Кіріспе
Ray finned fish Автоматты 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 (парафилетикалық)
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.
Ащылық (көне ағылшын тілінен styrġa, түп нұсқасы прото-индоевропалық *str̥(Hx)yón) – Acipenseridae тұқымдасына жататын 28 балық түрінің жалпы атауы. Ең ерте кездескен ащылық қазбалары кеш кретация кезеңіне жатады және олар ертедегі аципенсериформды балықтардың ұрпақтары болып табылады, олар ерте юра кезеңінен, шамамен 174-201 миллион жыл бұрын пайда болған. Олар Acipenseriformes тобының екі тірі отбасының бірі, paddlefish (Polyodontidae) олармен бірге. Отбасы төрт тұқымдасқа бөлінеді: Acipenser (парафилетикалық, көптеген алыс туысқан ащылық түрлері бар), Huso, Scaphirhynchus және Pseudoscaphirhynchus. Екі түрі (A. naccarii және A. dabryanus) жабайы табиғатта жойылып кеткен болуы мүмкін, ал біреуі (P. fedtschenkoi) толығымен жойылып кеткен болуы мүмкін. Ащылықтар Еуразия мен Солтүстік Американың субтропиктік, қоңыржай және субарктикалық өзендерінде, көлдерінде және жағалауларында мекендейді. Мароккода табылған мастрихт кезеңіне жататын қазбалар олардың Африкада да өмір сүргенін көрсетеді. Ащылықтар ұзақ өмір сүретін, кеш пісетін балықтар, олардың ерекше сипаттамалары бар, мысалы, акулаларға ұқсас гетероцеркальды құйрықтық қанаты, және тегіс терілі, қабықсыз, скот деп аталатын сүйекті пластиналардың бес қатарлы қатарымен жабық ұзын, орау тәрізді денесі бар. Бірнеше түрі өте үлкен, әдетте ұзындығы әртүрлі болуы мүмкін. Ең үлкен ащылық 1827 жылы Волга дельтасында ұсталған белұға анасы болды, оның ұзындығы және салмағы шамамен тең. Көптеген ащылықтар анадромустық түбіндегі жемшілер, шаруашылық үшін өзенге көшіп барады, бірақ өмірінің көп бөлігін өзен дельталарында және эстуарияларда жем іздеумен өткізеді. Кейбір түрлер тек тұщы су ортасында өмір сүреді, ал басқалары негізінен жағалау маңындағы теңіз ортасында өмір сүреді және ашық мұхитқа шығады. Ащылықтың бірнеше түрі олардың уылдырығы үшін ауланады, ол сәнді тағам – икраға өңделеді. Бұл түрлердің көпшілігін құрып кету қаупі төнген жағдайға жеткізген, шамадан тыс пайдалануға әкелді, басқа да қорғау қауіптерімен бірге.
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.
Қазбалар тарихы
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.
Аципенсериформды балықтар 174-201 миллион жыл бұрын, ерте юра кезеңінде пайда болды, бұл оларды ең ертедегі актиноптеригиан балықтарының біріне айналдырды. Шынайы ащылықтар жоғарғы кретация кезеңіндегі қазбалар жазбасында пайда болады, ең көне белгілі қалдықтардың бірі - Канаданың Альберта штатындағы сеноман (100-94 миллион жыл бұрын) кезеңіне жатқан жартылай бас сүйегі. Осы уақыт аралығында ащылықтар өте аз морфологиялық өзгеріске ұшырады, бұл олардың эволюциясы өте баяу болғанын көрсетеді және оларды тірі қазбалар ретінде бейресми мәртебеге ие етеді. Бұл ұзақ буындық аралықпен, температура мен тұздылықтың кең диапазонына төзімділікпен, өлшемі мен сүйекті пластиналы бронь немесе шұңқырлар, сондай-ақ бентологиялық ортада олжаның мол болуынан туындайды. Алайда, олар әлі де бірнеше бастапқы сипаттамаларды бөліседі, мысалы, гетероцеркальды құйрық, азайтылған қабықшалар, сүйекті элементтерді қолдаудан гөрі көбірек қанатты сәулелер және бірегей жақ сүйектері.
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.
Филогенезия және 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.
Қазбалардың бар екендігіне қарамастан, ащылық түрлерінің толық жіктелуі мен филогенезиясын анықтау қиын болды, бұл бөлігінде жоғары жеке және онтогендік өзгеріске байланысты, оның ішінде белгілі бір ерекшеліктердің географиялық клайндары, мысалы, рострамның пішіні, қабықшалардың саны және дене ұзындығы. Тағы бір алаңдатушы фактор - бұл әр түрлі тұқымдарға бөлінген түрлер арасында да, өсімдік көбеюі мүмкін будандар өндіруге арналған ащылықтардың ерекше қабілеті. Жаңбырлы қанатты балықтардың (Actinopterygii) ұзақ эволюциялық тарихы бар, ең танымал балықтарға айналған, өткен адаптивті эволюциялық сәулеленулер тек бірнеше тірі қалған, мысалы, ащылықтар мен гары. Аципенсеридтердің кең ауқымы мен олардың құрып кету қаупі төнгендігі жүйелі материалдарды жинауды қиындатты. Осы факторлар зерттеушілерді кейіннен ғалымдар жоққа шығарған 40-тан астам түрлерді анықтауға итермеледі. Acipenser және Huso тұқымдарының түрлері монофилетикалық (бір ата-бабадан тараған) немесе парафилетикалық (көп ата-бабадан тараған) екені әлі күнге дейін анық емес, бірақ бұл екі тұқым арасындағы морфологиялық негізделген бөліну генетикалық дәлелдермен расталмайды. Таксономиялық шатасуды шешу үшін жүйелі деректер мен молекулалық техникаларды біріктіру жұмысы жалғастырылуда. Acipenseridae филогенезиясы, кладограммада көрсетілгендей, сүйекті балықтардан пайда болғанын көрсетеді. Шамамен мерзімдер Near et al., 2012 ж. еңбектерінен алынған. Алайда, соңғы зерттеулердің көптеген нәтижелері бұл реттелуді парафилетикалық деп тапты, орнына A. oxyrhinchus және A. sturio ащылықтар арасындағы ең төменгі кладаны құрайды және барлық басқа түрлер жеке кладада болады, Acipenser, Scaphirhynchus, Pseudoscaphirhynchus және Huso түрлерінің әртүрлі деңгейдегі қарым-қатынасы бар. Acipenseridae-нің ықтимал таксономиясы Luo et al. 2019, Nedoluzhko et al. 2020 және Shen et al. 2020 ж. еңбектеріне негізделген. Тұқымдар арасындағы парафилетикалық қарым-қатынастарға назар аударыңыз:
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.
Scaphirhynchus-тың нақты орналасуы зерттеуге және қолданылған әдістерге байланысты өзгереді, кейбіреулері оны негізінен Тыныш мұхиты түрлерін қамтитын екінші төменгі кладаның ішіне қойса, ал басқалары оны екінші төменгі клададан артық, бірақ ең артық Атлант және Орталық Азия кладасынан кем дамыған жеке кладаға қояды. Оның Pseudoscaphirhynchus-пен қарым-қатынасы әлі анықталған жоқ. Сонымен қатар, ең артық, негізінен Атлант кладасының мүшелерінің нақты қарым-қатынасы әртүрлі, бірақ көптеген талдаулар олардың барлығын монофилетикалық клада құрайтынын анықтады. A. sinensis-тің орналасуы да зерттеуге байланысты өзгереді, кейбіреулері оны басқа Тыныш мұхиты ащылықтарымен салыстырғанда, әйтпесе Атлант негізіндегі ең артық кладаның жалғыз Тыныш мұхиты мүшесі деп санайды. Қара, Азов және Каспий теңіздеріне құятын өзендерде (Дунай, Днепр, Еділ, Орал және Дон); Арктика мұхитын қоректендіретін Ресейдің солтүстік ағысы бар өзендерде (Обь, Енисей, Лена, Колыма); Орталық Азия өзендерінде (Амудария және Сырдария) және Байкал көлінде. Тыныш мұхитында олар Ресей-Қытай шекарасындағы Амур өзенінде, Сахалин аралында және солтүстік-шығыс Қытайдағы кейбір өзендерде табылған. Көптеген түрлер кемінде жартылай анадромустық, тұщы суда шаруашылық жасайды және эстуариялардың қоректік заттарға толы тұзды суларында жем іздейді немесе жағалау бойындағы маңызды көші-қондар жасайды. Алайда, кейбір түрлер таза тұщы су ортасында өмір сүреді, мысалы, көл ащылығы (Acipenser fulvescens) және Байкал ащылығы (A. baerii baicalensis), немесе олардың туған өзендерінің адам немесе табиғи тоғанға түсуіне байланысты, мысалы, Колумбия өзеніндегі ақ ащылықтың (A. transmontanus) кейбір популяцияларында және Обь бассейніндегі Сібір ащылығында (A. baerii).
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.
Физикалық сипаттамалары
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.
Ащылықтар сүйекті балықтардан бірнеше бастапқы сипаттамаларын сақтайды. Chondrostei подкласының басқа мүшелерімен бірге, олардың қаңқаларының көп бөлігі хрящевой болып табылады. Құрылымды сақтау үшін ащылықтар дене арқылы өтетін жұмсақ омыртқа ретінде әрекет ететін эмбриондық нотохорданы сақтайтын сирек организмдердің бірі болып табылады. Алайда, хрящевой қаңқа бастапқы сипаттама емес, туынды сипаттама екенін атап өту қажет; ащылықтардың ата-бабаларында сүйекті қаңқалар болған. Олар сонымен қатар омыртқа орталықтарына ие емес және ...
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.
Икра
Жаһандық деңгейде осетр балықтарының аулауы өте маңызды, негізінен икра және ет үшін. Осётр балықтарының бірнеше түрі икра алу үшін ауланады, ол икраға айналады – бұл деликатес, сондықтан икра өндіретін осетрлер барлық жабайы табиғаттың ең құнды және жойылып бара жатқан ресурстарының қатарында. 19 ғасырда АҚШ икра өндірісінде әлемдік көшбасшы болды, әлемдік икра саудасының 90% -ын қамтыды. Атлантикалық осетр бір кезде Канададан Флоридаға дейінгі шығыс жағалауда гүлденген. Олар Гудзон өзенінде соншалықты көп болды, олар әзіл-сықақпен «Албани сиыр еті» деп аталды, ал жергілікті барларда 5 центтік сыраға ілеспе ретінде осетр жұмыртқалары берілді. АҚШ-тың батыс жағалауындағы ақ осетрлердің саны коммерциялық балық аулау мен адамдардың қоныстануының салдарынан бірден төмендеді. Бір ғасыр ішінде АҚШ пен Канададағы бір кезде көп болған осетр балықтарының аулау көлемі күрт азайды, ал кейбір аймақтарда коммерциялық шамадан тыс аулау, ластану, адамдардың басып кіруі, тіршілік ортасының жоғалуы және олардың ата-бабаларының шағын жерлеріне көшіп кетуіне кедергі келтірген өзендерді бөгеулеу салдарынан жойылып кетті. Ғасырдың басында АҚШ пен Канадада осетр икрасын коммерциялық өндіру тоқтатылды. АҚШ пен Канаданың мемлекеттік және федералды ресурстар агенттіктері нормативтік қорғау және сақтау шараларын енгізді, мысалы, 1998 жылғы АҚШ федералды мораторийі Атлантикалық осетрге барлық коммерциялық балық аулауды тоқтатты. 1979 жылы АҚШ Иранға эмбарго салғаннан бастап, осетр икрасын браконьерлікпен аулау және контрабанда жасау үлкен, бірақ заңсыз және қауіпті бизнеске айналды. Вашингтон Балық және жабайы табиғат басқармасының (WDFW) қызметкерлері Ванкуверде орналасқан браконьерлік желіні жойды. Браконьерлер Колумбия өзенінен ауланған 2000 ақ осетрден 1,65 тонна икра жинаған. Оның құны шамамен 2 миллион долларға бағаланған. WDFW 2003 жылы тағы бір желіні жойды және 2006-2007 жылдары жасырын операция жүргізді, нәтижесінде 19 әрекеттің 17 сәтті аяқталды. Осётр және оған байланысты коммерциялық өнімдердің болашағы туралы алаңдаушылыққа жауап ретінде 1998 жылдан бастап барлық осетр түрлері үшін халықаралық сауда CITES аясында реттелді. Кейбір осетр түрлері жойылып кеткен, ал бірнешеуі жойылып кету қаупіне тап болды, соның ішінде қытай осетрі, өте бағалы белуга осетрі және Алабама осетрі. Көптеген түрлер қатерлі немесе жойылып бара жатқан түрлерге жатқызылады, икраға деген сұраныс артуымен осетр популяциясы айтарлықтай төмендеді. IUCN деректері бойынша, осетр түрлерінің 85% -тан астамы жойылып кету қаупі бар, бұл оларды жануарлардың басқа түрлеріне қарағанда өте қауіпті етеді. Әлемдік қоныстандыруға, популяция мен тіршілік ортасын бақылауға және ұлттық және мемлекеттік ресурстар агенттіктерінің әртүрлі басқа да сақтау шараларына қоса, әлемдегі осетрлерді сақтауға көмектесу үшін бірнеше сақтау ұйымдары құрылды. Әлемдік деңгейдегі мұндай ұйымдардың бірі – Дүниежүзілік осетрді сақтау қоғамы (WSCS), оның негізгі мақсаттары «осетр түрлерін сақтау және әлемдегі осетр қорларын қалпына келтіру» және «осетрге қызығушылық танытқан барлық адамдар арасындағы ақпарат алмасуды» қолдауды қамтиды. Солтүстік Американың осетр және паддл балық қоғамы (NASPS) және Gesellschaft zur Rettung des Störs e. V. WSCS филиалдары болып табылады. WSCS ғалымдар мен зерттеушілердің ақпарат алмасып, осетрлердің болашағына қауіп төндіретін әртүрлі сақтау мәселелерін шешу үшін әлемдік конференцияларды ұйымдастыруда маңызды рөл атқарады. Жергілікті деңгейдегі сақтау жұмыстары, сондай-ақ 1977 жылы құрылған Sturgeon For Tomorrow сияқты, еріктілер мен осетрді күзету бағдарламасын белгілі шағын жерлерді бақылау үшін құрастырады. Ұйым жылдар бойы экспоненциалды түрде өсіп, «дүниедегі ең ірі осетрді қорғаушы азаматтар тобы» болды және осетр популяциясы бар басқа штаттардағы филиалдармен кеңейді. Басқа жобалар жергілікті мәселелерге, мысалы, «Біздің өткел» жобасына, Дунай өзенінің алабындағы Темір қақпалар арқылы көші-қон мәселесін шешуді көздейді. Мысалы, қазіргі уақытта барлық анадромалық Дунай осетрлері (әдетте тұщы судағы осетрлерден басқа барлық түрлер) қазір қауіпті түрде жойылып бара жатқан немесе бөгеттердің үстіндегі Дунай өзенінің жоғарғы және орта ағысынан жойылған деп саналады.
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.
Басқа қолданыстар
1800 жылға дейін есек балықтарының (негізінен Ресейден алынған Белуга есегінің) жүзу қуыстары айсингластың көзі ретінде қолданылған. Айсинглас – шарап пен сыраны тазарту, желатиннің алғашқы нұсқасы ретінде және пергаменттерді сақтау үшін тарихи түрде пайдаланылған коллагеннің бір түрі. Яһудилердің кашрут заңдары қабыршақтары мен қанаттары бар балықты ғана жеуге рұқсат береді, сондықтан есек балықтарына тыйым салынған, себебі оларда рұқсат етілген ктеноид және циклоид қабыршақтарының орнына ганоид қабыршақтары бар. Барлық православиелік ағымдар есек балығын жеуге тыйым салса, кейбір консервативтік ағымдар рұқсат етеді. Оның кошер мәртебесі туралы теологиялық пікірталас 19 ғасырдағы Арон Хорин сияқты реформаторларға дейін жетеді, бірақ оның тұтынуы Еуропалық яһуди қауымдастықтарында бұрыннан кең таралған. 1324 жылы Англия королі Эдуард II шығарған заң бойынша есек балықтары «патшалық балық» деп жарияланды. Техникалық тұрғыдан алғанда, британ монархиясы Англия мен Уэльс суларында мекендейтін барлық есек балықтарына, киттерге және дельфиндерге иелік етеді. Ұлыбритания заңнамасына сәйкес, корольдік аумақта ұсталған кез келген есек балығы монархтың жеке меншігі болып табылады. Есек балықтарын корольге арнауға қатысты ұқсас заңдар ортағасырлық Данияда да қолданылған. Есек балығының патшалық контекстегі археологиялық мысалы 1495 жылдың маусымында Дания-Норвегияның флагманы «Грибшунден» кемесінің сүңгуінен табылды. Бұл кеме Дания королі Ханс Копенгагеннен Швецияның Кальмар қаласына дипломатиялық саммитқа бара жатқанда суға батқан. Археологтар кемеден корольдің тойларында дастарқанға дайындалған, тілінген есек балығы бар шарап шелектерін тапты. Геральдикада есек балығы Темзе қасиетті Амальберганың гербіндегі символ болып табылады.
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.