Бразилияның шағын бақалары: Brachycephalus туысы

Genus of amphibians

The saddleback toads (Brachycephalus) are a genus of tiny toads and frogs in the family Brachycephalidae in the order Anura, ranging from south Bahia to Santa Catarina in southeastern Brazil. At about or less in snout–to–vent length, the flea frogs are some of the smallest frogs in the world. They are mostly diurnal, feed on tiny invertebrates and breeding is by direct development, with eggs laid on land and hatching into young frogs (no tadpole stage). The majority of the Brachycephalus species have only been discovered in the 21st century. Most species have tiny ranges and are seriously threatened. The genus can be divided into two main subgroups: The pumpkin toadlets comprises most species in the genus. They have an overall toad like appearance and morphology, and they mostly walk (they are unable to jump far). The second group are the flea frogs or flea toads (B. didactylus, B. hermogenesi, B. pulex and B. sulfuratus) that have an appearance and morphology that is more like leptodactylid frogs, and they are better jumpers. The skin of the saddleback toads can be rugose (bumpy) or smooth. The flea frogs or flea toads are generally the smallest at in adults, but overlapping to some extent with the smallest species of pumpkin toadlets. and the largest like B. darkside and B. margaritatus at least Newly hatched saddleback toads are much smaller than the already tiny adults. For example, they are typically in B. ephippium, Within each species, there are often also some individual variations, especially in the details of their pattern. The flea frogs or flea toads (B. didactylus, B. hermogenesi, B. pulex and B. sulfuratus) are well camouflaged and overall brown, often with sections that are greyer or near black, and sometimes with a few poorly defined yellowish spots below. Two particularly dull coloured species, B. brunneus and B. curupira, are overall brown, It is unknown how certain Brachycephalus species attain the strong neurotoxins, but they are possibly absorbed from the small invertebrates they eat, as known from some poison dart frogs and mantella frogs,

At least two brightly coloured species, B. ephippium and B. pitanga, have bones that are fluorescent, which is visible through the skin of the toadlet when exposed to UV light. It was initially speculated that the fluorescent colour also is aposematic or that it is related to mate choice (species recognition or determining fitness of a potential partner), Brachycephalus are most often located by their call. In addition to advertising calls, there are aggressive calls directed towards other males when close. It is speculated that their calling is a vestigiality from the ancestral form of the genus, whereas their reduced hearing ability (they do have some hearing ability in frequencies outside their call) is a novel change in these species. Sounds make them more vulnerable to predators, but there has likely been little direct evolutionary pressure to lose it because of their toxicity. The female rolls them until they are covered in particles, making them almost indistinguishable from the soil where they have been laid, but it may also help to preserve their water content.

Relatively little is known about the feeding behavior of saddleback toads, but they will take a wide range of minute invertebrates. They are known to feed on insects (among others, ants, true bugs, beetles, grasshoppers and flies) and their larvae, springtails, mites, spiders, pseudoscorpions, millipedes, snails and isopods. Due to Brachycephalus' extremely small head and body size, vestibular systems in the genus are too small for dependable locomotion, and in turn the endolymph — which is regarded by Poiseuille's law — is not detected by sensory hairs and makes it difficult for individuals of Brachycephalus to sense changes in angular acceleration during a jump. For the same reason they are moving slowly when they walk. Because of the uncontrolled jumping and slow walking, they have evolved defense mechanisms such as toxicity and bony plates (osteoderms) as protection against predators.

multiple image | direction = horizontal | image1 = Sapo. Brachycephalus darkside.1400x8000617. jpg | image2 = Brachycephalus quiririensis. png | total width = 400 | footer = B. darkside (left) and B. quiririensis (right), two recently described species that, according to a review in 2019, are critically endangered Since then, many new species have been recognised and more data has become available for evaluating their conservation status. In a review in 2019 that included all species recognised up until then and used IUCN's definitions, 10 species were data deficient, 5 least concern, 10 vulnerable, 5 endangered and 6 critically endangered. The three flea frogs B. didactylus, B. hermogenesi and B. sulfuratus and the pumpkin toadlet B. ephippiumsi are relatively widespread in both distribution and altitude range (lowlands to about ), although it is possible that the last of these actually is a species complex.

Brachycephalus lacks a Bidder's organ, but were historically included in the true toad family Bufonidae, where one of the defining features is its presence. The pumpkin toadlets, which largely are restricted to highlands and foothills, can be further divided into two subgroups: the southern B. pernix subgroup (Paraná and Santa Catarina) and the northern B. ephippium subgroup (São Paulo and north). Among the pumpkin toadlets, colours alone are not a good indicator of phylogenetic relationships. For example, the brown B. curupira is closely related to the golden B. izecksohni and the brown B. brunneus is closely related to the golden B. leopardus, but these species pairs are more distant from each other. Starting in 1998, this changed dramatically. Since that year, there has been a couple of years at most between the description of new species and some years where several were described, peaking at eight species in 2015 alone.