genera are monophyletic (descended from one ancestor) or paraphyletic (descended from many ancestors) is still unclear, though the morphologically motivated division between these two genera clearly is not supported by the genetic evidence. An effort is ongoing to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques. The phylogeny of Acipenseridae, as in the cladogram, shows that they evolved from the bony fishes. Approximate dates are from Near et al., 2012. However, multiple recent studies have recovered this arrangement as paraphyletic, instead finding A. oxyrhinchus and A. sturio to form the most basal clade among sturgeons, and all other species being in a separate clade, with the various other species of Acipenser, Scaphirhynchus, Pseudoscaphirhynchus, and Huso to have varying levels of relationship with one another. A potential taxonomy of Acipenseridae is shown here, based on Luo et al. 2019, Nedoluzhko et al. 2020, and Shen et al. 2020. Note the paraphyletic relationships among genera:
The exact placement of Scaphirhynchus varies depending on the study and the methods used, with some placing it within the second most basal clade comprising primarily Pacific species (shown above), whereas others place it in its own clade that is more derived than the secondmost basal clade but less derived than the most derived Atlantic and Central Asian clade. No studies have yet delineated a relationship between it and Pseudoscaphirhynchus. In addition, the exact relationships of the members of the most derived, primarily Atlantic clade vary, although most analyses at least find all the species in it to form a monophyletic clade. The placement of A. sinensis also varies by the study, with some placing it as the only Pacific member of the otherwise Atlantic based most derived clade, whereas others place it with the rest of the Pacific sturgeons as a sister to A. dabryanus. in the rivers that flow into the Black, Azov, and Caspian Seas (Danube, Dnepr, Volga, Ural and Don); the north flowing rivers of Russia that feed the Arctic Ocean (Ob, Yenisei, Lena, Kolyma); in the rivers of Central Asia (Amu Darya and Syr Darya) and Lake Baikal. In the Pacific Ocean, they are found in the Amur River along the Russian Chinese border, on Sakhalin Island, and some rivers in northeast China. Most species are at least partially anadromous, spawning in fresh water and feeding in nutrient rich, brackish waters of estuaries or undergoing significant migrations along coastlines. However, some species have evolved purely freshwater existences, such as the lake sturgeon (Acipenser fulvescens) and the Baikal sturgeon (A. baerii baicalensis), or have been forced into them by human or natural impoundment of their native rivers, as in the case of some subpopulations of white sturgeon (A. transmontanus) in the Columbia River and Siberian sturgeon (A. baerii) in the Ob basin. Physical characteristics
Sturgeons retain several primitive characteristics from the bony fishes. Along with other members of the subclass Chondrostei, they are unique among bony fishes because their skeletons are almost entirely cartilaginous. To maintain structure, sturgeons are one of few organisms to retain a post embryonic notochord that acts like a soft spine running through the body. Notably, however, the cartilagineous skeleton is not a primitive character, but a derived one; sturgeon ancestors had bony skeletons. They also lack vertebral centra, and are partially covered with five lateral rows of scutes rather than scales. They also have four barbels—sensory organs that precede their wide, toothless mouths. They navigate their riverine habitats traveling just off the bottom with their barbels dragging along gravel, or murky substrate. Sturgeon are recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes. The skeletal support for the paired fins of ray finned fish is inside the body wall, although the ray like structures in the webbing of the fins can be seen externally. Sturgeons are among the largest fish: some beluga (Huso huso) in the Caspian Sea reportedly attain over and while for kaluga (H. dauricus) in the Amur River, similar lengths and over weights have been reported. They are also among the longest lived of the fishes, some living well over 100 years and attaining sexual maturity at 20 years or more. The combination of slow growth and reproductive rates and the extremely high value placed on mature, egg bearing females make sturgeon particularly vulnerable to overfishing. Sturgeons are polyploid; some species have four, eight, or 16 sets of chromosomes. Life cycle
Sturgeons are long lived, late maturing fishes. Their average lifespan is 50 to 60 years, and their first spawn does not occur until they are around 15 to 20 years old. Sturgeons are broadcast spawners, and do not spawn every year because they require specific conditions. Those requirements may or may not be met every year due to varying environmental conditions, such as the proper photoperiod in spring, clear water with shallow rock or gravel substrate, where the eggs can adhere, and proper water temperature and flow for oxygenation of the eggs. A single female may release 100,000 to 3 million eggs, but not all will be fertilized. The fertilized eggs become sticky and adhere to the bottom substrate upon contact. Eight to 15 days are needed for the embryos to mature into larval fish. During that time, they are dependent on their yolk sacs for nourishment. River currents carry the larvae downstream into backwater areas, such as oxbows and sloughs, where the free swimming fry spend their first year feeding on insect larvae and crustacea. During their first year of growth, they reach in length and migrate back into the swift flowing currents in the main stem river. Behavior
Sturgeons are primarily benthic feeders, with a diet of shellfish, crustaceans, and small fish. Exceptionally, both Huso'' species, the white sturgeon and the pallid sturgeon feed primarily on other fish as adults. They feed by extending their siphon like mouths to suck food from the benthos. Having no teeth, they are unable to seize prey, though larger individuals and more predatory species can swallow very large prey items, including whole salmon. Sturgeons feed non visually. They are believed to use a combination of sensors, including olfactory, tactile, and chemosensory cues detected by the four barbels, and electroreception using their ampullae of Lorenzini. The electroreceptors are thought to be used in various behaviors such as feeding, mating and migration. Many sturgeons leap completely out of the water, usually making a loud splash which can be heard half a mile away on the surface and probably further under water. Why they do this is not known, but suggested functions include group communication to maintain group cohesion, catching airborne prey, courtship display, or to help shed eggs during spawning. Other plausible explanations include escape from predators, shedding parasites, or to gulp or expel air. Another explanation is that it "simply feels good". in 2015, a 5 year old girl was fatally injured after a sturgeon leapt from the Suwannee River and struck her.
Automatic taxobox
| name = Sturgeon
| image = Acipenser oxyrhynchus (edit). png
| image caption = Atlantic sturgeon(Acipenser oxyrinchus oxyrinchus)
| fossil range =
| taxon = Acipenseridae
| authority = Bonaparte, 1831
| subdivision ranks = Genera
| subdivision =
†Boreiosturion
†Protoscaphirhynchus
†Engdahlichthys
†Anchiacipenser
†Priscosturion
Acipenser (paraphyletic)
Huso
ScaphirhynchusPseudoscaphirhynchus
Sturgeon (from Old English styrġa ultimately from Proto Indo European *str̥(Hx)yón ) is the common name for the 28 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early Jurassic period, some 174 to 201 million years ago. They are one of two living families of the Acipenseriformes alongside paddlefish (Polyodontidae). The family is grouped into four genera: Acipenser (which is paraphyletic, containing many distantly related sturgeon species), Huso, Scaphirhynchus, and Pseudoscaphirhynchus. Two species (A. naccarii and A. dabryanus) may be extinct in the wild, and one (P. fedtschenkoi) may be entirely extinct. Sturgeons are native to subtropical, temperate and sub Arctic rivers, lakes and coastlines of Eurasia and North America. A Maastrichtian age fossil found in Morocco shows that they also once lived in Africa. Sturgeons are long lived, late maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle like body that is smooth skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging in length. The largest sturgeon on record was a beluga female captured in the Volga Delta in 1827, measuring long and weighing Most sturgeons are anadromous bottom feeders, migrating upstream to spawn but spending most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. Several species of sturgeon are harvested for their roe, which is processed into the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction. Evolution
Fossil history
Acipenseriform fishes appeared in the fossil record some 174 to 201 million years ago, during the Early Jurassic, making them some of the earliest extant actinopterygian fishes. True sturgeons appear in the fossil record during the Upper Cretaceous, with amongst the oldest known remains being a partial skull from the Cenomanian (100–94 million years ago) of Alberta, Canada. In that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils. This is explained in part by the long generation interval, tolerance for wide ranges of temperature and salinity, lack of predators due to size and bony plated armor, or scutes, and the abundance of prey items in the benthic environment. They do, however, still share several primitive characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements, and unique jaw suspension. Phylogeny and taxonomy
Despite the existence of a fossil record, full classification and phylogeny of the sturgeon species has been difficult to determine, in part due to the high individual and ontogenic variation, including geographical clines in certain features, such as rostrum shape, number of scutes, and body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. While ray finned fishes (Actinopterygii) have a long evolutionary history culminating in the most familiar fishes, past adaptive evolutionary radiations have left only a few survivors, such as sturgeons and gars. The wide range of the acipenserids and their endangered status have made collection of systematic materials difficult. The factors have led researchers in the past to identify over 40 additional species that were rejected by later scientists. Whether the species in the Acipenser and Huso genera are monophyletic (descended from one ancestor) or paraphyletic (descended from many ancestors) is still unclear, though the morphologically motivated division between these two genera clearly is not supported by the genetic evidence. An effort is ongoing to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques. The phylogeny of Acipenseridae, as in the cladogram, shows that they evolved from the bony fishes. Approximate dates are from Near et al., 2012. However, multiple recent studies have recovered this arrangement as paraphyletic, instead finding A. oxyrhinchus and A. sturio to form the most basal clade among sturgeons, and all other species being in a separate clade, with the various other species of Acipenser, Scaphirhynchus, Pseudoscaphirhynchus, and Huso to have varying levels of relationship with one another. A potential taxonomy of Acipenseridae is shown here, based on Luo et al. 2019, Nedoluzhko et al. 2020, and Shen et al. 2020. Note the paraphyletic relationships among genera:
The exact placement of Scaphirhynchus varies depending on the study and the methods used, with some placing it within the second most basal clade comprising primarily Pacific species (shown above), whereas others place it in its own clade that is more derived than the secondmost basal clade but less derived than the most derived Atlantic and Central Asian clade. No studies have yet delineated a relationship between it and Pseudoscaphirhynchus. In addition, the exact relationships of the members of the most derived, primarily Atlantic clade vary, although most analyses at least find all the species in it to form a monophyletic clade. The placement of A. sinensis also varies by the study, with some placing it as the only Pacific member of the otherwise Atlantic based most derived clade, whereas others place it with the rest of the Pacific sturgeons as a sister to A. dabryanus. in the rivers that flow into the Black, Azov, and Caspian Seas (Danube, Dnepr, Volga, Ural and Don); the north flowing rivers of Russia that feed the Arctic Ocean (Ob, Yenisei, Lena, Kolyma); in the rivers of Central Asia (Amu Darya and Syr Darya) and Lake Baikal. In the Pacific Ocean, they are found in the Amur River along the Russian Chinese border, on Sakhalin Island, and some rivers in northeast China. Most species are at least partially anadromous, spawning in fresh water and feeding in nutrient rich, brackish waters of estuaries or undergoing significant migrations along coastlines. However, some species have evolved purely freshwater existences, such as the lake sturgeon (Acipenser fulvescens) and the Baikal sturgeon (A. baerii baicalensis), or have been forced into them by human or natural impoundment of their native rivers, as in the case of some subpopulations of white sturgeon (A. transmontanus) in the Columbia River and Siberian sturgeon (A. baerii) in the Ob basin. Physical characteristics
Sturgeons retain several primitive characteristics from the bony fishes. Along with other members of the subclass Chondrostei, they are unique among bony fishes because their skeletons are almost entirely cartilaginous. To maintain structure, sturgeons are one of few organisms to retain a post embryonic notochord that acts like a soft spine running through the body. Notably, however, the cartilagineous skeleton is not a primitive character, but a derived one; sturgeon ancestors had bony skeletons. They also lack vertebral centra, and are partially covered with five lateral rows of scutes rather than scales. They also have four barbels—sensory organs that precede their wide, toothless mouths. They navigate their riverine habitats traveling just off the bottom with their barbels dragging along gravel, or murky substrate. Sturgeon are recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes. The skeletal support for the paired fins of ray finned fish is inside the body wall, although the ray like structures in the webbing of the fins can be seen externally. Sturgeons are among the largest fish: some beluga (Huso huso) in the Caspian Sea reportedly attain over and while for kaluga (H. dauricus) in the Amur River, similar lengths and over weights have been reported. They are also among the longest lived of the fishes, some living well over 100 years and attaining sexual maturity at 20 years or more. The combination of slow growth and reproductive rates and the extremely high value placed on mature, egg bearing females make sturgeon particularly vulnerable to overfishing. Sturgeons are polyploid; some species have four, eight, or 16 sets of chromosomes. Life cycle
Sturgeons are long lived, late maturing fishes. Their average lifespan is 50 to 60 years, and their first spawn does not occur until they are around 15 to 20 years old. Sturgeons are broadcast spawners, and do not spawn every year because they require specific conditions. Those requirements may or may not be met every year due to varying environmental conditions, such as the proper photoperiod in spring, clear water with shallow rock or gravel substrate, where the eggs can adhere, and proper water temperature and flow for oxygenation of the eggs. A single female may release 100,000 to 3 million eggs, but not all will be fertilized. The fertilized eggs become sticky and adhere to the bottom substrate upon contact. Eight to 15 days are needed for the embryos to mature into larval fish. During that time, they are dependent on their yolk sacs for nourishment. River currents carry the larvae downstream into backwater areas, such as oxbows and sloughs, where the free swimming fry spend their first year feeding on insect larvae and crustacea. During their first year of growth, they reach in length and migrate back into the swift flowing currents in the main stem river. Behavior
Sturgeons are primarily benthic feeders, with a diet of shellfish, crustaceans, and small fish. Exceptionally, both Huso'' species, the white sturgeon and the pallid sturgeon feed primarily on other fish as adults. They feed by extending their siphon like mouths to suck food from the benthos. Having no teeth, they are unable to seize prey, though larger individuals and more predatory species can swallow very large prey items, including whole salmon. Sturgeons feed non visually. They are believed to use a combination of sensors, including olfactory, tactile, and chemosensory cues detected by the four barbels, and electroreception using their ampullae of Lorenzini. The electroreceptors are thought to be used in various behaviors such as feeding, mating and migration. Many sturgeons leap completely out of the water, usually making a loud splash which can be heard half a mile away on the surface and probably further under water. Why they do this is not known, but suggested functions include group communication to maintain group cohesion, catching airborne prey, courtship display, or to help shed eggs during spawning. Other plausible explanations include escape from predators, shedding parasites, or to gulp or expel air. Another explanation is that it "simply feels good". in 2015, a 5 year old girl was fatally injured after a sturgeon leapt from the Suwannee River and struck her.
История ископаемых
Ray finned fish
Automatic taxobox
| name = Sturgeon
| image = Acipenser oxyrhynchus (edit). png
| image caption = Atlantic sturgeon(Acipenser oxyrinchus oxyrinchus)
| fossil range =
| taxon = Acipenseridae
| authority = Bonaparte, 1831
| subdivision ranks = Genera
| subdivision =
†Boreiosturion
†Protoscaphirhynchus
†Engdahlichthys
†Anchiacipenser
†Priscosturion
Acipenser (paraphyletic)
Huso
ScaphirhynchusPseudoscaphirhynchus
Sturgeon (from Old English styrġa ultimately from Proto Indo European *str̥(Hx)yón ) is the common name for the 28 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early Jurassic period, some 174 to 201 million years ago. They are one of two living families of the Acipenseriformes alongside paddlefish (Polyodontidae). The family is grouped into four genera: Acipenser (which is paraphyletic, containing many distantly related sturgeon species), Huso, Scaphirhynchus, and Pseudoscaphirhynchus. Two species (A. naccarii and A. dabryanus) may be extinct in the wild, and one (P. fedtschenkoi) may be entirely extinct. Sturgeons are native to subtropical, temperate and sub Arctic rivers, lakes and coastlines of Eurasia and North America. A Maastrichtian age fossil found in Morocco shows that they also once lived in Africa. Sturgeons are long lived, late maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle like body that is smooth skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging in length. The largest sturgeon on record was a beluga female captured in the Volga Delta in 1827, measuring long and weighing Most sturgeons are anadromous bottom feeders, migrating upstream to spawn but spending most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. Several species of sturgeon are harvested for their roe, which is processed into the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction. Evolution
Fossil history
Acipenseriform fishes appeared in the fossil record some 174 to 201 million years ago, during the Early Jurassic, making them some of the earliest extant actinopterygian fishes. True sturgeons appear in the fossil record during the Upper Cretaceous, with amongst the oldest known remains being a partial skull from the Cenomanian (100–94 million years ago) of Alberta, Canada. In that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils. This is explained in part by the long generation interval, tolerance for wide ranges of temperature and salinity, lack of predators due to size and bony plated armor, or scutes, and the abundance of prey items in the benthic environment. They do, however, still share several primitive characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements, and unique jaw suspension. Phylogeny and taxonomy
Despite the existence of a fossil record, full classification and phylogeny of the sturgeon species has been difficult to determine, in part due to the high individual and ontogenic variation, including geographical clines in certain features, such as rostrum shape, number of scutes, and body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. While ray finned fishes (Actinopterygii) have a long evolutionary history culminating in the most familiar fishes, past adaptive evolutionary radiations have left only a few survivors, such as sturgeons and gars. The wide range of the acipenserids and their endangered status have made collection of systematic materials difficult. The factors have led researchers in the past to identify over 40 additional species that were rejected by later scientists. Whether the species in the Acipenser and Huso genera are monophyletic (descended from one ancestor) or paraphyletic (descended from many ancestors) is still unclear, though the morphologically motivated division between these two genera clearly is not supported by the genetic evidence. An effort is ongoing to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques. The phylogeny of Acipenseridae, as in the cladogram, shows that they evolved from the bony fishes. Approximate dates are from Near et al., 2012. However, multiple recent studies have recovered this arrangement as paraphyletic, instead finding A. oxyrhinchus and A. sturio to form the most basal clade among sturgeons, and all other species being in a separate clade, with the various other species of Acipenser, Scaphirhynchus, Pseudoscaphirhynchus, and Huso to have varying levels of relationship with one another. A potential taxonomy of Acipenseridae is shown here, based on Luo et al. 2019, Nedoluzhko et al. 2020, and Shen et al. 2020. Note the paraphyletic relationships among genera:
The exact placement of Scaphirhynchus varies depending on the study and the methods used, with some placing it within the second most basal clade comprising primarily Pacific species (shown above), whereas others place it in its own clade that is more derived than the secondmost basal clade but less derived than the most derived Atlantic and Central Asian clade. No studies have yet delineated a relationship between it and Pseudoscaphirhynchus. In addition, the exact relationships of the members of the most derived, primarily Atlantic clade vary, although most analyses at least find all the species in it to form a monophyletic clade. The placement of A. sinensis also varies by the study, with some placing it as the only Pacific member of the otherwise Atlantic based most derived clade, whereas others place it with the rest of the Pacific sturgeons as a sister to A. dabryanus. in the rivers that flow into the Black, Azov, and Caspian Seas (Danube, Dnepr, Volga, Ural and Don); the north flowing rivers of Russia that feed the Arctic Ocean (Ob, Yenisei, Lena, Kolyma); in the rivers of Central Asia (Amu Darya and Syr Darya) and Lake Baikal. In the Pacific Ocean, they are found in the Amur River along the Russian Chinese border, on Sakhalin Island, and some rivers in northeast China. Most species are at least partially anadromous, spawning in fresh water and feeding in nutrient rich, brackish waters of estuaries or undergoing significant migrations along coastlines. However, some species have evolved purely freshwater existences, such as the lake sturgeon (Acipenser fulvescens) and the Baikal sturgeon (A. baerii baicalensis), or have been forced into them by human or natural impoundment of their native rivers, as in the case of some subpopulations of white sturgeon (A. transmontanus) in the Columbia River and Siberian sturgeon (A. baerii) in the Ob basin. Physical characteristics
Sturgeons retain several primitive characteristics from the bony fishes. Along with other members of the subclass Chondrostei, they are unique among bony fishes because their skeletons are almost entirely cartilaginous. To maintain structure, sturgeons are one of few organisms to retain a post embryonic notochord that acts like a soft spine running through the body. Notably, however, the cartilagineous skeleton is not a primitive character, but a derived one; sturgeon ancestors had bony skeletons. They also lack vertebral centra, and are partially covered with five lateral rows of scutes rather than scales. They also have four barbels—sensory organs that precede their wide, toothless mouths. They navigate their riverine habitats traveling just off the bottom with their barbels dragging along gravel, or murky substrate. Sturgeon are recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes. The skeletal support for the paired fins of ray finned fish is inside the body wall, although the ray like structures in the webbing of the fins can be seen externally. Sturgeons are among the largest fish: some beluga (Huso huso) in the Caspian Sea reportedly attain over and while for kaluga (H. dauricus) in the Amur River, similar lengths and over weights have been reported. They are also among the longest lived of the fishes, some living well over 100 years and attaining sexual maturity at 20 years or more. The combination of slow growth and reproductive rates and the extremely high value placed on mature, egg bearing females make sturgeon particularly vulnerable to overfishing. Sturgeons are polyploid; some species have four, eight, or 16 sets of chromosomes. Life cycle
Sturgeons are long lived, late maturing fishes. Their average lifespan is 50 to 60 years, and their first spawn does not occur until they are around 15 to 20 years old. Sturgeons are broadcast spawners, and do not spawn every year because they require specific conditions. Those requirements may or may not be met every year due to varying environmental conditions, such as the proper photoperiod in spring, clear water with shallow rock or gravel substrate, where the eggs can adhere, and proper water temperature and flow for oxygenation of the eggs. A single female may release 100,000 to 3 million eggs, but not all will be fertilized. The fertilized eggs become sticky and adhere to the bottom substrate upon contact. Eight to 15 days are needed for the embryos to mature into larval fish. During that time, they are dependent on their yolk sacs for nourishment. River currents carry the larvae downstream into backwater areas, such as oxbows and sloughs, where the free swimming fry spend their first year feeding on insect larvae and crustacea. During their first year of growth, they reach in length and migrate back into the swift flowing currents in the main stem river. Behavior
Sturgeons are primarily benthic feeders, with a diet of shellfish, crustaceans, and small fish. Exceptionally, both Huso'' species, the white sturgeon and the pallid sturgeon feed primarily on other fish as adults. They feed by extending their siphon like mouths to suck food from the benthos. Having no teeth, they are unable to seize prey, though larger individuals and more predatory species can swallow very large prey items, including whole salmon. Sturgeons feed non visually. They are believed to use a combination of sensors, including olfactory, tactile, and chemosensory cues detected by the four barbels, and electroreception using their ampullae of Lorenzini. The electroreceptors are thought to be used in various behaviors such as feeding, mating and migration. Many sturgeons leap completely out of the water, usually making a loud splash which can be heard half a mile away on the surface and probably further under water. Why they do this is not known, but suggested functions include group communication to maintain group cohesion, catching airborne prey, courtship display, or to help shed eggs during spawning. Other plausible explanations include escape from predators, shedding parasites, or to gulp or expel air. Another explanation is that it "simply feels good". in 2015, a 5 year old girl was fatally injured after a sturgeon leapt from the Suwannee River and struck her.
Automatic taxobox
| name = Sturgeon
| image = Acipenser oxyrhynchus (edit). png
| image caption = Atlantic sturgeon(Acipenser oxyrinchus oxyrinchus)
| fossil range =
| taxon = Acipenseridae
| authority = Bonaparte, 1831
| subdivision ranks = Genera
| subdivision =
†Boreiosturion
†Protoscaphirhynchus
†Engdahlichthys
†Anchiacipenser
†Priscosturion
Acipenser (paraphyletic)
Huso
ScaphirhynchusPseudoscaphirhynchus
Sturgeon (from Old English styrġa ultimately from Proto Indo European *str̥(Hx)yón ) is the common name for the 28 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early Jurassic period, some 174 to 201 million years ago. They are one of two living families of the Acipenseriformes alongside paddlefish (Polyodontidae). The family is grouped into four genera: Acipenser (which is paraphyletic, containing many distantly related sturgeon species), Huso, Scaphirhynchus, and Pseudoscaphirhynchus. Two species (A. naccarii and A. dabryanus) may be extinct in the wild, and one (P. fedtschenkoi) may be entirely extinct. Sturgeons are native to subtropical, temperate and sub Arctic rivers, lakes and coastlines of Eurasia and North America. A Maastrichtian age fossil found in Morocco shows that they also once lived in Africa. Sturgeons are long lived, late maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle like body that is smooth skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging in length. The largest sturgeon on record was a beluga female captured in the Volga Delta in 1827, measuring long and weighing Most sturgeons are anadromous bottom feeders, migrating upstream to spawn but spending most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. Several species of sturgeon are harvested for their roe, which is processed into the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction. Evolution
Fossil history
Acipenseriform fishes appeared in the fossil record some 174 to 201 million years ago, during the Early Jurassic, making them some of the earliest extant actinopterygian fishes. True sturgeons appear in the fossil record during the Upper Cretaceous, with amongst the oldest known remains being a partial skull from the Cenomanian (100–94 million years ago) of Alberta, Canada. In that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils. This is explained in part by the long generation interval, tolerance for wide ranges of temperature and salinity, lack of predators due to size and bony plated armor, or scutes, and the abundance of prey items in the benthic environment. They do, however, still share several primitive characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements, and unique jaw suspension. Phylogeny and taxonomy
Despite the existence of a fossil record, full classification and phylogeny of the sturgeon species has been difficult to determine, in part due to the high individual and ontogenic variation, including geographical clines in certain features, such as rostrum shape, number of scutes, and body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. While ray finned fishes (Actinopterygii) have a long evolutionary history culminating in the most familiar fishes, past adaptive evolutionary radiations have left only a few survivors, such as sturgeons and gars. The wide range of the acipenserids and their endangered status have made collection of systematic materials difficult. The factors have led researchers in the past to identify over 40 additional species that were rejected by later scientists. Whether the species in the Acipenser and Huso genera are monophyletic (descended from one ancestor) or paraphyletic (descended from many ancestors) is still unclear, though the morphologically motivated division between these two genera clearly is not supported by the genetic evidence. An effort is ongoing to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques. The phylogeny of Acipenseridae, as in the cladogram, shows that they evolved from the bony fishes. Approximate dates are from Near et al., 2012. However, multiple recent studies have recovered this arrangement as paraphyletic, instead finding A. oxyrhinchus and A. sturio to form the most basal clade among sturgeons, and all other species being in a separate clade, with the various other species of Acipenser, Scaphirhynchus, Pseudoscaphirhynchus, and Huso to have varying levels of relationship with one another. A potential taxonomy of Acipenseridae is shown here, based on Luo et al. 2019, Nedoluzhko et al. 2020, and Shen et al. 2020. Note the paraphyletic relationships among genera:
The exact placement of Scaphirhynchus varies depending on the study and the methods used, with some placing it within the second most basal clade comprising primarily Pacific species (shown above), whereas others place it in its own clade that is more derived than the secondmost basal clade but less derived than the most derived Atlantic and Central Asian clade. No studies have yet delineated a relationship between it and Pseudoscaphirhynchus. In addition, the exact relationships of the members of the most derived, primarily Atlantic clade vary, although most analyses at least find all the species in it to form a monophyletic clade. The placement of A. sinensis also varies by the study, with some placing it as the only Pacific member of the otherwise Atlantic based most derived clade, whereas others place it with the rest of the Pacific sturgeons as a sister to A. dabryanus. in the rivers that flow into the Black, Azov, and Caspian Seas (Danube, Dnepr, Volga, Ural and Don); the north flowing rivers of Russia that feed the Arctic Ocean (Ob, Yenisei, Lena, Kolyma); in the rivers of Central Asia (Amu Darya and Syr Darya) and Lake Baikal. In the Pacific Ocean, they are found in the Amur River along the Russian Chinese border, on Sakhalin Island, and some rivers in northeast China. Most species are at least partially anadromous, spawning in fresh water and feeding in nutrient rich, brackish waters of estuaries or undergoing significant migrations along coastlines. However, some species have evolved purely freshwater existences, such as the lake sturgeon (Acipenser fulvescens) and the Baikal sturgeon (A. baerii baicalensis), or have been forced into them by human or natural impoundment of their native rivers, as in the case of some subpopulations of white sturgeon (A. transmontanus) in the Columbia River and Siberian sturgeon (A. baerii) in the Ob basin. Physical characteristics
Sturgeons retain several primitive characteristics from the bony fishes. Along with other members of the subclass Chondrostei, they are unique among bony fishes because their skeletons are almost entirely cartilaginous. To maintain structure, sturgeons are one of few organisms to retain a post embryonic notochord that acts like a soft spine running through the body. Notably, however, the cartilagineous skeleton is not a primitive character, but a derived one; sturgeon ancestors had bony skeletons. They also lack vertebral centra, and are partially covered with five lateral rows of scutes rather than scales. They also have four barbels—sensory organs that precede their wide, toothless mouths. They navigate their riverine habitats traveling just off the bottom with their barbels dragging along gravel, or murky substrate. Sturgeon are recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes. The skeletal support for the paired fins of ray finned fish is inside the body wall, although the ray like structures in the webbing of the fins can be seen externally. Sturgeons are among the largest fish: some beluga (Huso huso) in the Caspian Sea reportedly attain over and while for kaluga (H. dauricus) in the Amur River, similar lengths and over weights have been reported. They are also among the longest lived of the fishes, some living well over 100 years and attaining sexual maturity at 20 years or more. The combination of slow growth and reproductive rates and the extremely high value placed on mature, egg bearing females make sturgeon particularly vulnerable to overfishing. Sturgeons are polyploid; some species have four, eight, or 16 sets of chromosomes. Life cycle
Sturgeons are long lived, late maturing fishes. Their average lifespan is 50 to 60 years, and their first spawn does not occur until they are around 15 to 20 years old. Sturgeons are broadcast spawners, and do not spawn every year because they require specific conditions. Those requirements may or may not be met every year due to varying environmental conditions, such as the proper photoperiod in spring, clear water with shallow rock or gravel substrate, where the eggs can adhere, and proper water temperature and flow for oxygenation of the eggs. A single female may release 100,000 to 3 million eggs, but not all will be fertilized. The fertilized eggs become sticky and adhere to the bottom substrate upon contact. Eight to 15 days are needed for the embryos to mature into larval fish. During that time, they are dependent on their yolk sacs for nourishment. River currents carry the larvae downstream into backwater areas, such as oxbows and sloughs, where the free swimming fry spend their first year feeding on insect larvae and crustacea. During their first year of growth, they reach in length and migrate back into the swift flowing currents in the main stem river. Behavior
Sturgeons are primarily benthic feeders, with a diet of shellfish, crustaceans, and small fish. Exceptionally, both Huso'' species, the white sturgeon and the pallid sturgeon feed primarily on other fish as adults. They feed by extending their siphon like mouths to suck food from the benthos. Having no teeth, they are unable to seize prey, though larger individuals and more predatory species can swallow very large prey items, including whole salmon. Sturgeons feed non visually. They are believed to use a combination of sensors, including olfactory, tactile, and chemosensory cues detected by the four barbels, and electroreception using their ampullae of Lorenzini. The electroreceptors are thought to be used in various behaviors such as feeding, mating and migration. Many sturgeons leap completely out of the water, usually making a loud splash which can be heard half a mile away on the surface and probably further under water. Why they do this is not known, but suggested functions include group communication to maintain group cohesion, catching airborne prey, courtship display, or to help shed eggs during spawning. Other plausible explanations include escape from predators, shedding parasites, or to gulp or expel air. Another explanation is that it "simply feels good". in 2015, a 5 year old girl was fatally injured after a sturgeon leapt from the Suwannee River and struck her.
Аципенсериформные рыбы появились в летописи окаменелостей примерно 174–201 миллион лет назад, в раннем юрском периоде, что делает их одними из самых ранних сохранившихся лучепёрых рыб. Истинные осетры появляются в летописи окаменелостей в верхнем меловом периоде, среди самых старых известных останков — частичный череп из ценоманского периода (100–94 миллиона лет назад) из Альберты, Канада. За это время осетры претерпели удивительно мало морфологических изменений, что указывает на исключительно медленную эволюцию и заслужило им неофициальный статус «живых ископаемых». Это частично объясняется длительным периодом генерации, толерантностью к широкому диапазону температур и солёности, отсутствием хищников из-за размера и костного панциря (щитков), а также обилием добычи в бентосной среде. Однако они всё ещё сохраняют несколько примитивных характеристик, таких как гетероцеркальный хвост, редуцированная чешуя, больше плавников, чем поддерживающих костных элементов, и уникальная структура челюстного подвеса.
Ray finned fish
Automatic taxobox
| name = Sturgeon
| image = Acipenser oxyrhynchus (edit). png
| image caption = Atlantic sturgeon(Acipenser oxyrinchus oxyrinchus)
| fossil range =
| taxon = Acipenseridae
| authority = Bonaparte, 1831
| subdivision ranks = Genera
| subdivision =
†Boreiosturion
†Protoscaphirhynchus
†Engdahlichthys
†Anchiacipenser
†Priscosturion
Acipenser (paraphyletic)
Huso
ScaphirhynchusPseudoscaphirhynchus
Sturgeon (from Old English styrġa ultimately from Proto Indo European *str̥(Hx)yón ) is the common name for the 28 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early Jurassic period, some 174 to 201 million years ago. They are one of two living families of the Acipenseriformes alongside paddlefish (Polyodontidae). The family is grouped into four genera: Acipenser (which is paraphyletic, containing many distantly related sturgeon species), Huso, Scaphirhynchus, and Pseudoscaphirhynchus. Two species (A. naccarii and A. dabryanus) may be extinct in the wild, and one (P. fedtschenkoi) may be entirely extinct. Sturgeons are native to subtropical, temperate and sub Arctic rivers, lakes and coastlines of Eurasia and North America. A Maastrichtian age fossil found in Morocco shows that they also once lived in Africa. Sturgeons are long lived, late maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle like body that is smooth skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging in length. The largest sturgeon on record was a beluga female captured in the Volga Delta in 1827, measuring long and weighing Most sturgeons are anadromous bottom feeders, migrating upstream to spawn but spending most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. Several species of sturgeon are harvested for their roe, which is processed into the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction. Evolution
Fossil history
Acipenseriform fishes appeared in the fossil record some 174 to 201 million years ago, during the Early Jurassic, making them some of the earliest extant actinopterygian fishes. True sturgeons appear in the fossil record during the Upper Cretaceous, with amongst the oldest known remains being a partial skull from the Cenomanian (100–94 million years ago) of Alberta, Canada. In that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils. This is explained in part by the long generation interval, tolerance for wide ranges of temperature and salinity, lack of predators due to size and bony plated armor, or scutes, and the abundance of prey items in the benthic environment. They do, however, still share several primitive characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements, and unique jaw suspension. Phylogeny and taxonomy
Despite the existence of a fossil record, full classification and phylogeny of the sturgeon species has been difficult to determine, in part due to the high individual and ontogenic variation, including geographical clines in certain features, such as rostrum shape, number of scutes, and body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. While ray finned fishes (Actinopterygii) have a long evolutionary history culminating in the most familiar fishes, past adaptive evolutionary radiations have left only a few survivors, such as sturgeons and gars. The wide range of the acipenserids and their endangered status have made collection of systematic materials difficult. The factors have led researchers in the past to identify over 40 additional species that were rejected by later scientists. Whether the species in the Acipenser and Huso genera are monophyletic (descended from one ancestor) or paraphyletic (descended from many ancestors) is still unclear, though the morphologically motivated division between these two genera clearly is not supported by the genetic evidence. An effort is ongoing to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques. The phylogeny of Acipenseridae, as in the cladogram, shows that they evolved from the bony fishes. Approximate dates are from Near et al., 2012. However, multiple recent studies have recovered this arrangement as paraphyletic, instead finding A. oxyrhinchus and A. sturio to form the most basal clade among sturgeons, and all other species being in a separate clade, with the various other species of Acipenser, Scaphirhynchus, Pseudoscaphirhynchus, and Huso to have varying levels of relationship with one another. A potential taxonomy of Acipenseridae is shown here, based on Luo et al. 2019, Nedoluzhko et al. 2020, and Shen et al. 2020. Note the paraphyletic relationships among genera:
The exact placement of Scaphirhynchus varies depending on the study and the methods used, with some placing it within the second most basal clade comprising primarily Pacific species (shown above), whereas others place it in its own clade that is more derived than the secondmost basal clade but less derived than the most derived Atlantic and Central Asian clade. No studies have yet delineated a relationship between it and Pseudoscaphirhynchus. In addition, the exact relationships of the members of the most derived, primarily Atlantic clade vary, although most analyses at least find all the species in it to form a monophyletic clade. The placement of A. sinensis also varies by the study, with some placing it as the only Pacific member of the otherwise Atlantic based most derived clade, whereas others place it with the rest of the Pacific sturgeons as a sister to A. dabryanus. in the rivers that flow into the Black, Azov, and Caspian Seas (Danube, Dnepr, Volga, Ural and Don); the north flowing rivers of Russia that feed the Arctic Ocean (Ob, Yenisei, Lena, Kolyma); in the rivers of Central Asia (Amu Darya and Syr Darya) and Lake Baikal. In the Pacific Ocean, they are found in the Amur River along the Russian Chinese border, on Sakhalin Island, and some rivers in northeast China. Most species are at least partially anadromous, spawning in fresh water and feeding in nutrient rich, brackish waters of estuaries or undergoing significant migrations along coastlines. However, some species have evolved purely freshwater existences, such as the lake sturgeon (Acipenser fulvescens) and the Baikal sturgeon (A. baerii baicalensis), or have been forced into them by human or natural impoundment of their native rivers, as in the case of some subpopulations of white sturgeon (A. transmontanus) in the Columbia River and Siberian sturgeon (A. baerii) in the Ob basin. Physical characteristics
Sturgeons retain several primitive characteristics from the bony fishes. Along with other members of the subclass Chondrostei, they are unique among bony fishes because their skeletons are almost entirely cartilaginous. To maintain structure, sturgeons are one of few organisms to retain a post embryonic notochord that acts like a soft spine running through the body. Notably, however, the cartilagineous skeleton is not a primitive character, but a derived one; sturgeon ancestors had bony skeletons. They also lack vertebral centra, and are partially covered with five lateral rows of scutes rather than scales. They also have four barbels—sensory organs that precede their wide, toothless mouths. They navigate their riverine habitats traveling just off the bottom with their barbels dragging along gravel, or murky substrate. Sturgeon are recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes. The skeletal support for the paired fins of ray finned fish is inside the body wall, although the ray like structures in the webbing of the fins can be seen externally. Sturgeons are among the largest fish: some beluga (Huso huso) in the Caspian Sea reportedly attain over and while for kaluga (H. dauricus) in the Amur River, similar lengths and over weights have been reported. They are also among the longest lived of the fishes, some living well over 100 years and attaining sexual maturity at 20 years or more. The combination of slow growth and reproductive rates and the extremely high value placed on mature, egg bearing females make sturgeon particularly vulnerable to overfishing. Sturgeons are polyploid; some species have four, eight, or 16 sets of chromosomes. Life cycle
Sturgeons are long lived, late maturing fishes. Their average lifespan is 50 to 60 years, and their first spawn does not occur until they are around 15 to 20 years old. Sturgeons are broadcast spawners, and do not spawn every year because they require specific conditions. Those requirements may or may not be met every year due to varying environmental conditions, such as the proper photoperiod in spring, clear water with shallow rock or gravel substrate, where the eggs can adhere, and proper water temperature and flow for oxygenation of the eggs. A single female may release 100,000 to 3 million eggs, but not all will be fertilized. The fertilized eggs become sticky and adhere to the bottom substrate upon contact. Eight to 15 days are needed for the embryos to mature into larval fish. During that time, they are dependent on their yolk sacs for nourishment. River currents carry the larvae downstream into backwater areas, such as oxbows and sloughs, where the free swimming fry spend their first year feeding on insect larvae and crustacea. During their first year of growth, they reach in length and migrate back into the swift flowing currents in the main stem river. Behavior
Sturgeons are primarily benthic feeders, with a diet of shellfish, crustaceans, and small fish. Exceptionally, both Huso'' species, the white sturgeon and the pallid sturgeon feed primarily on other fish as adults. They feed by extending their siphon like mouths to suck food from the benthos. Having no teeth, they are unable to seize prey, though larger individuals and more predatory species can swallow very large prey items, including whole salmon. Sturgeons feed non visually. They are believed to use a combination of sensors, including olfactory, tactile, and chemosensory cues detected by the four barbels, and electroreception using their ampullae of Lorenzini. The electroreceptors are thought to be used in various behaviors such as feeding, mating and migration. Many sturgeons leap completely out of the water, usually making a loud splash which can be heard half a mile away on the surface and probably further under water. Why they do this is not known, but suggested functions include group communication to maintain group cohesion, catching airborne prey, courtship display, or to help shed eggs during spawning. Other plausible explanations include escape from predators, shedding parasites, or to gulp or expel air. Another explanation is that it "simply feels good". in 2015, a 5 year old girl was fatally injured after a sturgeon leapt from the Suwannee River and struck her.
Automatic taxobox
| name = Sturgeon
| image = Acipenser oxyrhynchus (edit). png
| image caption = Atlantic sturgeon(Acipenser oxyrinchus oxyrinchus)
| fossil range =
| taxon = Acipenseridae
| authority = Bonaparte, 1831
| subdivision ranks = Genera
| subdivision =
†Boreiosturion
†Protoscaphirhynchus
†Engdahlichthys
†Anchiacipenser
†Priscosturion
Acipenser (paraphyletic)
Huso
ScaphirhynchusPseudoscaphirhynchus
Sturgeon (from Old English styrġa ultimately from Proto Indo European *str̥(Hx)yón ) is the common name for the 28 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early Jurassic period, some 174 to 201 million years ago. They are one of two living families of the Acipenseriformes alongside paddlefish (Polyodontidae). The family is grouped into four genera: Acipenser (which is paraphyletic, containing many distantly related sturgeon species), Huso, Scaphirhynchus, and Pseudoscaphirhynchus. Two species (A. naccarii and A. dabryanus) may be extinct in the wild, and one (P. fedtschenkoi) may be entirely extinct. Sturgeons are native to subtropical, temperate and sub Arctic rivers, lakes and coastlines of Eurasia and North America. A Maastrichtian age fossil found in Morocco shows that they also once lived in Africa. Sturgeons are long lived, late maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle like body that is smooth skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging in length. The largest sturgeon on record was a beluga female captured in the Volga Delta in 1827, measuring long and weighing Most sturgeons are anadromous bottom feeders, migrating upstream to spawn but spending most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. Several species of sturgeon are harvested for their roe, which is processed into the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction. Evolution
Fossil history
Acipenseriform fishes appeared in the fossil record some 174 to 201 million years ago, during the Early Jurassic, making them some of the earliest extant actinopterygian fishes. True sturgeons appear in the fossil record during the Upper Cretaceous, with amongst the oldest known remains being a partial skull from the Cenomanian (100–94 million years ago) of Alberta, Canada. In that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils. This is explained in part by the long generation interval, tolerance for wide ranges of temperature and salinity, lack of predators due to size and bony plated armor, or scutes, and the abundance of prey items in the benthic environment. They do, however, still share several primitive characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements, and unique jaw suspension. Phylogeny and taxonomy
Despite the existence of a fossil record, full classification and phylogeny of the sturgeon species has been difficult to determine, in part due to the high individual and ontogenic variation, including geographical clines in certain features, such as rostrum shape, number of scutes, and body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. While ray finned fishes (Actinopterygii) have a long evolutionary history culminating in the most familiar fishes, past adaptive evolutionary radiations have left only a few survivors, such as sturgeons and gars. The wide range of the acipenserids and their endangered status have made collection of systematic materials difficult. The factors have led researchers in the past to identify over 40 additional species that were rejected by later scientists. Whether the species in the Acipenser and Huso genera are monophyletic (descended from one ancestor) or paraphyletic (descended from many ancestors) is still unclear, though the morphologically motivated division between these two genera clearly is not supported by the genetic evidence. An effort is ongoing to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques. The phylogeny of Acipenseridae, as in the cladogram, shows that they evolved from the bony fishes. Approximate dates are from Near et al., 2012. However, multiple recent studies have recovered this arrangement as paraphyletic, instead finding A. oxyrhinchus and A. sturio to form the most basal clade among sturgeons, and all other species being in a separate clade, with the various other species of Acipenser, Scaphirhynchus, Pseudoscaphirhynchus, and Huso to have varying levels of relationship with one another. A potential taxonomy of Acipenseridae is shown here, based on Luo et al. 2019, Nedoluzhko et al. 2020, and Shen et al. 2020. Note the paraphyletic relationships among genera:
The exact placement of Scaphirhynchus varies depending on the study and the methods used, with some placing it within the second most basal clade comprising primarily Pacific species (shown above), whereas others place it in its own clade that is more derived than the secondmost basal clade but less derived than the most derived Atlantic and Central Asian clade. No studies have yet delineated a relationship between it and Pseudoscaphirhynchus. In addition, the exact relationships of the members of the most derived, primarily Atlantic clade vary, although most analyses at least find all the species in it to form a monophyletic clade. The placement of A. sinensis also varies by the study, with some placing it as the only Pacific member of the otherwise Atlantic based most derived clade, whereas others place it with the rest of the Pacific sturgeons as a sister to A. dabryanus. in the rivers that flow into the Black, Azov, and Caspian Seas (Danube, Dnepr, Volga, Ural and Don); the north flowing rivers of Russia that feed the Arctic Ocean (Ob, Yenisei, Lena, Kolyma); in the rivers of Central Asia (Amu Darya and Syr Darya) and Lake Baikal. In the Pacific Ocean, they are found in the Amur River along the Russian Chinese border, on Sakhalin Island, and some rivers in northeast China. Most species are at least partially anadromous, spawning in fresh water and feeding in nutrient rich, brackish waters of estuaries or undergoing significant migrations along coastlines. However, some species have evolved purely freshwater existences, such as the lake sturgeon (Acipenser fulvescens) and the Baikal sturgeon (A. baerii baicalensis), or have been forced into them by human or natural impoundment of their native rivers, as in the case of some subpopulations of white sturgeon (A. transmontanus) in the Columbia River and Siberian sturgeon (A. baerii) in the Ob basin. Physical characteristics
Sturgeons retain several primitive characteristics from the bony fishes. Along with other members of the subclass Chondrostei, they are unique among bony fishes because their skeletons are almost entirely cartilaginous. To maintain structure, sturgeons are one of few organisms to retain a post embryonic notochord that acts like a soft spine running through the body. Notably, however, the cartilagineous skeleton is not a primitive character, but a derived one; sturgeon ancestors had bony skeletons. They also lack vertebral centra, and are partially covered with five lateral rows of scutes rather than scales. They also have four barbels—sensory organs that precede their wide, toothless mouths. They navigate their riverine habitats traveling just off the bottom with their barbels dragging along gravel, or murky substrate. Sturgeon are recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes. The skeletal support for the paired fins of ray finned fish is inside the body wall, although the ray like structures in the webbing of the fins can be seen externally. Sturgeons are among the largest fish: some beluga (Huso huso) in the Caspian Sea reportedly attain over and while for kaluga (H. dauricus) in the Amur River, similar lengths and over weights have been reported. They are also among the longest lived of the fishes, some living well over 100 years and attaining sexual maturity at 20 years or more. The combination of slow growth and reproductive rates and the extremely high value placed on mature, egg bearing females make sturgeon particularly vulnerable to overfishing. Sturgeons are polyploid; some species have four, eight, or 16 sets of chromosomes. Life cycle
Sturgeons are long lived, late maturing fishes. Their average lifespan is 50 to 60 years, and their first spawn does not occur until they are around 15 to 20 years old. Sturgeons are broadcast spawners, and do not spawn every year because they require specific conditions. Those requirements may or may not be met every year due to varying environmental conditions, such as the proper photoperiod in spring, clear water with shallow rock or gravel substrate, where the eggs can adhere, and proper water temperature and flow for oxygenation of the eggs. A single female may release 100,000 to 3 million eggs, but not all will be fertilized. The fertilized eggs become sticky and adhere to the bottom substrate upon contact. Eight to 15 days are needed for the embryos to mature into larval fish. During that time, they are dependent on their yolk sacs for nourishment. River currents carry the larvae downstream into backwater areas, such as oxbows and sloughs, where the free swimming fry spend their first year feeding on insect larvae and crustacea. During their first year of growth, they reach in length and migrate back into the swift flowing currents in the main stem river. Behavior
Sturgeons are primarily benthic feeders, with a diet of shellfish, crustaceans, and small fish. Exceptionally, both Huso'' species, the white sturgeon and the pallid sturgeon feed primarily on other fish as adults. They feed by extending their siphon like mouths to suck food from the benthos. Having no teeth, they are unable to seize prey, though larger individuals and more predatory species can swallow very large prey items, including whole salmon. Sturgeons feed non visually. They are believed to use a combination of sensors, including olfactory, tactile, and chemosensory cues detected by the four barbels, and electroreception using their ampullae of Lorenzini. The electroreceptors are thought to be used in various behaviors such as feeding, mating and migration. Many sturgeons leap completely out of the water, usually making a loud splash which can be heard half a mile away on the surface and probably further under water. Why they do this is not known, but suggested functions include group communication to maintain group cohesion, catching airborne prey, courtship display, or to help shed eggs during spawning. Other plausible explanations include escape from predators, shedding parasites, or to gulp or expel air. Another explanation is that it "simply feels good". in 2015, a 5 year old girl was fatally injured after a sturgeon leapt from the Suwannee River and struck her.
Филогения и таксономия
Ray finned fish
Automatic taxobox
| name = Sturgeon
| image = Acipenser oxyrhynchus (edit). png
| image caption = Atlantic sturgeon(Acipenser oxyrinchus oxyrinchus)
| fossil range =
| taxon = Acipenseridae
| authority = Bonaparte, 1831
| subdivision ranks = Genera
| subdivision =
†Boreiosturion
†Protoscaphirhynchus
†Engdahlichthys
†Anchiacipenser
†Priscosturion
Acipenser (paraphyletic)
Huso
ScaphirhynchusPseudoscaphirhynchus
Sturgeon (from Old English styrġa ultimately from Proto Indo European *str̥(Hx)yón ) is the common name for the 28 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early Jurassic period, some 174 to 201 million years ago. They are one of two living families of the Acipenseriformes alongside paddlefish (Polyodontidae). The family is grouped into four genera: Acipenser (which is paraphyletic, containing many distantly related sturgeon species), Huso, Scaphirhynchus, and Pseudoscaphirhynchus. Two species (A. naccarii and A. dabryanus) may be extinct in the wild, and one (P. fedtschenkoi) may be entirely extinct. Sturgeons are native to subtropical, temperate and sub Arctic rivers, lakes and coastlines of Eurasia and North America. A Maastrichtian age fossil found in Morocco shows that they also once lived in Africa. Sturgeons are long lived, late maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle like body that is smooth skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging in length. The largest sturgeon on record was a beluga female captured in the Volga Delta in 1827, measuring long and weighing Most sturgeons are anadromous bottom feeders, migrating upstream to spawn but spending most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. Several species of sturgeon are harvested for their roe, which is processed into the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction. Evolution
Fossil history
Acipenseriform fishes appeared in the fossil record some 174 to 201 million years ago, during the Early Jurassic, making them some of the earliest extant actinopterygian fishes. True sturgeons appear in the fossil record during the Upper Cretaceous, with amongst the oldest known remains being a partial skull from the Cenomanian (100–94 million years ago) of Alberta, Canada. In that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils. This is explained in part by the long generation interval, tolerance for wide ranges of temperature and salinity, lack of predators due to size and bony plated armor, or scutes, and the abundance of prey items in the benthic environment. They do, however, still share several primitive characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements, and unique jaw suspension. Phylogeny and taxonomy
Despite the existence of a fossil record, full classification and phylogeny of the sturgeon species has been difficult to determine, in part due to the high individual and ontogenic variation, including geographical clines in certain features, such as rostrum shape, number of scutes, and body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. While ray finned fishes (Actinopterygii) have a long evolutionary history culminating in the most familiar fishes, past adaptive evolutionary radiations have left only a few survivors, such as sturgeons and gars. The wide range of the acipenserids and their endangered status have made collection of systematic materials difficult. The factors have led researchers in the past to identify over 40 additional species that were rejected by later scientists. Whether the species in the Acipenser and Huso genera are monophyletic (descended from one ancestor) or paraphyletic (descended from many ancestors) is still unclear, though the morphologically motivated division between these two genera clearly is not supported by the genetic evidence. An effort is ongoing to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques. The phylogeny of Acipenseridae, as in the cladogram, shows that they evolved from the bony fishes. Approximate dates are from Near et al., 2012. However, multiple recent studies have recovered this arrangement as paraphyletic, instead finding A. oxyrhinchus and A. sturio to form the most basal clade among sturgeons, and all other species being in a separate clade, with the various other species of Acipenser, Scaphirhynchus, Pseudoscaphirhynchus, and Huso to have varying levels of relationship with one another. A potential taxonomy of Acipenseridae is shown here, based on Luo et al. 2019, Nedoluzhko et al. 2020, and Shen et al. 2020. Note the paraphyletic relationships among genera:
The exact placement of Scaphirhynchus varies depending on the study and the methods used, with some placing it within the second most basal clade comprising primarily Pacific species (shown above), whereas others place it in its own clade that is more derived than the secondmost basal clade but less derived than the most derived Atlantic and Central Asian clade. No studies have yet delineated a relationship between it and Pseudoscaphirhynchus. In addition, the exact relationships of the members of the most derived, primarily Atlantic clade vary, although most analyses at least find all the species in it to form a monophyletic clade. The placement of A. sinensis also varies by the study, with some placing it as the only Pacific member of the otherwise Atlantic based most derived clade, whereas others place it with the rest of the Pacific sturgeons as a sister to A. dabryanus. in the rivers that flow into the Black, Azov, and Caspian Seas (Danube, Dnepr, Volga, Ural and Don); the north flowing rivers of Russia that feed the Arctic Ocean (Ob, Yenisei, Lena, Kolyma); in the rivers of Central Asia (Amu Darya and Syr Darya) and Lake Baikal. In the Pacific Ocean, they are found in the Amur River along the Russian Chinese border, on Sakhalin Island, and some rivers in northeast China. Most species are at least partially anadromous, spawning in fresh water and feeding in nutrient rich, brackish waters of estuaries or undergoing significant migrations along coastlines. However, some species have evolved purely freshwater existences, such as the lake sturgeon (Acipenser fulvescens) and the Baikal sturgeon (A. baerii baicalensis), or have been forced into them by human or natural impoundment of their native rivers, as in the case of some subpopulations of white sturgeon (A. transmontanus) in the Columbia River and Siberian sturgeon (A. baerii) in the Ob basin. Physical characteristics
Sturgeons retain several primitive characteristics from the bony fishes. Along with other members of the subclass Chondrostei, they are unique among bony fishes because their skeletons are almost entirely cartilaginous. To maintain structure, sturgeons are one of few organisms to retain a post embryonic notochord that acts like a soft spine running through the body. Notably, however, the cartilagineous skeleton is not a primitive character, but a derived one; sturgeon ancestors had bony skeletons. They also lack vertebral centra, and are partially covered with five lateral rows of scutes rather than scales. They also have four barbels—sensory organs that precede their wide, toothless mouths. They navigate their riverine habitats traveling just off the bottom with their barbels dragging along gravel, or murky substrate. Sturgeon are recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes. The skeletal support for the paired fins of ray finned fish is inside the body wall, although the ray like structures in the webbing of the fins can be seen externally. Sturgeons are among the largest fish: some beluga (Huso huso) in the Caspian Sea reportedly attain over and while for kaluga (H. dauricus) in the Amur River, similar lengths and over weights have been reported. They are also among the longest lived of the fishes, some living well over 100 years and attaining sexual maturity at 20 years or more. The combination of slow growth and reproductive rates and the extremely high value placed on mature, egg bearing females make sturgeon particularly vulnerable to overfishing. Sturgeons are polyploid; some species have four, eight, or 16 sets of chromosomes. Life cycle
Sturgeons are long lived, late maturing fishes. Their average lifespan is 50 to 60 years, and their first spawn does not occur until they are around 15 to 20 years old. Sturgeons are broadcast spawners, and do not spawn every year because they require specific conditions. Those requirements may or may not be met every year due to varying environmental conditions, such as the proper photoperiod in spring, clear water with shallow rock or gravel substrate, where the eggs can adhere, and proper water temperature and flow for oxygenation of the eggs. A single female may release 100,000 to 3 million eggs, but not all will be fertilized. The fertilized eggs become sticky and adhere to the bottom substrate upon contact. Eight to 15 days are needed for the embryos to mature into larval fish. During that time, they are dependent on their yolk sacs for nourishment. River currents carry the larvae downstream into backwater areas, such as oxbows and sloughs, where the free swimming fry spend their first year feeding on insect larvae and crustacea. During their first year of growth, they reach in length and migrate back into the swift flowing currents in the main stem river. Behavior
Sturgeons are primarily benthic feeders, with a diet of shellfish, crustaceans, and small fish. Exceptionally, both Huso'' species, the white sturgeon and the pallid sturgeon feed primarily on other fish as adults. They feed by extending their siphon like mouths to suck food from the benthos. Having no teeth, they are unable to seize prey, though larger individuals and more predatory species can swallow very large prey items, including whole salmon. Sturgeons feed non visually. They are believed to use a combination of sensors, including olfactory, tactile, and chemosensory cues detected by the four barbels, and electroreception using their ampullae of Lorenzini. The electroreceptors are thought to be used in various behaviors such as feeding, mating and migration. Many sturgeons leap completely out of the water, usually making a loud splash which can be heard half a mile away on the surface and probably further under water. Why they do this is not known, but suggested functions include group communication to maintain group cohesion, catching airborne prey, courtship display, or to help shed eggs during spawning. Other plausible explanations include escape from predators, shedding parasites, or to gulp or expel air. Another explanation is that it "simply feels good". in 2015, a 5 year old girl was fatally injured after a sturgeon leapt from the Suwannee River and struck her.
Automatic taxobox
| name = Sturgeon
| image = Acipenser oxyrhynchus (edit). png
| image caption = Atlantic sturgeon(Acipenser oxyrinchus oxyrinchus)
| fossil range =
| taxon = Acipenseridae
| authority = Bonaparte, 1831
| subdivision ranks = Genera
| subdivision =
†Boreiosturion
†Protoscaphirhynchus
†Engdahlichthys
†Anchiacipenser
†Priscosturion
Acipenser (paraphyletic)
Huso
ScaphirhynchusPseudoscaphirhynchus
Sturgeon (from Old English styrġa ultimately from Proto Indo European *str̥(Hx)yón ) is the common name for the 28 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early Jurassic period, some 174 to 201 million years ago. They are one of two living families of the Acipenseriformes alongside paddlefish (Polyodontidae). The family is grouped into four genera: Acipenser (which is paraphyletic, containing many distantly related sturgeon species), Huso, Scaphirhynchus, and Pseudoscaphirhynchus. Two species (A. naccarii and A. dabryanus) may be extinct in the wild, and one (P. fedtschenkoi) may be entirely extinct. Sturgeons are native to subtropical, temperate and sub Arctic rivers, lakes and coastlines of Eurasia and North America. A Maastrichtian age fossil found in Morocco shows that they also once lived in Africa. Sturgeons are long lived, late maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle like body that is smooth skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging in length. The largest sturgeon on record was a beluga female captured in the Volga Delta in 1827, measuring long and weighing Most sturgeons are anadromous bottom feeders, migrating upstream to spawn but spending most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. Several species of sturgeon are harvested for their roe, which is processed into the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction. Evolution
Fossil history
Acipenseriform fishes appeared in the fossil record some 174 to 201 million years ago, during the Early Jurassic, making them some of the earliest extant actinopterygian fishes. True sturgeons appear in the fossil record during the Upper Cretaceous, with amongst the oldest known remains being a partial skull from the Cenomanian (100–94 million years ago) of Alberta, Canada. In that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils. This is explained in part by the long generation interval, tolerance for wide ranges of temperature and salinity, lack of predators due to size and bony plated armor, or scutes, and the abundance of prey items in the benthic environment. They do, however, still share several primitive characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements, and unique jaw suspension. Phylogeny and taxonomy
Despite the existence of a fossil record, full classification and phylogeny of the sturgeon species has been difficult to determine, in part due to the high individual and ontogenic variation, including geographical clines in certain features, such as rostrum shape, number of scutes, and body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. While ray finned fishes (Actinopterygii) have a long evolutionary history culminating in the most familiar fishes, past adaptive evolutionary radiations have left only a few survivors, such as sturgeons and gars. The wide range of the acipenserids and their endangered status have made collection of systematic materials difficult. The factors have led researchers in the past to identify over 40 additional species that were rejected by later scientists. Whether the species in the Acipenser and Huso genera are monophyletic (descended from one ancestor) or paraphyletic (descended from many ancestors) is still unclear, though the morphologically motivated division between these two genera clearly is not supported by the genetic evidence. An effort is ongoing to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques. The phylogeny of Acipenseridae, as in the cladogram, shows that they evolved from the bony fishes. Approximate dates are from Near et al., 2012. However, multiple recent studies have recovered this arrangement as paraphyletic, instead finding A. oxyrhinchus and A. sturio to form the most basal clade among sturgeons, and all other species being in a separate clade, with the various other species of Acipenser, Scaphirhynchus, Pseudoscaphirhynchus, and Huso to have varying levels of relationship with one another. A potential taxonomy of Acipenseridae is shown here, based on Luo et al. 2019, Nedoluzhko et al. 2020, and Shen et al. 2020. Note the paraphyletic relationships among genera:
The exact placement of Scaphirhynchus varies depending on the study and the methods used, with some placing it within the second most basal clade comprising primarily Pacific species (shown above), whereas others place it in its own clade that is more derived than the secondmost basal clade but less derived than the most derived Atlantic and Central Asian clade. No studies have yet delineated a relationship between it and Pseudoscaphirhynchus. In addition, the exact relationships of the members of the most derived, primarily Atlantic clade vary, although most analyses at least find all the species in it to form a monophyletic clade. The placement of A. sinensis also varies by the study, with some placing it as the only Pacific member of the otherwise Atlantic based most derived clade, whereas others place it with the rest of the Pacific sturgeons as a sister to A. dabryanus. in the rivers that flow into the Black, Azov, and Caspian Seas (Danube, Dnepr, Volga, Ural and Don); the north flowing rivers of Russia that feed the Arctic Ocean (Ob, Yenisei, Lena, Kolyma); in the rivers of Central Asia (Amu Darya and Syr Darya) and Lake Baikal. In the Pacific Ocean, they are found in the Amur River along the Russian Chinese border, on Sakhalin Island, and some rivers in northeast China. Most species are at least partially anadromous, spawning in fresh water and feeding in nutrient rich, brackish waters of estuaries or undergoing significant migrations along coastlines. However, some species have evolved purely freshwater existences, such as the lake sturgeon (Acipenser fulvescens) and the Baikal sturgeon (A. baerii baicalensis), or have been forced into them by human or natural impoundment of their native rivers, as in the case of some subpopulations of white sturgeon (A. transmontanus) in the Columbia River and Siberian sturgeon (A. baerii) in the Ob basin. Physical characteristics
Sturgeons retain several primitive characteristics from the bony fishes. Along with other members of the subclass Chondrostei, they are unique among bony fishes because their skeletons are almost entirely cartilaginous. To maintain structure, sturgeons are one of few organisms to retain a post embryonic notochord that acts like a soft spine running through the body. Notably, however, the cartilagineous skeleton is not a primitive character, but a derived one; sturgeon ancestors had bony skeletons. They also lack vertebral centra, and are partially covered with five lateral rows of scutes rather than scales. They also have four barbels—sensory organs that precede their wide, toothless mouths. They navigate their riverine habitats traveling just off the bottom with their barbels dragging along gravel, or murky substrate. Sturgeon are recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes. The skeletal support for the paired fins of ray finned fish is inside the body wall, although the ray like structures in the webbing of the fins can be seen externally. Sturgeons are among the largest fish: some beluga (Huso huso) in the Caspian Sea reportedly attain over and while for kaluga (H. dauricus) in the Amur River, similar lengths and over weights have been reported. They are also among the longest lived of the fishes, some living well over 100 years and attaining sexual maturity at 20 years or more. The combination of slow growth and reproductive rates and the extremely high value placed on mature, egg bearing females make sturgeon particularly vulnerable to overfishing. Sturgeons are polyploid; some species have four, eight, or 16 sets of chromosomes. Life cycle
Sturgeons are long lived, late maturing fishes. Their average lifespan is 50 to 60 years, and their first spawn does not occur until they are around 15 to 20 years old. Sturgeons are broadcast spawners, and do not spawn every year because they require specific conditions. Those requirements may or may not be met every year due to varying environmental conditions, such as the proper photoperiod in spring, clear water with shallow rock or gravel substrate, where the eggs can adhere, and proper water temperature and flow for oxygenation of the eggs. A single female may release 100,000 to 3 million eggs, but not all will be fertilized. The fertilized eggs become sticky and adhere to the bottom substrate upon contact. Eight to 15 days are needed for the embryos to mature into larval fish. During that time, they are dependent on their yolk sacs for nourishment. River currents carry the larvae downstream into backwater areas, such as oxbows and sloughs, where the free swimming fry spend their first year feeding on insect larvae and crustacea. During their first year of growth, they reach in length and migrate back into the swift flowing currents in the main stem river. Behavior
Sturgeons are primarily benthic feeders, with a diet of shellfish, crustaceans, and small fish. Exceptionally, both Huso'' species, the white sturgeon and the pallid sturgeon feed primarily on other fish as adults. They feed by extending their siphon like mouths to suck food from the benthos. Having no teeth, they are unable to seize prey, though larger individuals and more predatory species can swallow very large prey items, including whole salmon. Sturgeons feed non visually. They are believed to use a combination of sensors, including olfactory, tactile, and chemosensory cues detected by the four barbels, and electroreception using their ampullae of Lorenzini. The electroreceptors are thought to be used in various behaviors such as feeding, mating and migration. Many sturgeons leap completely out of the water, usually making a loud splash which can be heard half a mile away on the surface and probably further under water. Why they do this is not known, but suggested functions include group communication to maintain group cohesion, catching airborne prey, courtship display, or to help shed eggs during spawning. Other plausible explanations include escape from predators, shedding parasites, or to gulp or expel air. Another explanation is that it "simply feels good". in 2015, a 5 year old girl was fatally injured after a sturgeon leapt from the Suwannee River and struck her.
Несмотря на наличие ископаемой летописи, полная классификация и филогения видов осетров оказалась сложной задачей, отчасти из-за высокой индивидуальной и онтогенетической изменчивости, включая географические градиенты в определенных признаках, таких как форма рыла, количество щитков и длина тела. Дополнительным фактором, усложняющим ситуацию, является уникальная способность осетров производить репродуктивно жизнеспособных гибридов, даже между видами, отнесёнными к разным родам. В то время как рыбы с лучевыми плавниками (Actinopterygii) имеют долгую эволюционную историю, кульминацией которой стали наиболее известные рыбы, прошлые адаптивные эволюционные радиации оставили лишь немногих выживших, таких как осетры и амиевые рыбы. Широкий ареал аципенсерид и их уязвимый статус затрудняют сбор систематических материалов. Эти факторы в прошлом привели к тому, что исследователи идентифицировали более 40 дополнительных видов, которые впоследствии были отвергнуты другими учёными. Остаётся неясным, являются ли виды в родах Acipenser и Huso монофилетическими (происходящими от одного предка) или парафилетическими (происходящими от нескольких предков), хотя морфологически обоснованное разделение между этими двумя родами явно не подтверждается генетическими данными. Предпринимаются усилия по разрешению таксономической путаницы посредством постоянного синтеза систематических данных и молекулярных методов. Филогения Acipenseridae, как показано на кладограмме, демонстрирует, что они эволюционировали от костных рыб. Приблизительные даты указаны Near et al., 2012. Однако многочисленные недавние исследования показали, что эта схема является парафилетической, вместо этого обнаруживая, что A. oxyrhinchus и A. sturio образуют наиболее базальную кладу среди осетров, а все остальные виды находятся в отдельной кладе, при этом различные другие виды Acipenser, Scaphirhynchus, Pseudoscaphirhynchus и Huso имеют различную степень родства друг с другом. Потенциальная таксономия Acipenseridae представлена здесь, основанная на Luo et al. 2019, Nedoluzhko et al. 2020 и Shen et al. 2020. Обратите внимание на парафилетические взаимосвязи между родами:
Ray finned fish
Automatic taxobox
| name = Sturgeon
| image = Acipenser oxyrhynchus (edit). png
| image caption = Atlantic sturgeon(Acipenser oxyrinchus oxyrinchus)
| fossil range =
| taxon = Acipenseridae
| authority = Bonaparte, 1831
| subdivision ranks = Genera
| subdivision =
†Boreiosturion
†Protoscaphirhynchus
†Engdahlichthys
†Anchiacipenser
†Priscosturion
Acipenser (paraphyletic)
Huso
ScaphirhynchusPseudoscaphirhynchus
Sturgeon (from Old English styrġa ultimately from Proto Indo European *str̥(Hx)yón ) is the common name for the 28 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early Jurassic period, some 174 to 201 million years ago. They are one of two living families of the Acipenseriformes alongside paddlefish (Polyodontidae). The family is grouped into four genera: Acipenser (which is paraphyletic, containing many distantly related sturgeon species), Huso, Scaphirhynchus, and Pseudoscaphirhynchus. Two species (A. naccarii and A. dabryanus) may be extinct in the wild, and one (P. fedtschenkoi) may be entirely extinct. Sturgeons are native to subtropical, temperate and sub Arctic rivers, lakes and coastlines of Eurasia and North America. A Maastrichtian age fossil found in Morocco shows that they also once lived in Africa. Sturgeons are long lived, late maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle like body that is smooth skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging in length. The largest sturgeon on record was a beluga female captured in the Volga Delta in 1827, measuring long and weighing Most sturgeons are anadromous bottom feeders, migrating upstream to spawn but spending most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. Several species of sturgeon are harvested for their roe, which is processed into the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction. Evolution
Fossil history
Acipenseriform fishes appeared in the fossil record some 174 to 201 million years ago, during the Early Jurassic, making them some of the earliest extant actinopterygian fishes. True sturgeons appear in the fossil record during the Upper Cretaceous, with amongst the oldest known remains being a partial skull from the Cenomanian (100–94 million years ago) of Alberta, Canada. In that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils. This is explained in part by the long generation interval, tolerance for wide ranges of temperature and salinity, lack of predators due to size and bony plated armor, or scutes, and the abundance of prey items in the benthic environment. They do, however, still share several primitive characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements, and unique jaw suspension. Phylogeny and taxonomy
Despite the existence of a fossil record, full classification and phylogeny of the sturgeon species has been difficult to determine, in part due to the high individual and ontogenic variation, including geographical clines in certain features, such as rostrum shape, number of scutes, and body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. While ray finned fishes (Actinopterygii) have a long evolutionary history culminating in the most familiar fishes, past adaptive evolutionary radiations have left only a few survivors, such as sturgeons and gars. The wide range of the acipenserids and their endangered status have made collection of systematic materials difficult. The factors have led researchers in the past to identify over 40 additional species that were rejected by later scientists. Whether the species in the Acipenser and Huso genera are monophyletic (descended from one ancestor) or paraphyletic (descended from many ancestors) is still unclear, though the morphologically motivated division between these two genera clearly is not supported by the genetic evidence. An effort is ongoing to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques. The phylogeny of Acipenseridae, as in the cladogram, shows that they evolved from the bony fishes. Approximate dates are from Near et al., 2012. However, multiple recent studies have recovered this arrangement as paraphyletic, instead finding A. oxyrhinchus and A. sturio to form the most basal clade among sturgeons, and all other species being in a separate clade, with the various other species of Acipenser, Scaphirhynchus, Pseudoscaphirhynchus, and Huso to have varying levels of relationship with one another. A potential taxonomy of Acipenseridae is shown here, based on Luo et al. 2019, Nedoluzhko et al. 2020, and Shen et al. 2020. Note the paraphyletic relationships among genera:
The exact placement of Scaphirhynchus varies depending on the study and the methods used, with some placing it within the second most basal clade comprising primarily Pacific species (shown above), whereas others place it in its own clade that is more derived than the secondmost basal clade but less derived than the most derived Atlantic and Central Asian clade. No studies have yet delineated a relationship between it and Pseudoscaphirhynchus. In addition, the exact relationships of the members of the most derived, primarily Atlantic clade vary, although most analyses at least find all the species in it to form a monophyletic clade. The placement of A. sinensis also varies by the study, with some placing it as the only Pacific member of the otherwise Atlantic based most derived clade, whereas others place it with the rest of the Pacific sturgeons as a sister to A. dabryanus. in the rivers that flow into the Black, Azov, and Caspian Seas (Danube, Dnepr, Volga, Ural and Don); the north flowing rivers of Russia that feed the Arctic Ocean (Ob, Yenisei, Lena, Kolyma); in the rivers of Central Asia (Amu Darya and Syr Darya) and Lake Baikal. In the Pacific Ocean, they are found in the Amur River along the Russian Chinese border, on Sakhalin Island, and some rivers in northeast China. Most species are at least partially anadromous, spawning in fresh water and feeding in nutrient rich, brackish waters of estuaries or undergoing significant migrations along coastlines. However, some species have evolved purely freshwater existences, such as the lake sturgeon (Acipenser fulvescens) and the Baikal sturgeon (A. baerii baicalensis), or have been forced into them by human or natural impoundment of their native rivers, as in the case of some subpopulations of white sturgeon (A. transmontanus) in the Columbia River and Siberian sturgeon (A. baerii) in the Ob basin. Physical characteristics
Sturgeons retain several primitive characteristics from the bony fishes. Along with other members of the subclass Chondrostei, they are unique among bony fishes because their skeletons are almost entirely cartilaginous. To maintain structure, sturgeons are one of few organisms to retain a post embryonic notochord that acts like a soft spine running through the body. Notably, however, the cartilagineous skeleton is not a primitive character, but a derived one; sturgeon ancestors had bony skeletons. They also lack vertebral centra, and are partially covered with five lateral rows of scutes rather than scales. They also have four barbels—sensory organs that precede their wide, toothless mouths. They navigate their riverine habitats traveling just off the bottom with their barbels dragging along gravel, or murky substrate. Sturgeon are recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes. The skeletal support for the paired fins of ray finned fish is inside the body wall, although the ray like structures in the webbing of the fins can be seen externally. Sturgeons are among the largest fish: some beluga (Huso huso) in the Caspian Sea reportedly attain over and while for kaluga (H. dauricus) in the Amur River, similar lengths and over weights have been reported. They are also among the longest lived of the fishes, some living well over 100 years and attaining sexual maturity at 20 years or more. The combination of slow growth and reproductive rates and the extremely high value placed on mature, egg bearing females make sturgeon particularly vulnerable to overfishing. Sturgeons are polyploid; some species have four, eight, or 16 sets of chromosomes. Life cycle
Sturgeons are long lived, late maturing fishes. Their average lifespan is 50 to 60 years, and their first spawn does not occur until they are around 15 to 20 years old. Sturgeons are broadcast spawners, and do not spawn every year because they require specific conditions. Those requirements may or may not be met every year due to varying environmental conditions, such as the proper photoperiod in spring, clear water with shallow rock or gravel substrate, where the eggs can adhere, and proper water temperature and flow for oxygenation of the eggs. A single female may release 100,000 to 3 million eggs, but not all will be fertilized. The fertilized eggs become sticky and adhere to the bottom substrate upon contact. Eight to 15 days are needed for the embryos to mature into larval fish. During that time, they are dependent on their yolk sacs for nourishment. River currents carry the larvae downstream into backwater areas, such as oxbows and sloughs, where the free swimming fry spend their first year feeding on insect larvae and crustacea. During their first year of growth, they reach in length and migrate back into the swift flowing currents in the main stem river. Behavior
Sturgeons are primarily benthic feeders, with a diet of shellfish, crustaceans, and small fish. Exceptionally, both Huso'' species, the white sturgeon and the pallid sturgeon feed primarily on other fish as adults. They feed by extending their siphon like mouths to suck food from the benthos. Having no teeth, they are unable to seize prey, though larger individuals and more predatory species can swallow very large prey items, including whole salmon. Sturgeons feed non visually. They are believed to use a combination of sensors, including olfactory, tactile, and chemosensory cues detected by the four barbels, and electroreception using their ampullae of Lorenzini. The electroreceptors are thought to be used in various behaviors such as feeding, mating and migration. Many sturgeons leap completely out of the water, usually making a loud splash which can be heard half a mile away on the surface and probably further under water. Why they do this is not known, but suggested functions include group communication to maintain group cohesion, catching airborne prey, courtship display, or to help shed eggs during spawning. Other plausible explanations include escape from predators, shedding parasites, or to gulp or expel air. Another explanation is that it "simply feels good". in 2015, a 5 year old girl was fatally injured after a sturgeon leapt from the Suwannee River and struck her.
Automatic taxobox
| name = Sturgeon
| image = Acipenser oxyrhynchus (edit). png
| image caption = Atlantic sturgeon(Acipenser oxyrinchus oxyrinchus)
| fossil range =
| taxon = Acipenseridae
| authority = Bonaparte, 1831
| subdivision ranks = Genera
| subdivision =
†Boreiosturion
†Protoscaphirhynchus
†Engdahlichthys
†Anchiacipenser
†Priscosturion
Acipenser (paraphyletic)
Huso
ScaphirhynchusPseudoscaphirhynchus
Sturgeon (from Old English styrġa ultimately from Proto Indo European *str̥(Hx)yón ) is the common name for the 28 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early Jurassic period, some 174 to 201 million years ago. They are one of two living families of the Acipenseriformes alongside paddlefish (Polyodontidae). The family is grouped into four genera: Acipenser (which is paraphyletic, containing many distantly related sturgeon species), Huso, Scaphirhynchus, and Pseudoscaphirhynchus. Two species (A. naccarii and A. dabryanus) may be extinct in the wild, and one (P. fedtschenkoi) may be entirely extinct. Sturgeons are native to subtropical, temperate and sub Arctic rivers, lakes and coastlines of Eurasia and North America. A Maastrichtian age fossil found in Morocco shows that they also once lived in Africa. Sturgeons are long lived, late maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle like body that is smooth skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging in length. The largest sturgeon on record was a beluga female captured in the Volga Delta in 1827, measuring long and weighing Most sturgeons are anadromous bottom feeders, migrating upstream to spawn but spending most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. Several species of sturgeon are harvested for their roe, which is processed into the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction. Evolution
Fossil history
Acipenseriform fishes appeared in the fossil record some 174 to 201 million years ago, during the Early Jurassic, making them some of the earliest extant actinopterygian fishes. True sturgeons appear in the fossil record during the Upper Cretaceous, with amongst the oldest known remains being a partial skull from the Cenomanian (100–94 million years ago) of Alberta, Canada. In that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils. This is explained in part by the long generation interval, tolerance for wide ranges of temperature and salinity, lack of predators due to size and bony plated armor, or scutes, and the abundance of prey items in the benthic environment. They do, however, still share several primitive characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements, and unique jaw suspension. Phylogeny and taxonomy
Despite the existence of a fossil record, full classification and phylogeny of the sturgeon species has been difficult to determine, in part due to the high individual and ontogenic variation, including geographical clines in certain features, such as rostrum shape, number of scutes, and body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. While ray finned fishes (Actinopterygii) have a long evolutionary history culminating in the most familiar fishes, past adaptive evolutionary radiations have left only a few survivors, such as sturgeons and gars. The wide range of the acipenserids and their endangered status have made collection of systematic materials difficult. The factors have led researchers in the past to identify over 40 additional species that were rejected by later scientists. Whether the species in the Acipenser and Huso genera are monophyletic (descended from one ancestor) or paraphyletic (descended from many ancestors) is still unclear, though the morphologically motivated division between these two genera clearly is not supported by the genetic evidence. An effort is ongoing to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques. The phylogeny of Acipenseridae, as in the cladogram, shows that they evolved from the bony fishes. Approximate dates are from Near et al., 2012. However, multiple recent studies have recovered this arrangement as paraphyletic, instead finding A. oxyrhinchus and A. sturio to form the most basal clade among sturgeons, and all other species being in a separate clade, with the various other species of Acipenser, Scaphirhynchus, Pseudoscaphirhynchus, and Huso to have varying levels of relationship with one another. A potential taxonomy of Acipenseridae is shown here, based on Luo et al. 2019, Nedoluzhko et al. 2020, and Shen et al. 2020. Note the paraphyletic relationships among genera:
The exact placement of Scaphirhynchus varies depending on the study and the methods used, with some placing it within the second most basal clade comprising primarily Pacific species (shown above), whereas others place it in its own clade that is more derived than the secondmost basal clade but less derived than the most derived Atlantic and Central Asian clade. No studies have yet delineated a relationship between it and Pseudoscaphirhynchus. In addition, the exact relationships of the members of the most derived, primarily Atlantic clade vary, although most analyses at least find all the species in it to form a monophyletic clade. The placement of A. sinensis also varies by the study, with some placing it as the only Pacific member of the otherwise Atlantic based most derived clade, whereas others place it with the rest of the Pacific sturgeons as a sister to A. dabryanus. in the rivers that flow into the Black, Azov, and Caspian Seas (Danube, Dnepr, Volga, Ural and Don); the north flowing rivers of Russia that feed the Arctic Ocean (Ob, Yenisei, Lena, Kolyma); in the rivers of Central Asia (Amu Darya and Syr Darya) and Lake Baikal. In the Pacific Ocean, they are found in the Amur River along the Russian Chinese border, on Sakhalin Island, and some rivers in northeast China. Most species are at least partially anadromous, spawning in fresh water and feeding in nutrient rich, brackish waters of estuaries or undergoing significant migrations along coastlines. However, some species have evolved purely freshwater existences, such as the lake sturgeon (Acipenser fulvescens) and the Baikal sturgeon (A. baerii baicalensis), or have been forced into them by human or natural impoundment of their native rivers, as in the case of some subpopulations of white sturgeon (A. transmontanus) in the Columbia River and Siberian sturgeon (A. baerii) in the Ob basin. Physical characteristics
Sturgeons retain several primitive characteristics from the bony fishes. Along with other members of the subclass Chondrostei, they are unique among bony fishes because their skeletons are almost entirely cartilaginous. To maintain structure, sturgeons are one of few organisms to retain a post embryonic notochord that acts like a soft spine running through the body. Notably, however, the cartilagineous skeleton is not a primitive character, but a derived one; sturgeon ancestors had bony skeletons. They also lack vertebral centra, and are partially covered with five lateral rows of scutes rather than scales. They also have four barbels—sensory organs that precede their wide, toothless mouths. They navigate their riverine habitats traveling just off the bottom with their barbels dragging along gravel, or murky substrate. Sturgeon are recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes. The skeletal support for the paired fins of ray finned fish is inside the body wall, although the ray like structures in the webbing of the fins can be seen externally. Sturgeons are among the largest fish: some beluga (Huso huso) in the Caspian Sea reportedly attain over and while for kaluga (H. dauricus) in the Amur River, similar lengths and over weights have been reported. They are also among the longest lived of the fishes, some living well over 100 years and attaining sexual maturity at 20 years or more. The combination of slow growth and reproductive rates and the extremely high value placed on mature, egg bearing females make sturgeon particularly vulnerable to overfishing. Sturgeons are polyploid; some species have four, eight, or 16 sets of chromosomes. Life cycle
Sturgeons are long lived, late maturing fishes. Their average lifespan is 50 to 60 years, and their first spawn does not occur until they are around 15 to 20 years old. Sturgeons are broadcast spawners, and do not spawn every year because they require specific conditions. Those requirements may or may not be met every year due to varying environmental conditions, such as the proper photoperiod in spring, clear water with shallow rock or gravel substrate, where the eggs can adhere, and proper water temperature and flow for oxygenation of the eggs. A single female may release 100,000 to 3 million eggs, but not all will be fertilized. The fertilized eggs become sticky and adhere to the bottom substrate upon contact. Eight to 15 days are needed for the embryos to mature into larval fish. During that time, they are dependent on their yolk sacs for nourishment. River currents carry the larvae downstream into backwater areas, such as oxbows and sloughs, where the free swimming fry spend their first year feeding on insect larvae and crustacea. During their first year of growth, they reach in length and migrate back into the swift flowing currents in the main stem river. Behavior
Sturgeons are primarily benthic feeders, with a diet of shellfish, crustaceans, and small fish. Exceptionally, both Huso'' species, the white sturgeon and the pallid sturgeon feed primarily on other fish as adults. They feed by extending their siphon like mouths to suck food from the benthos. Having no teeth, they are unable to seize prey, though larger individuals and more predatory species can swallow very large prey items, including whole salmon. Sturgeons feed non visually. They are believed to use a combination of sensors, including olfactory, tactile, and chemosensory cues detected by the four barbels, and electroreception using their ampullae of Lorenzini. The electroreceptors are thought to be used in various behaviors such as feeding, mating and migration. Many sturgeons leap completely out of the water, usually making a loud splash which can be heard half a mile away on the surface and probably further under water. Why they do this is not known, but suggested functions include group communication to maintain group cohesion, catching airborne prey, courtship display, or to help shed eggs during spawning. Other plausible explanations include escape from predators, shedding parasites, or to gulp or expel air. Another explanation is that it "simply feels good". in 2015, a 5 year old girl was fatally injured after a sturgeon leapt from the Suwannee River and struck her.
Точное положение Scaphirhynchus варьируется в зависимости от исследования и используемых методов, при этом некоторые помещают его в пределах второй наиболее базальной клады, состоящей в основном из тихоокеанских видов (как показано выше), в то время как другие помещают его в собственную кладу, которая более производная, чем вторая наиболее базальная клада, но менее производная, чем наиболее производная атлантическая и центральноазиатская клада. Ни одно исследование пока не определило взаимосвязь между ним и Pseudoscaphirhynchus. Кроме того, точные взаимосвязи членов наиболее производной, в основном атлантической клады, варьируются, хотя большинство анализов, по крайней мере, показывают, что все виды в ней образуют монофилетическую кладу. Положение A. sinensis также варьируется в зависимости от исследования, при этом некоторые помещают его как единственного тихоокеанского члена в противном случае атлантически ориентированной наиболее производной клады, в то время как другие помещают его с остальными тихоокеанскими осетрами как сестринскую группу A. dabryanus. в реках, впадающих в Чёрное, Азовское и Каспийское моря (Дунай, Днепр, Волга, Урал и Дон); в реках, текущих на север России, питающих Северный Ледовитый океан (Обь, Енисей, Лена, Колыма); в реках Центральной Азии (Амударья и Сырдарья) и в озере Байкал. В Тихом океане они встречаются в реке Амур вдоль российско-китайской границы, на острове Сахалин и в некоторых реках северо-восточного Китая. Большинство видов хотя бы частично анадромы, нерестятся в пресной воде и питаются в богатых питательными веществами солоноватых водах эстуариев или совершают значительные миграции вдоль побережья. Однако некоторые виды эволюционировали в чисто пресноводное существование, такие как озёрный осётр (Acipenser fulvescens) и байкальский осётр (A. baerii baicalensis), или были вынуждены к этому в результате строительства человеком или естественного перекрытия их родных рек, как в случае с некоторыми популяциями белого осетра (A. transmontanus) в реке Колумбия и сибирского осетра (A. baerii) в бассейне Оби.
Ray finned fish
Automatic taxobox
| name = Sturgeon
| image = Acipenser oxyrhynchus (edit). png
| image caption = Atlantic sturgeon(Acipenser oxyrinchus oxyrinchus)
| fossil range =
| taxon = Acipenseridae
| authority = Bonaparte, 1831
| subdivision ranks = Genera
| subdivision =
†Boreiosturion
†Protoscaphirhynchus
†Engdahlichthys
†Anchiacipenser
†Priscosturion
Acipenser (paraphyletic)
Huso
ScaphirhynchusPseudoscaphirhynchus
Sturgeon (from Old English styrġa ultimately from Proto Indo European *str̥(Hx)yón ) is the common name for the 28 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early Jurassic period, some 174 to 201 million years ago. They are one of two living families of the Acipenseriformes alongside paddlefish (Polyodontidae). The family is grouped into four genera: Acipenser (which is paraphyletic, containing many distantly related sturgeon species), Huso, Scaphirhynchus, and Pseudoscaphirhynchus. Two species (A. naccarii and A. dabryanus) may be extinct in the wild, and one (P. fedtschenkoi) may be entirely extinct. Sturgeons are native to subtropical, temperate and sub Arctic rivers, lakes and coastlines of Eurasia and North America. A Maastrichtian age fossil found in Morocco shows that they also once lived in Africa. Sturgeons are long lived, late maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle like body that is smooth skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging in length. The largest sturgeon on record was a beluga female captured in the Volga Delta in 1827, measuring long and weighing Most sturgeons are anadromous bottom feeders, migrating upstream to spawn but spending most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. Several species of sturgeon are harvested for their roe, which is processed into the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction. Evolution
Fossil history
Acipenseriform fishes appeared in the fossil record some 174 to 201 million years ago, during the Early Jurassic, making them some of the earliest extant actinopterygian fishes. True sturgeons appear in the fossil record during the Upper Cretaceous, with amongst the oldest known remains being a partial skull from the Cenomanian (100–94 million years ago) of Alberta, Canada. In that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils. This is explained in part by the long generation interval, tolerance for wide ranges of temperature and salinity, lack of predators due to size and bony plated armor, or scutes, and the abundance of prey items in the benthic environment. They do, however, still share several primitive characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements, and unique jaw suspension. Phylogeny and taxonomy
Despite the existence of a fossil record, full classification and phylogeny of the sturgeon species has been difficult to determine, in part due to the high individual and ontogenic variation, including geographical clines in certain features, such as rostrum shape, number of scutes, and body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. While ray finned fishes (Actinopterygii) have a long evolutionary history culminating in the most familiar fishes, past adaptive evolutionary radiations have left only a few survivors, such as sturgeons and gars. The wide range of the acipenserids and their endangered status have made collection of systematic materials difficult. The factors have led researchers in the past to identify over 40 additional species that were rejected by later scientists. Whether the species in the Acipenser and Huso genera are monophyletic (descended from one ancestor) or paraphyletic (descended from many ancestors) is still unclear, though the morphologically motivated division between these two genera clearly is not supported by the genetic evidence. An effort is ongoing to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques. The phylogeny of Acipenseridae, as in the cladogram, shows that they evolved from the bony fishes. Approximate dates are from Near et al., 2012. However, multiple recent studies have recovered this arrangement as paraphyletic, instead finding A. oxyrhinchus and A. sturio to form the most basal clade among sturgeons, and all other species being in a separate clade, with the various other species of Acipenser, Scaphirhynchus, Pseudoscaphirhynchus, and Huso to have varying levels of relationship with one another. A potential taxonomy of Acipenseridae is shown here, based on Luo et al. 2019, Nedoluzhko et al. 2020, and Shen et al. 2020. Note the paraphyletic relationships among genera:
The exact placement of Scaphirhynchus varies depending on the study and the methods used, with some placing it within the second most basal clade comprising primarily Pacific species (shown above), whereas others place it in its own clade that is more derived than the secondmost basal clade but less derived than the most derived Atlantic and Central Asian clade. No studies have yet delineated a relationship between it and Pseudoscaphirhynchus. In addition, the exact relationships of the members of the most derived, primarily Atlantic clade vary, although most analyses at least find all the species in it to form a monophyletic clade. The placement of A. sinensis also varies by the study, with some placing it as the only Pacific member of the otherwise Atlantic based most derived clade, whereas others place it with the rest of the Pacific sturgeons as a sister to A. dabryanus. in the rivers that flow into the Black, Azov, and Caspian Seas (Danube, Dnepr, Volga, Ural and Don); the north flowing rivers of Russia that feed the Arctic Ocean (Ob, Yenisei, Lena, Kolyma); in the rivers of Central Asia (Amu Darya and Syr Darya) and Lake Baikal. In the Pacific Ocean, they are found in the Amur River along the Russian Chinese border, on Sakhalin Island, and some rivers in northeast China. Most species are at least partially anadromous, spawning in fresh water and feeding in nutrient rich, brackish waters of estuaries or undergoing significant migrations along coastlines. However, some species have evolved purely freshwater existences, such as the lake sturgeon (Acipenser fulvescens) and the Baikal sturgeon (A. baerii baicalensis), or have been forced into them by human or natural impoundment of their native rivers, as in the case of some subpopulations of white sturgeon (A. transmontanus) in the Columbia River and Siberian sturgeon (A. baerii) in the Ob basin. Physical characteristics
Sturgeons retain several primitive characteristics from the bony fishes. Along with other members of the subclass Chondrostei, they are unique among bony fishes because their skeletons are almost entirely cartilaginous. To maintain structure, sturgeons are one of few organisms to retain a post embryonic notochord that acts like a soft spine running through the body. Notably, however, the cartilagineous skeleton is not a primitive character, but a derived one; sturgeon ancestors had bony skeletons. They also lack vertebral centra, and are partially covered with five lateral rows of scutes rather than scales. They also have four barbels—sensory organs that precede their wide, toothless mouths. They navigate their riverine habitats traveling just off the bottom with their barbels dragging along gravel, or murky substrate. Sturgeon are recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes. The skeletal support for the paired fins of ray finned fish is inside the body wall, although the ray like structures in the webbing of the fins can be seen externally. Sturgeons are among the largest fish: some beluga (Huso huso) in the Caspian Sea reportedly attain over and while for kaluga (H. dauricus) in the Amur River, similar lengths and over weights have been reported. They are also among the longest lived of the fishes, some living well over 100 years and attaining sexual maturity at 20 years or more. The combination of slow growth and reproductive rates and the extremely high value placed on mature, egg bearing females make sturgeon particularly vulnerable to overfishing. Sturgeons are polyploid; some species have four, eight, or 16 sets of chromosomes. Life cycle
Sturgeons are long lived, late maturing fishes. Their average lifespan is 50 to 60 years, and their first spawn does not occur until they are around 15 to 20 years old. Sturgeons are broadcast spawners, and do not spawn every year because they require specific conditions. Those requirements may or may not be met every year due to varying environmental conditions, such as the proper photoperiod in spring, clear water with shallow rock or gravel substrate, where the eggs can adhere, and proper water temperature and flow for oxygenation of the eggs. A single female may release 100,000 to 3 million eggs, but not all will be fertilized. The fertilized eggs become sticky and adhere to the bottom substrate upon contact. Eight to 15 days are needed for the embryos to mature into larval fish. During that time, they are dependent on their yolk sacs for nourishment. River currents carry the larvae downstream into backwater areas, such as oxbows and sloughs, where the free swimming fry spend their first year feeding on insect larvae and crustacea. During their first year of growth, they reach in length and migrate back into the swift flowing currents in the main stem river. Behavior
Sturgeons are primarily benthic feeders, with a diet of shellfish, crustaceans, and small fish. Exceptionally, both Huso'' species, the white sturgeon and the pallid sturgeon feed primarily on other fish as adults. They feed by extending their siphon like mouths to suck food from the benthos. Having no teeth, they are unable to seize prey, though larger individuals and more predatory species can swallow very large prey items, including whole salmon. Sturgeons feed non visually. They are believed to use a combination of sensors, including olfactory, tactile, and chemosensory cues detected by the four barbels, and electroreception using their ampullae of Lorenzini. The electroreceptors are thought to be used in various behaviors such as feeding, mating and migration. Many sturgeons leap completely out of the water, usually making a loud splash which can be heard half a mile away on the surface and probably further under water. Why they do this is not known, but suggested functions include group communication to maintain group cohesion, catching airborne prey, courtship display, or to help shed eggs during spawning. Other plausible explanations include escape from predators, shedding parasites, or to gulp or expel air. Another explanation is that it "simply feels good". in 2015, a 5 year old girl was fatally injured after a sturgeon leapt from the Suwannee River and struck her.
Automatic taxobox
| name = Sturgeon
| image = Acipenser oxyrhynchus (edit). png
| image caption = Atlantic sturgeon(Acipenser oxyrinchus oxyrinchus)
| fossil range =
| taxon = Acipenseridae
| authority = Bonaparte, 1831
| subdivision ranks = Genera
| subdivision =
†Boreiosturion
†Protoscaphirhynchus
†Engdahlichthys
†Anchiacipenser
†Priscosturion
Acipenser (paraphyletic)
Huso
ScaphirhynchusPseudoscaphirhynchus
Sturgeon (from Old English styrġa ultimately from Proto Indo European *str̥(Hx)yón ) is the common name for the 28 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early Jurassic period, some 174 to 201 million years ago. They are one of two living families of the Acipenseriformes alongside paddlefish (Polyodontidae). The family is grouped into four genera: Acipenser (which is paraphyletic, containing many distantly related sturgeon species), Huso, Scaphirhynchus, and Pseudoscaphirhynchus. Two species (A. naccarii and A. dabryanus) may be extinct in the wild, and one (P. fedtschenkoi) may be entirely extinct. Sturgeons are native to subtropical, temperate and sub Arctic rivers, lakes and coastlines of Eurasia and North America. A Maastrichtian age fossil found in Morocco shows that they also once lived in Africa. Sturgeons are long lived, late maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle like body that is smooth skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging in length. The largest sturgeon on record was a beluga female captured in the Volga Delta in 1827, measuring long and weighing Most sturgeons are anadromous bottom feeders, migrating upstream to spawn but spending most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. Several species of sturgeon are harvested for their roe, which is processed into the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction. Evolution
Fossil history
Acipenseriform fishes appeared in the fossil record some 174 to 201 million years ago, during the Early Jurassic, making them some of the earliest extant actinopterygian fishes. True sturgeons appear in the fossil record during the Upper Cretaceous, with amongst the oldest known remains being a partial skull from the Cenomanian (100–94 million years ago) of Alberta, Canada. In that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils. This is explained in part by the long generation interval, tolerance for wide ranges of temperature and salinity, lack of predators due to size and bony plated armor, or scutes, and the abundance of prey items in the benthic environment. They do, however, still share several primitive characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements, and unique jaw suspension. Phylogeny and taxonomy
Despite the existence of a fossil record, full classification and phylogeny of the sturgeon species has been difficult to determine, in part due to the high individual and ontogenic variation, including geographical clines in certain features, such as rostrum shape, number of scutes, and body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. While ray finned fishes (Actinopterygii) have a long evolutionary history culminating in the most familiar fishes, past adaptive evolutionary radiations have left only a few survivors, such as sturgeons and gars. The wide range of the acipenserids and their endangered status have made collection of systematic materials difficult. The factors have led researchers in the past to identify over 40 additional species that were rejected by later scientists. Whether the species in the Acipenser and Huso genera are monophyletic (descended from one ancestor) or paraphyletic (descended from many ancestors) is still unclear, though the morphologically motivated division between these two genera clearly is not supported by the genetic evidence. An effort is ongoing to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques. The phylogeny of Acipenseridae, as in the cladogram, shows that they evolved from the bony fishes. Approximate dates are from Near et al., 2012. However, multiple recent studies have recovered this arrangement as paraphyletic, instead finding A. oxyrhinchus and A. sturio to form the most basal clade among sturgeons, and all other species being in a separate clade, with the various other species of Acipenser, Scaphirhynchus, Pseudoscaphirhynchus, and Huso to have varying levels of relationship with one another. A potential taxonomy of Acipenseridae is shown here, based on Luo et al. 2019, Nedoluzhko et al. 2020, and Shen et al. 2020. Note the paraphyletic relationships among genera:
The exact placement of Scaphirhynchus varies depending on the study and the methods used, with some placing it within the second most basal clade comprising primarily Pacific species (shown above), whereas others place it in its own clade that is more derived than the secondmost basal clade but less derived than the most derived Atlantic and Central Asian clade. No studies have yet delineated a relationship between it and Pseudoscaphirhynchus. In addition, the exact relationships of the members of the most derived, primarily Atlantic clade vary, although most analyses at least find all the species in it to form a monophyletic clade. The placement of A. sinensis also varies by the study, with some placing it as the only Pacific member of the otherwise Atlantic based most derived clade, whereas others place it with the rest of the Pacific sturgeons as a sister to A. dabryanus. in the rivers that flow into the Black, Azov, and Caspian Seas (Danube, Dnepr, Volga, Ural and Don); the north flowing rivers of Russia that feed the Arctic Ocean (Ob, Yenisei, Lena, Kolyma); in the rivers of Central Asia (Amu Darya and Syr Darya) and Lake Baikal. In the Pacific Ocean, they are found in the Amur River along the Russian Chinese border, on Sakhalin Island, and some rivers in northeast China. Most species are at least partially anadromous, spawning in fresh water and feeding in nutrient rich, brackish waters of estuaries or undergoing significant migrations along coastlines. However, some species have evolved purely freshwater existences, such as the lake sturgeon (Acipenser fulvescens) and the Baikal sturgeon (A. baerii baicalensis), or have been forced into them by human or natural impoundment of their native rivers, as in the case of some subpopulations of white sturgeon (A. transmontanus) in the Columbia River and Siberian sturgeon (A. baerii) in the Ob basin. Physical characteristics
Sturgeons retain several primitive characteristics from the bony fishes. Along with other members of the subclass Chondrostei, they are unique among bony fishes because their skeletons are almost entirely cartilaginous. To maintain structure, sturgeons are one of few organisms to retain a post embryonic notochord that acts like a soft spine running through the body. Notably, however, the cartilagineous skeleton is not a primitive character, but a derived one; sturgeon ancestors had bony skeletons. They also lack vertebral centra, and are partially covered with five lateral rows of scutes rather than scales. They also have four barbels—sensory organs that precede their wide, toothless mouths. They navigate their riverine habitats traveling just off the bottom with their barbels dragging along gravel, or murky substrate. Sturgeon are recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes. The skeletal support for the paired fins of ray finned fish is inside the body wall, although the ray like structures in the webbing of the fins can be seen externally. Sturgeons are among the largest fish: some beluga (Huso huso) in the Caspian Sea reportedly attain over and while for kaluga (H. dauricus) in the Amur River, similar lengths and over weights have been reported. They are also among the longest lived of the fishes, some living well over 100 years and attaining sexual maturity at 20 years or more. The combination of slow growth and reproductive rates and the extremely high value placed on mature, egg bearing females make sturgeon particularly vulnerable to overfishing. Sturgeons are polyploid; some species have four, eight, or 16 sets of chromosomes. Life cycle
Sturgeons are long lived, late maturing fishes. Their average lifespan is 50 to 60 years, and their first spawn does not occur until they are around 15 to 20 years old. Sturgeons are broadcast spawners, and do not spawn every year because they require specific conditions. Those requirements may or may not be met every year due to varying environmental conditions, such as the proper photoperiod in spring, clear water with shallow rock or gravel substrate, where the eggs can adhere, and proper water temperature and flow for oxygenation of the eggs. A single female may release 100,000 to 3 million eggs, but not all will be fertilized. The fertilized eggs become sticky and adhere to the bottom substrate upon contact. Eight to 15 days are needed for the embryos to mature into larval fish. During that time, they are dependent on their yolk sacs for nourishment. River currents carry the larvae downstream into backwater areas, such as oxbows and sloughs, where the free swimming fry spend their first year feeding on insect larvae and crustacea. During their first year of growth, they reach in length and migrate back into the swift flowing currents in the main stem river. Behavior
Sturgeons are primarily benthic feeders, with a diet of shellfish, crustaceans, and small fish. Exceptionally, both Huso'' species, the white sturgeon and the pallid sturgeon feed primarily on other fish as adults. They feed by extending their siphon like mouths to suck food from the benthos. Having no teeth, they are unable to seize prey, though larger individuals and more predatory species can swallow very large prey items, including whole salmon. Sturgeons feed non visually. They are believed to use a combination of sensors, including olfactory, tactile, and chemosensory cues detected by the four barbels, and electroreception using their ampullae of Lorenzini. The electroreceptors are thought to be used in various behaviors such as feeding, mating and migration. Many sturgeons leap completely out of the water, usually making a loud splash which can be heard half a mile away on the surface and probably further under water. Why they do this is not known, but suggested functions include group communication to maintain group cohesion, catching airborne prey, courtship display, or to help shed eggs during spawning. Other plausible explanations include escape from predators, shedding parasites, or to gulp or expel air. Another explanation is that it "simply feels good". in 2015, a 5 year old girl was fatally injured after a sturgeon leapt from the Suwannee River and struck her.
Физические характеристики
Ray finned fish
Automatic taxobox
| name = Sturgeon
| image = Acipenser oxyrhynchus (edit). png
| image caption = Atlantic sturgeon(Acipenser oxyrinchus oxyrinchus)
| fossil range =
| taxon = Acipenseridae
| authority = Bonaparte, 1831
| subdivision ranks = Genera
| subdivision =
†Boreiosturion
†Protoscaphirhynchus
†Engdahlichthys
†Anchiacipenser
†Priscosturion
Acipenser (paraphyletic)
Huso
ScaphirhynchusPseudoscaphirhynchus
Sturgeon (from Old English styrġa ultimately from Proto Indo European *str̥(Hx)yón ) is the common name for the 28 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early Jurassic period, some 174 to 201 million years ago. They are one of two living families of the Acipenseriformes alongside paddlefish (Polyodontidae). The family is grouped into four genera: Acipenser (which is paraphyletic, containing many distantly related sturgeon species), Huso, Scaphirhynchus, and Pseudoscaphirhynchus. Two species (A. naccarii and A. dabryanus) may be extinct in the wild, and one (P. fedtschenkoi) may be entirely extinct. Sturgeons are native to subtropical, temperate and sub Arctic rivers, lakes and coastlines of Eurasia and North America. A Maastrichtian age fossil found in Morocco shows that they also once lived in Africa. Sturgeons are long lived, late maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle like body that is smooth skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging in length. The largest sturgeon on record was a beluga female captured in the Volga Delta in 1827, measuring long and weighing Most sturgeons are anadromous bottom feeders, migrating upstream to spawn but spending most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. Several species of sturgeon are harvested for their roe, which is processed into the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction. Evolution
Fossil history
Acipenseriform fishes appeared in the fossil record some 174 to 201 million years ago, during the Early Jurassic, making them some of the earliest extant actinopterygian fishes. True sturgeons appear in the fossil record during the Upper Cretaceous, with amongst the oldest known remains being a partial skull from the Cenomanian (100–94 million years ago) of Alberta, Canada. In that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils. This is explained in part by the long generation interval, tolerance for wide ranges of temperature and salinity, lack of predators due to size and bony plated armor, or scutes, and the abundance of prey items in the benthic environment. They do, however, still share several primitive characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements, and unique jaw suspension. Phylogeny and taxonomy
Despite the existence of a fossil record, full classification and phylogeny of the sturgeon species has been difficult to determine, in part due to the high individual and ontogenic variation, including geographical clines in certain features, such as rostrum shape, number of scutes, and body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. While ray finned fishes (Actinopterygii) have a long evolutionary history culminating in the most familiar fishes, past adaptive evolutionary radiations have left only a few survivors, such as sturgeons and gars. The wide range of the acipenserids and their endangered status have made collection of systematic materials difficult. The factors have led researchers in the past to identify over 40 additional species that were rejected by later scientists. Whether the species in the Acipenser and Huso genera are monophyletic (descended from one ancestor) or paraphyletic (descended from many ancestors) is still unclear, though the morphologically motivated division between these two genera clearly is not supported by the genetic evidence. An effort is ongoing to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques. The phylogeny of Acipenseridae, as in the cladogram, shows that they evolved from the bony fishes. Approximate dates are from Near et al., 2012. However, multiple recent studies have recovered this arrangement as paraphyletic, instead finding A. oxyrhinchus and A. sturio to form the most basal clade among sturgeons, and all other species being in a separate clade, with the various other species of Acipenser, Scaphirhynchus, Pseudoscaphirhynchus, and Huso to have varying levels of relationship with one another. A potential taxonomy of Acipenseridae is shown here, based on Luo et al. 2019, Nedoluzhko et al. 2020, and Shen et al. 2020. Note the paraphyletic relationships among genera:
The exact placement of Scaphirhynchus varies depending on the study and the methods used, with some placing it within the second most basal clade comprising primarily Pacific species (shown above), whereas others place it in its own clade that is more derived than the secondmost basal clade but less derived than the most derived Atlantic and Central Asian clade. No studies have yet delineated a relationship between it and Pseudoscaphirhynchus. In addition, the exact relationships of the members of the most derived, primarily Atlantic clade vary, although most analyses at least find all the species in it to form a monophyletic clade. The placement of A. sinensis also varies by the study, with some placing it as the only Pacific member of the otherwise Atlantic based most derived clade, whereas others place it with the rest of the Pacific sturgeons as a sister to A. dabryanus. in the rivers that flow into the Black, Azov, and Caspian Seas (Danube, Dnepr, Volga, Ural and Don); the north flowing rivers of Russia that feed the Arctic Ocean (Ob, Yenisei, Lena, Kolyma); in the rivers of Central Asia (Amu Darya and Syr Darya) and Lake Baikal. In the Pacific Ocean, they are found in the Amur River along the Russian Chinese border, on Sakhalin Island, and some rivers in northeast China. Most species are at least partially anadromous, spawning in fresh water and feeding in nutrient rich, brackish waters of estuaries or undergoing significant migrations along coastlines. However, some species have evolved purely freshwater existences, such as the lake sturgeon (Acipenser fulvescens) and the Baikal sturgeon (A. baerii baicalensis), or have been forced into them by human or natural impoundment of their native rivers, as in the case of some subpopulations of white sturgeon (A. transmontanus) in the Columbia River and Siberian sturgeon (A. baerii) in the Ob basin. Physical characteristics
Sturgeons retain several primitive characteristics from the bony fishes. Along with other members of the subclass Chondrostei, they are unique among bony fishes because their skeletons are almost entirely cartilaginous. To maintain structure, sturgeons are one of few organisms to retain a post embryonic notochord that acts like a soft spine running through the body. Notably, however, the cartilagineous skeleton is not a primitive character, but a derived one; sturgeon ancestors had bony skeletons. They also lack vertebral centra, and are partially covered with five lateral rows of scutes rather than scales. They also have four barbels—sensory organs that precede their wide, toothless mouths. They navigate their riverine habitats traveling just off the bottom with their barbels dragging along gravel, or murky substrate. Sturgeon are recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes. The skeletal support for the paired fins of ray finned fish is inside the body wall, although the ray like structures in the webbing of the fins can be seen externally. Sturgeons are among the largest fish: some beluga (Huso huso) in the Caspian Sea reportedly attain over and while for kaluga (H. dauricus) in the Amur River, similar lengths and over weights have been reported. They are also among the longest lived of the fishes, some living well over 100 years and attaining sexual maturity at 20 years or more. The combination of slow growth and reproductive rates and the extremely high value placed on mature, egg bearing females make sturgeon particularly vulnerable to overfishing. Sturgeons are polyploid; some species have four, eight, or 16 sets of chromosomes. Life cycle
Sturgeons are long lived, late maturing fishes. Their average lifespan is 50 to 60 years, and their first spawn does not occur until they are around 15 to 20 years old. Sturgeons are broadcast spawners, and do not spawn every year because they require specific conditions. Those requirements may or may not be met every year due to varying environmental conditions, such as the proper photoperiod in spring, clear water with shallow rock or gravel substrate, where the eggs can adhere, and proper water temperature and flow for oxygenation of the eggs. A single female may release 100,000 to 3 million eggs, but not all will be fertilized. The fertilized eggs become sticky and adhere to the bottom substrate upon contact. Eight to 15 days are needed for the embryos to mature into larval fish. During that time, they are dependent on their yolk sacs for nourishment. River currents carry the larvae downstream into backwater areas, such as oxbows and sloughs, where the free swimming fry spend their first year feeding on insect larvae and crustacea. During their first year of growth, they reach in length and migrate back into the swift flowing currents in the main stem river. Behavior
Sturgeons are primarily benthic feeders, with a diet of shellfish, crustaceans, and small fish. Exceptionally, both Huso'' species, the white sturgeon and the pallid sturgeon feed primarily on other fish as adults. They feed by extending their siphon like mouths to suck food from the benthos. Having no teeth, they are unable to seize prey, though larger individuals and more predatory species can swallow very large prey items, including whole salmon. Sturgeons feed non visually. They are believed to use a combination of sensors, including olfactory, tactile, and chemosensory cues detected by the four barbels, and electroreception using their ampullae of Lorenzini. The electroreceptors are thought to be used in various behaviors such as feeding, mating and migration. Many sturgeons leap completely out of the water, usually making a loud splash which can be heard half a mile away on the surface and probably further under water. Why they do this is not known, but suggested functions include group communication to maintain group cohesion, catching airborne prey, courtship display, or to help shed eggs during spawning. Other plausible explanations include escape from predators, shedding parasites, or to gulp or expel air. Another explanation is that it "simply feels good". in 2015, a 5 year old girl was fatally injured after a sturgeon leapt from the Suwannee River and struck her.
Automatic taxobox
| name = Sturgeon
| image = Acipenser oxyrhynchus (edit). png
| image caption = Atlantic sturgeon(Acipenser oxyrinchus oxyrinchus)
| fossil range =
| taxon = Acipenseridae
| authority = Bonaparte, 1831
| subdivision ranks = Genera
| subdivision =
†Boreiosturion
†Protoscaphirhynchus
†Engdahlichthys
†Anchiacipenser
†Priscosturion
Acipenser (paraphyletic)
Huso
ScaphirhynchusPseudoscaphirhynchus
Sturgeon (from Old English styrġa ultimately from Proto Indo European *str̥(Hx)yón ) is the common name for the 28 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early Jurassic period, some 174 to 201 million years ago. They are one of two living families of the Acipenseriformes alongside paddlefish (Polyodontidae). The family is grouped into four genera: Acipenser (which is paraphyletic, containing many distantly related sturgeon species), Huso, Scaphirhynchus, and Pseudoscaphirhynchus. Two species (A. naccarii and A. dabryanus) may be extinct in the wild, and one (P. fedtschenkoi) may be entirely extinct. Sturgeons are native to subtropical, temperate and sub Arctic rivers, lakes and coastlines of Eurasia and North America. A Maastrichtian age fossil found in Morocco shows that they also once lived in Africa. Sturgeons are long lived, late maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle like body that is smooth skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging in length. The largest sturgeon on record was a beluga female captured in the Volga Delta in 1827, measuring long and weighing Most sturgeons are anadromous bottom feeders, migrating upstream to spawn but spending most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. Several species of sturgeon are harvested for their roe, which is processed into the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction. Evolution
Fossil history
Acipenseriform fishes appeared in the fossil record some 174 to 201 million years ago, during the Early Jurassic, making them some of the earliest extant actinopterygian fishes. True sturgeons appear in the fossil record during the Upper Cretaceous, with amongst the oldest known remains being a partial skull from the Cenomanian (100–94 million years ago) of Alberta, Canada. In that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils. This is explained in part by the long generation interval, tolerance for wide ranges of temperature and salinity, lack of predators due to size and bony plated armor, or scutes, and the abundance of prey items in the benthic environment. They do, however, still share several primitive characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements, and unique jaw suspension. Phylogeny and taxonomy
Despite the existence of a fossil record, full classification and phylogeny of the sturgeon species has been difficult to determine, in part due to the high individual and ontogenic variation, including geographical clines in certain features, such as rostrum shape, number of scutes, and body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. While ray finned fishes (Actinopterygii) have a long evolutionary history culminating in the most familiar fishes, past adaptive evolutionary radiations have left only a few survivors, such as sturgeons and gars. The wide range of the acipenserids and their endangered status have made collection of systematic materials difficult. The factors have led researchers in the past to identify over 40 additional species that were rejected by later scientists. Whether the species in the Acipenser and Huso genera are monophyletic (descended from one ancestor) or paraphyletic (descended from many ancestors) is still unclear, though the morphologically motivated division between these two genera clearly is not supported by the genetic evidence. An effort is ongoing to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques. The phylogeny of Acipenseridae, as in the cladogram, shows that they evolved from the bony fishes. Approximate dates are from Near et al., 2012. However, multiple recent studies have recovered this arrangement as paraphyletic, instead finding A. oxyrhinchus and A. sturio to form the most basal clade among sturgeons, and all other species being in a separate clade, with the various other species of Acipenser, Scaphirhynchus, Pseudoscaphirhynchus, and Huso to have varying levels of relationship with one another. A potential taxonomy of Acipenseridae is shown here, based on Luo et al. 2019, Nedoluzhko et al. 2020, and Shen et al. 2020. Note the paraphyletic relationships among genera:
The exact placement of Scaphirhynchus varies depending on the study and the methods used, with some placing it within the second most basal clade comprising primarily Pacific species (shown above), whereas others place it in its own clade that is more derived than the secondmost basal clade but less derived than the most derived Atlantic and Central Asian clade. No studies have yet delineated a relationship between it and Pseudoscaphirhynchus. In addition, the exact relationships of the members of the most derived, primarily Atlantic clade vary, although most analyses at least find all the species in it to form a monophyletic clade. The placement of A. sinensis also varies by the study, with some placing it as the only Pacific member of the otherwise Atlantic based most derived clade, whereas others place it with the rest of the Pacific sturgeons as a sister to A. dabryanus. in the rivers that flow into the Black, Azov, and Caspian Seas (Danube, Dnepr, Volga, Ural and Don); the north flowing rivers of Russia that feed the Arctic Ocean (Ob, Yenisei, Lena, Kolyma); in the rivers of Central Asia (Amu Darya and Syr Darya) and Lake Baikal. In the Pacific Ocean, they are found in the Amur River along the Russian Chinese border, on Sakhalin Island, and some rivers in northeast China. Most species are at least partially anadromous, spawning in fresh water and feeding in nutrient rich, brackish waters of estuaries or undergoing significant migrations along coastlines. However, some species have evolved purely freshwater existences, such as the lake sturgeon (Acipenser fulvescens) and the Baikal sturgeon (A. baerii baicalensis), or have been forced into them by human or natural impoundment of their native rivers, as in the case of some subpopulations of white sturgeon (A. transmontanus) in the Columbia River and Siberian sturgeon (A. baerii) in the Ob basin. Physical characteristics
Sturgeons retain several primitive characteristics from the bony fishes. Along with other members of the subclass Chondrostei, they are unique among bony fishes because their skeletons are almost entirely cartilaginous. To maintain structure, sturgeons are one of few organisms to retain a post embryonic notochord that acts like a soft spine running through the body. Notably, however, the cartilagineous skeleton is not a primitive character, but a derived one; sturgeon ancestors had bony skeletons. They also lack vertebral centra, and are partially covered with five lateral rows of scutes rather than scales. They also have four barbels—sensory organs that precede their wide, toothless mouths. They navigate their riverine habitats traveling just off the bottom with their barbels dragging along gravel, or murky substrate. Sturgeon are recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes. The skeletal support for the paired fins of ray finned fish is inside the body wall, although the ray like structures in the webbing of the fins can be seen externally. Sturgeons are among the largest fish: some beluga (Huso huso) in the Caspian Sea reportedly attain over and while for kaluga (H. dauricus) in the Amur River, similar lengths and over weights have been reported. They are also among the longest lived of the fishes, some living well over 100 years and attaining sexual maturity at 20 years or more. The combination of slow growth and reproductive rates and the extremely high value placed on mature, egg bearing females make sturgeon particularly vulnerable to overfishing. Sturgeons are polyploid; some species have four, eight, or 16 sets of chromosomes. Life cycle
Sturgeons are long lived, late maturing fishes. Their average lifespan is 50 to 60 years, and their first spawn does not occur until they are around 15 to 20 years old. Sturgeons are broadcast spawners, and do not spawn every year because they require specific conditions. Those requirements may or may not be met every year due to varying environmental conditions, such as the proper photoperiod in spring, clear water with shallow rock or gravel substrate, where the eggs can adhere, and proper water temperature and flow for oxygenation of the eggs. A single female may release 100,000 to 3 million eggs, but not all will be fertilized. The fertilized eggs become sticky and adhere to the bottom substrate upon contact. Eight to 15 days are needed for the embryos to mature into larval fish. During that time, they are dependent on their yolk sacs for nourishment. River currents carry the larvae downstream into backwater areas, such as oxbows and sloughs, where the free swimming fry spend their first year feeding on insect larvae and crustacea. During their first year of growth, they reach in length and migrate back into the swift flowing currents in the main stem river. Behavior
Sturgeons are primarily benthic feeders, with a diet of shellfish, crustaceans, and small fish. Exceptionally, both Huso'' species, the white sturgeon and the pallid sturgeon feed primarily on other fish as adults. They feed by extending their siphon like mouths to suck food from the benthos. Having no teeth, they are unable to seize prey, though larger individuals and more predatory species can swallow very large prey items, including whole salmon. Sturgeons feed non visually. They are believed to use a combination of sensors, including olfactory, tactile, and chemosensory cues detected by the four barbels, and electroreception using their ampullae of Lorenzini. The electroreceptors are thought to be used in various behaviors such as feeding, mating and migration. Many sturgeons leap completely out of the water, usually making a loud splash which can be heard half a mile away on the surface and probably further under water. Why they do this is not known, but suggested functions include group communication to maintain group cohesion, catching airborne prey, courtship display, or to help shed eggs during spawning. Other plausible explanations include escape from predators, shedding parasites, or to gulp or expel air. Another explanation is that it "simply feels good". in 2015, a 5 year old girl was fatally injured after a sturgeon leapt from the Suwannee River and struck her.
Стержни сохраняют несколько примитивных характеристик от костных рыб. Наряду с другими членами подкласса Chondrostei, они уникальны среди костных рыб тем, что их скелеты почти полностью хрящевые. Для поддержания структуры осетры — одни из немногих организмов, сохраняющих постэмбриональную хорду, которая действует как мягкий позвоночник, проходящий через тело. Однако следует отметить, что хрящевой скелет не является примитивным признаком, а производным; предки осетров имели костные скелеты. У них также отсутствуют позвоночные центры, и они…
Ray finned fish
Automatic taxobox
| name = Sturgeon
| image = Acipenser oxyrhynchus (edit). png
| image caption = Atlantic sturgeon(Acipenser oxyrinchus oxyrinchus)
| fossil range =
| taxon = Acipenseridae
| authority = Bonaparte, 1831
| subdivision ranks = Genera
| subdivision =
†Boreiosturion
†Protoscaphirhynchus
†Engdahlichthys
†Anchiacipenser
†Priscosturion
Acipenser (paraphyletic)
Huso
ScaphirhynchusPseudoscaphirhynchus
Sturgeon (from Old English styrġa ultimately from Proto Indo European *str̥(Hx)yón ) is the common name for the 28 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early Jurassic period, some 174 to 201 million years ago. They are one of two living families of the Acipenseriformes alongside paddlefish (Polyodontidae). The family is grouped into four genera: Acipenser (which is paraphyletic, containing many distantly related sturgeon species), Huso, Scaphirhynchus, and Pseudoscaphirhynchus. Two species (A. naccarii and A. dabryanus) may be extinct in the wild, and one (P. fedtschenkoi) may be entirely extinct. Sturgeons are native to subtropical, temperate and sub Arctic rivers, lakes and coastlines of Eurasia and North America. A Maastrichtian age fossil found in Morocco shows that they also once lived in Africa. Sturgeons are long lived, late maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle like body that is smooth skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging in length. The largest sturgeon on record was a beluga female captured in the Volga Delta in 1827, measuring long and weighing Most sturgeons are anadromous bottom feeders, migrating upstream to spawn but spending most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. Several species of sturgeon are harvested for their roe, which is processed into the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction. Evolution
Fossil history
Acipenseriform fishes appeared in the fossil record some 174 to 201 million years ago, during the Early Jurassic, making them some of the earliest extant actinopterygian fishes. True sturgeons appear in the fossil record during the Upper Cretaceous, with amongst the oldest known remains being a partial skull from the Cenomanian (100–94 million years ago) of Alberta, Canada. In that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils. This is explained in part by the long generation interval, tolerance for wide ranges of temperature and salinity, lack of predators due to size and bony plated armor, or scutes, and the abundance of prey items in the benthic environment. They do, however, still share several primitive characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements, and unique jaw suspension. Phylogeny and taxonomy
Despite the existence of a fossil record, full classification and phylogeny of the sturgeon species has been difficult to determine, in part due to the high individual and ontogenic variation, including geographical clines in certain features, such as rostrum shape, number of scutes, and body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. While ray finned fishes (Actinopterygii) have a long evolutionary history culminating in the most familiar fishes, past adaptive evolutionary radiations have left only a few survivors, such as sturgeons and gars. The wide range of the acipenserids and their endangered status have made collection of systematic materials difficult. The factors have led researchers in the past to identify over 40 additional species that were rejected by later scientists. Whether the species in the Acipenser and Huso genera are monophyletic (descended from one ancestor) or paraphyletic (descended from many ancestors) is still unclear, though the morphologically motivated division between these two genera clearly is not supported by the genetic evidence. An effort is ongoing to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques. The phylogeny of Acipenseridae, as in the cladogram, shows that they evolved from the bony fishes. Approximate dates are from Near et al., 2012. However, multiple recent studies have recovered this arrangement as paraphyletic, instead finding A. oxyrhinchus and A. sturio to form the most basal clade among sturgeons, and all other species being in a separate clade, with the various other species of Acipenser, Scaphirhynchus, Pseudoscaphirhynchus, and Huso to have varying levels of relationship with one another. A potential taxonomy of Acipenseridae is shown here, based on Luo et al. 2019, Nedoluzhko et al. 2020, and Shen et al. 2020. Note the paraphyletic relationships among genera:
The exact placement of Scaphirhynchus varies depending on the study and the methods used, with some placing it within the second most basal clade comprising primarily Pacific species (shown above), whereas others place it in its own clade that is more derived than the secondmost basal clade but less derived than the most derived Atlantic and Central Asian clade. No studies have yet delineated a relationship between it and Pseudoscaphirhynchus. In addition, the exact relationships of the members of the most derived, primarily Atlantic clade vary, although most analyses at least find all the species in it to form a monophyletic clade. The placement of A. sinensis also varies by the study, with some placing it as the only Pacific member of the otherwise Atlantic based most derived clade, whereas others place it with the rest of the Pacific sturgeons as a sister to A. dabryanus. in the rivers that flow into the Black, Azov, and Caspian Seas (Danube, Dnepr, Volga, Ural and Don); the north flowing rivers of Russia that feed the Arctic Ocean (Ob, Yenisei, Lena, Kolyma); in the rivers of Central Asia (Amu Darya and Syr Darya) and Lake Baikal. In the Pacific Ocean, they are found in the Amur River along the Russian Chinese border, on Sakhalin Island, and some rivers in northeast China. Most species are at least partially anadromous, spawning in fresh water and feeding in nutrient rich, brackish waters of estuaries or undergoing significant migrations along coastlines. However, some species have evolved purely freshwater existences, such as the lake sturgeon (Acipenser fulvescens) and the Baikal sturgeon (A. baerii baicalensis), or have been forced into them by human or natural impoundment of their native rivers, as in the case of some subpopulations of white sturgeon (A. transmontanus) in the Columbia River and Siberian sturgeon (A. baerii) in the Ob basin. Physical characteristics
Sturgeons retain several primitive characteristics from the bony fishes. Along with other members of the subclass Chondrostei, they are unique among bony fishes because their skeletons are almost entirely cartilaginous. To maintain structure, sturgeons are one of few organisms to retain a post embryonic notochord that acts like a soft spine running through the body. Notably, however, the cartilagineous skeleton is not a primitive character, but a derived one; sturgeon ancestors had bony skeletons. They also lack vertebral centra, and are partially covered with five lateral rows of scutes rather than scales. They also have four barbels—sensory organs that precede their wide, toothless mouths. They navigate their riverine habitats traveling just off the bottom with their barbels dragging along gravel, or murky substrate. Sturgeon are recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes. The skeletal support for the paired fins of ray finned fish is inside the body wall, although the ray like structures in the webbing of the fins can be seen externally. Sturgeons are among the largest fish: some beluga (Huso huso) in the Caspian Sea reportedly attain over and while for kaluga (H. dauricus) in the Amur River, similar lengths and over weights have been reported. They are also among the longest lived of the fishes, some living well over 100 years and attaining sexual maturity at 20 years or more. The combination of slow growth and reproductive rates and the extremely high value placed on mature, egg bearing females make sturgeon particularly vulnerable to overfishing. Sturgeons are polyploid; some species have four, eight, or 16 sets of chromosomes. Life cycle
Sturgeons are long lived, late maturing fishes. Their average lifespan is 50 to 60 years, and their first spawn does not occur until they are around 15 to 20 years old. Sturgeons are broadcast spawners, and do not spawn every year because they require specific conditions. Those requirements may or may not be met every year due to varying environmental conditions, such as the proper photoperiod in spring, clear water with shallow rock or gravel substrate, where the eggs can adhere, and proper water temperature and flow for oxygenation of the eggs. A single female may release 100,000 to 3 million eggs, but not all will be fertilized. The fertilized eggs become sticky and adhere to the bottom substrate upon contact. Eight to 15 days are needed for the embryos to mature into larval fish. During that time, they are dependent on their yolk sacs for nourishment. River currents carry the larvae downstream into backwater areas, such as oxbows and sloughs, where the free swimming fry spend their first year feeding on insect larvae and crustacea. During their first year of growth, they reach in length and migrate back into the swift flowing currents in the main stem river. Behavior
Sturgeons are primarily benthic feeders, with a diet of shellfish, crustaceans, and small fish. Exceptionally, both Huso'' species, the white sturgeon and the pallid sturgeon feed primarily on other fish as adults. They feed by extending their siphon like mouths to suck food from the benthos. Having no teeth, they are unable to seize prey, though larger individuals and more predatory species can swallow very large prey items, including whole salmon. Sturgeons feed non visually. They are believed to use a combination of sensors, including olfactory, tactile, and chemosensory cues detected by the four barbels, and electroreception using their ampullae of Lorenzini. The electroreceptors are thought to be used in various behaviors such as feeding, mating and migration. Many sturgeons leap completely out of the water, usually making a loud splash which can be heard half a mile away on the surface and probably further under water. Why they do this is not known, but suggested functions include group communication to maintain group cohesion, catching airborne prey, courtship display, or to help shed eggs during spawning. Other plausible explanations include escape from predators, shedding parasites, or to gulp or expel air. Another explanation is that it "simply feels good". in 2015, a 5 year old girl was fatally injured after a sturgeon leapt from the Suwannee River and struck her.
Automatic taxobox
| name = Sturgeon
| image = Acipenser oxyrhynchus (edit). png
| image caption = Atlantic sturgeon(Acipenser oxyrinchus oxyrinchus)
| fossil range =
| taxon = Acipenseridae
| authority = Bonaparte, 1831
| subdivision ranks = Genera
| subdivision =
†Boreiosturion
†Protoscaphirhynchus
†Engdahlichthys
†Anchiacipenser
†Priscosturion
Acipenser (paraphyletic)
Huso
ScaphirhynchusPseudoscaphirhynchus
Sturgeon (from Old English styrġa ultimately from Proto Indo European *str̥(Hx)yón ) is the common name for the 28 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early Jurassic period, some 174 to 201 million years ago. They are one of two living families of the Acipenseriformes alongside paddlefish (Polyodontidae). The family is grouped into four genera: Acipenser (which is paraphyletic, containing many distantly related sturgeon species), Huso, Scaphirhynchus, and Pseudoscaphirhynchus. Two species (A. naccarii and A. dabryanus) may be extinct in the wild, and one (P. fedtschenkoi) may be entirely extinct. Sturgeons are native to subtropical, temperate and sub Arctic rivers, lakes and coastlines of Eurasia and North America. A Maastrichtian age fossil found in Morocco shows that they also once lived in Africa. Sturgeons are long lived, late maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle like body that is smooth skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging in length. The largest sturgeon on record was a beluga female captured in the Volga Delta in 1827, measuring long and weighing Most sturgeons are anadromous bottom feeders, migrating upstream to spawn but spending most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. Several species of sturgeon are harvested for their roe, which is processed into the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction. Evolution
Fossil history
Acipenseriform fishes appeared in the fossil record some 174 to 201 million years ago, during the Early Jurassic, making them some of the earliest extant actinopterygian fishes. True sturgeons appear in the fossil record during the Upper Cretaceous, with amongst the oldest known remains being a partial skull from the Cenomanian (100–94 million years ago) of Alberta, Canada. In that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils. This is explained in part by the long generation interval, tolerance for wide ranges of temperature and salinity, lack of predators due to size and bony plated armor, or scutes, and the abundance of prey items in the benthic environment. They do, however, still share several primitive characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements, and unique jaw suspension. Phylogeny and taxonomy
Despite the existence of a fossil record, full classification and phylogeny of the sturgeon species has been difficult to determine, in part due to the high individual and ontogenic variation, including geographical clines in certain features, such as rostrum shape, number of scutes, and body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. While ray finned fishes (Actinopterygii) have a long evolutionary history culminating in the most familiar fishes, past adaptive evolutionary radiations have left only a few survivors, such as sturgeons and gars. The wide range of the acipenserids and their endangered status have made collection of systematic materials difficult. The factors have led researchers in the past to identify over 40 additional species that were rejected by later scientists. Whether the species in the Acipenser and Huso genera are monophyletic (descended from one ancestor) or paraphyletic (descended from many ancestors) is still unclear, though the morphologically motivated division between these two genera clearly is not supported by the genetic evidence. An effort is ongoing to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques. The phylogeny of Acipenseridae, as in the cladogram, shows that they evolved from the bony fishes. Approximate dates are from Near et al., 2012. However, multiple recent studies have recovered this arrangement as paraphyletic, instead finding A. oxyrhinchus and A. sturio to form the most basal clade among sturgeons, and all other species being in a separate clade, with the various other species of Acipenser, Scaphirhynchus, Pseudoscaphirhynchus, and Huso to have varying levels of relationship with one another. A potential taxonomy of Acipenseridae is shown here, based on Luo et al. 2019, Nedoluzhko et al. 2020, and Shen et al. 2020. Note the paraphyletic relationships among genera:
The exact placement of Scaphirhynchus varies depending on the study and the methods used, with some placing it within the second most basal clade comprising primarily Pacific species (shown above), whereas others place it in its own clade that is more derived than the secondmost basal clade but less derived than the most derived Atlantic and Central Asian clade. No studies have yet delineated a relationship between it and Pseudoscaphirhynchus. In addition, the exact relationships of the members of the most derived, primarily Atlantic clade vary, although most analyses at least find all the species in it to form a monophyletic clade. The placement of A. sinensis also varies by the study, with some placing it as the only Pacific member of the otherwise Atlantic based most derived clade, whereas others place it with the rest of the Pacific sturgeons as a sister to A. dabryanus. in the rivers that flow into the Black, Azov, and Caspian Seas (Danube, Dnepr, Volga, Ural and Don); the north flowing rivers of Russia that feed the Arctic Ocean (Ob, Yenisei, Lena, Kolyma); in the rivers of Central Asia (Amu Darya and Syr Darya) and Lake Baikal. In the Pacific Ocean, they are found in the Amur River along the Russian Chinese border, on Sakhalin Island, and some rivers in northeast China. Most species are at least partially anadromous, spawning in fresh water and feeding in nutrient rich, brackish waters of estuaries or undergoing significant migrations along coastlines. However, some species have evolved purely freshwater existences, such as the lake sturgeon (Acipenser fulvescens) and the Baikal sturgeon (A. baerii baicalensis), or have been forced into them by human or natural impoundment of their native rivers, as in the case of some subpopulations of white sturgeon (A. transmontanus) in the Columbia River and Siberian sturgeon (A. baerii) in the Ob basin. Physical characteristics
Sturgeons retain several primitive characteristics from the bony fishes. Along with other members of the subclass Chondrostei, they are unique among bony fishes because their skeletons are almost entirely cartilaginous. To maintain structure, sturgeons are one of few organisms to retain a post embryonic notochord that acts like a soft spine running through the body. Notably, however, the cartilagineous skeleton is not a primitive character, but a derived one; sturgeon ancestors had bony skeletons. They also lack vertebral centra, and are partially covered with five lateral rows of scutes rather than scales. They also have four barbels—sensory organs that precede their wide, toothless mouths. They navigate their riverine habitats traveling just off the bottom with their barbels dragging along gravel, or murky substrate. Sturgeon are recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes. The skeletal support for the paired fins of ray finned fish is inside the body wall, although the ray like structures in the webbing of the fins can be seen externally. Sturgeons are among the largest fish: some beluga (Huso huso) in the Caspian Sea reportedly attain over and while for kaluga (H. dauricus) in the Amur River, similar lengths and over weights have been reported. They are also among the longest lived of the fishes, some living well over 100 years and attaining sexual maturity at 20 years or more. The combination of slow growth and reproductive rates and the extremely high value placed on mature, egg bearing females make sturgeon particularly vulnerable to overfishing. Sturgeons are polyploid; some species have four, eight, or 16 sets of chromosomes. Life cycle
Sturgeons are long lived, late maturing fishes. Their average lifespan is 50 to 60 years, and their first spawn does not occur until they are around 15 to 20 years old. Sturgeons are broadcast spawners, and do not spawn every year because they require specific conditions. Those requirements may or may not be met every year due to varying environmental conditions, such as the proper photoperiod in spring, clear water with shallow rock or gravel substrate, where the eggs can adhere, and proper water temperature and flow for oxygenation of the eggs. A single female may release 100,000 to 3 million eggs, but not all will be fertilized. The fertilized eggs become sticky and adhere to the bottom substrate upon contact. Eight to 15 days are needed for the embryos to mature into larval fish. During that time, they are dependent on their yolk sacs for nourishment. River currents carry the larvae downstream into backwater areas, such as oxbows and sloughs, where the free swimming fry spend their first year feeding on insect larvae and crustacea. During their first year of growth, they reach in length and migrate back into the swift flowing currents in the main stem river. Behavior
Sturgeons are primarily benthic feeders, with a diet of shellfish, crustaceans, and small fish. Exceptionally, both Huso'' species, the white sturgeon and the pallid sturgeon feed primarily on other fish as adults. They feed by extending their siphon like mouths to suck food from the benthos. Having no teeth, they are unable to seize prey, though larger individuals and more predatory species can swallow very large prey items, including whole salmon. Sturgeons feed non visually. They are believed to use a combination of sensors, including olfactory, tactile, and chemosensory cues detected by the four barbels, and electroreception using their ampullae of Lorenzini. The electroreceptors are thought to be used in various behaviors such as feeding, mating and migration. Many sturgeons leap completely out of the water, usually making a loud splash which can be heard half a mile away on the surface and probably further under water. Why they do this is not known, but suggested functions include group communication to maintain group cohesion, catching airborne prey, courtship display, or to help shed eggs during spawning. Other plausible explanations include escape from predators, shedding parasites, or to gulp or expel air. Another explanation is that it "simply feels good". in 2015, a 5 year old girl was fatally injured after a sturgeon leapt from the Suwannee River and struck her.
Кавиар
В глобальном масштабе рыболовство осетровых имеет большую ценность, прежде всего как источник икры, но также и мяса. Несколько видов осетров добываются ради их икры, которая перерабатывается в деликатес – икру, и именно поэтому осетровые, производящие икру, являются одними из самых ценных и находящихся под угрозой исчезновения видов дикой природы. В XIX веке США были мировым лидером в производстве икры, контролируя 90% мировой торговли. Атлантический осетр когда-то процветал вдоль восточного побережья от Канады до Флориды. Их было так много в реке Гудзон, что их в шутку называли «албанским говяжьим мясом», а осетровую икру раздавали в местных барах в качестве закуски к пиву по 5 центов. Популяции белого осетра на западном побережье США одновременно сокращались из-за коммерческого вылова и антропогенного воздействия. В течение столетия обильные ранее популяции осетровых в США и Канаде резко сократились, а в некоторых районах были полностью истреблены из-за коммерческого перелова, загрязнения, антропогенного воздействия, потери среды обитания и строительства плотин, которые преграждали их исторические пути миграции к нерестилищам. К началу XX века коммерческое производство осетровой икры в США и Канаде прекратилось. Государственные и федеральные природоохранные ведомства США и Канады приняли нормативные меры защиты и начали природоохранные мероприятия, такие как федеральный мораторий США 1998 года, который закрыл весь коммерческий вылов атлантического осетра. Начиная с эмбарго США на Иран в 1979 году, браконьерство и контрабанда осетровой икры стали прибыльным, но незаконным и опасным бизнесом. Сотрудники Департамента рыбы и дикой природы штата Вашингтон (WDFW) разоблачили браконьерскую группировку, базировавшуюся в Ванкувере, штат Вашингтон. Браконьеры добыли 1,65 тонны икры почти из 2000 белых осетров, незаконно выловленных в реке Колумбия. Стоимость икры оценивалась примерно в 2 миллиона долларов. WDFW разоблачила еще одну группировку в 2003 году и провела тайную операцию в 2006–2007 годах, в результате которой 17 из 19 попыток были успешными. В ответ на обеспокоенность по поводу будущего осетровых и связанной с ними коммерческой продукции, с 1998 года международная торговля всеми видами осетровых регулируется в рамках CITES. Некоторые виды осетровых вымерли, а несколько находятся на грани исчезновения, включая китайского осетра, высоко ценимого осетра белугу и осетра Алабамы. Многие виды классифицируются как уязвимые или находящиеся под угрозой исчезновения, при этом наблюдается заметное сокращение популяций осетровых по мере роста спроса на икру. Данные МСОП показывают, что более 85% видов осетровых находятся под угрозой исчезновения, что делает их более уязвимыми, чем любая другая группа видов животных. Помимо глобальных усилий по восстановлению популяций, мониторинга популяций и среды обитания, а также различных других природоохранных мероприятий, осуществляемых национальными и штатными природоохранными ведомствами в соответствии с законодательством их стран, было создано несколько природоохранных организаций для содействия сохранению осетровых во всем мире. Одной из таких организаций в глобальном масштабе является Всемирное общество охраны осетровых (WSCS), основными задачами которого являются содействие «сохранению видов осетровых и восстановлению запасов осетровых во всем мире» и поддержка «обмена информацией между всеми заинтересованными в осетровых лицами». Североамериканское общество осетровых и лососевых (NASPS) и Gesellschaft zur Rettung des Störs e. V. являются аффилированными членами WSCS. WSCS играет важную роль в организации глобальных конференций, на которых ученые и исследователи могут обмениваться информацией и решать различные задачи сохранения, угрожающие будущему осетровых. Природоохранные мероприятия на местном уровне также играют важную роль в сохранении популяций осетровых, такие как Sturgeon For Tomorrow, основанная в 1977 году, состоящая из добровольцев и программы охраны осетровых для мониторинга известных нерестилищ. За эти годы организация значительно выросла и стала «крупнейшей общественной группой по защите осетровых в мире», расширившись за счет филиалов в других штатах, где обитают популяции осетровых. Другие проекты сосредоточены на конкретных местных проблемах, таких как проект «We Pass», направленный на поиск решения проблемы миграционного тупика, представленного «Железными воротами» в бассейне реки Дунай. Например, в настоящее время все анадромные дунайские осетры (все виды, за исключением преимущественно пресноводного стера) классифицируются как находящиеся под критической угрозой исчезновения или истребленные из верхнего и среднего течений реки Дунай выше плотин.
Globally, sturgeon fisheries are of great value, primarily as a source for caviar, but also for flesh. Several species of sturgeon are harvested for their roe which is processed into caviar—a delicacy, and the reason why caviar producing sturgeons are among the most valuable and endangered of all wildlife resources. During the 19th century, the US was the global leader in caviar production, having cornered 90% of the world's caviar trade. Atlantic sturgeon once thrived along the east coast from Canada down to Florida. They were in such abundance in the Hudson River that they were humorously called "Albany beef" and sturgeon eggs were given away at local bars as an accompaniment to 5¢ beer. White sturgeon populations along the US west coast declined simultaneously under the pressure of commercial fishing and human encroachment. Within the course of a century, the once abundant sturgeon fisheries in the US and Canada had drastically declined, and in some areas had been extirpated under the pressure of commercial overharvesting, pollution, human encroachment, habitat loss, and the damming of rivers that blocked their ancestral migration to spawning grounds. By the turn of the century, commercial production of sturgeon caviar in the US and Canada had come to an end. Regulatory protections and conservation efforts were put in place by state and federal resource agencies in the US and Canada, such as the 1998 US federal moratorium that closed all commercial fishing for Atlantic sturgeon. Beginning with the 1979 US embargo on Iran, poaching and smuggling sturgeon caviar was big business but an illegal and dangerous one. Officers with the Washington Department of Fish and Wildlife (WDFW) busted a poaching ring that was based in Vancouver, Washington. The poachers had harvested 1.65 tons of caviar from nearly 2,000 white sturgeon that were poached from the Columbia River. The caviar was estimated to be worth around $2 million. WDFW busted another ring in 2003, and conducted an undercover sting operation in 2006 2007 that resulted in 17 successful attempts out of a total of 19. In response to concerns over the future of sturgeons and associated commercial products, international trade for all species of sturgeons has been regulated under CITES since 1998. Some species of sturgeon are extinct, and several are on the verge of extinction, including the Chinese sturgeon, the highly prized beluga sturgeon, and the Alabama sturgeon. Many species are classified as threatened or endangered, with noticeable declines in sturgeon populations as the demand for caviar increases. IUCN data indicates that over 85% of sturgeon species are at risk of extinction, making them more critically endangered than any other group of animal species. In addition to global restocking efforts, the monitoring of populations and habitat, and various other conservation efforts by national and state resource agencies as applicable to their respective countries, several conservation organizations have been formed to assist in the preservation of sturgeons around the world. On a global scale, one such organization is the World Sturgeon Conservation Society (WSCS) whose primary objectives include fostering the "conservation of sturgeon species and restoration of sturgeon stocks world wide”, and supporting the "information exchange among all persons interested in sturgeons." The North American Sturgeon and Paddlefish Society (NASPS) and Gesellschaft zur Rettung des Störs e. V. are WSCS affiliates. WSCS has been instrumental in organizing global conferences where scientists and researchers can exchange information and address the various conservation challenges that threaten the future of sturgeons. Conservation efforts at the grass roots level are also instrumental in helping to preserve sturgeon populations, such as Sturgeon For Tomorrow which was founded in 1977, consists of volunteers and a sturgeon guarding program to monitor known spawning sites. The organization has grown exponentially over the years and has become "the largest citizen advocacy group for sturgeon in the world", and has expanded with affiliate chapters in other states that have sturgeon populations. Other projects focus on specific local issues, such as the We Pass project, seeking a solution to the migratory impasse represented by the Iron Gates in the Danube River Basin. For example, currently all anadromous Danube sturgeon (all species except the predominantly freshwater sterlet) are now classed as Critically Endangered or extirpated from the upper and middle reaches of the Danube River above the dams.
Другие применения
До 1800 года плавательные пузыри осетровых (в основном белуги из России) использовались как источник изогляна – формы коллагена, исторически применяемого для осветления вина и пива, как предшественник желатина и для консервации пергаментов. Еврейские законы кашрута, разрешающие употребление в пищу только рыбы, имеющей и чешую, и плавники, запрещают осетровых, поскольку у них ганоидная чешуя, а не разрешенные ктеноидная и циклоидная. Хотя все ортодоксальные течения запрещают употребление осетров, некоторые консервативные допускают это. Теологические споры о кошерности осетров восходят к реформаторам XIX века, таким как Арон Хорин, хотя их употребление уже было распространено в европейских еврейских общинах. В 1324 году король Эдуард II объявил осетров королевской рыбой. Формально, британская монархия до сих пор владеет всеми осетрами, китами и дельфинами, обитающими в водах вокруг Англии и Уэльса. По законам Соединенного Королевства, любой осетр, выловленный в пределах королевства, является личной собственностью монарха. Аналогичные законы, резервирующие осетров за королем, действовали в конце средневековой Дании. Археологический пример осетров в королевском контексте – это обломки датско-норвежского флагмана «Грибсхунден», затонувшего в июне 1495 года, когда король Ханс плыл из Копенгагена в Кальмар (Швеция) на дипломатический саммит. Археологи обнаружили на обломках бочку с разделанным осетром, вероятно, предназначенным для королевского стола во время пиров в Кальмаре. В геральдике осетр является символом на гербе святой Амальберги Темской.
Before 1800, swim bladders of sturgeon (primarily Beluga sturgeon from Russia) were used as a source of isinglass, a form of collagen used historically for the clarification of wine and beer, as a predecessor for gelatin, and to preserve parchments. The Jewish laws of kashrut, which only permit the consumption of fish with both scales and fins, forbids sturgeon, as they have ganoid scales instead of the permitted ctenoid and cycloid scales. While all Orthodox groups forbid the consumption of sturgeon, some Conservative groups do allow it. The theological debate over its kosher status can be traced back to such 19th century reformers as Aron Chorin, though its consumption was already common in European Jewish communities. Sturgeons were declared to be a royal fish under a statute dating back to 1324 by King Edward II of England. Technically, the British monarchy still owns all sturgeons, whales, and dolphins that inhabit the waters around England and Wales. Under the law of the United Kingdom, any sturgeons captured within the realm are personal property of the monarch. Similar laws reserving sturgeon for the king were enforced in late medieval Denmark. An archaeological example of sturgeon in a royal context comes from the wreck of the Danish Norwegian flagship, Gribshunden, which sank in June 1495 while King Hans sailed from Copenhagen to Kalmar, Sweden for a diplomatic summit. Archaeologists recovered from the wreck a cask containing a butchered sturgeon, probably intended for the king's table during feasts in Kalmar. In heraldry, a sturgeon is the symbol on the coat of arms for Saint Amalberga of Temse.