Portal:Amphibians
The Amphibian Portal
Amphibians are ectothermic, anamniotic, four-limbed vertebrate animals that constitute the class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all tetrapods excluding the amniotes (tetrapods with an amniotic membrane, such as modern reptiles, birds and mammals). All extant (living) amphibians belong to the monophyletic subclass Lissamphibia, with three living orders: Anura (frogs and toads), Urodela (salamanders), and Gymnophiona (caecilians). Evolved to be mostly semiaquatic, amphibians have adapted to inhabit a wide variety of habitats, with most species living in freshwater, wetland or terrestrial ecosystems (such as riparian woodland, fossorial and even arboreal habitats). Their life cycle typically starts out as aquatic larvae with gills known as tadpoles, but some species have developed behavioural adaptations to bypass this.
Young amphibians generally undergo metamorphosis from an aquatic larval form with gills to an air-breathing adult form with lungs. Amphibians use their skin as a secondary respiratory interface and some small terrestrial salamanders and frogs lack lungs and rely entirely on their skin. They are superficially similar to reptiles like lizards, but unlike reptiles and other amniotes, require access to water bodies to breed. With their complex reproductive needs and permeable skins, amphibians are often ecological indicators to habitat conditions; in recent decades there has been a dramatic decline in amphibian populations for many species around the globe.
The earliest amphibians evolved in the Devonian period from tetrapodomorph sarcopterygians (lobe-finned fish with articulated limb-like fins) that evolved primitive lungs, which were helpful in adapting to dry land. They diversified and became ecologically dominant during the Carboniferous and Permian periods, but were later displaced in terrestrial environments by early reptiles and basal synapsids (predecessors of mammals). The origin of modern lissamphibians, which first appeared during the Early Triassic, around 250 million years ago, has long been contentious. The most popular hypothesis is that they likely originated from temnospondyls, the most diverse group of prehistoric amphibians, during the Permian period. Another hypothesis is that they emerged from lepospondys. A fourth group of lissamphibians, the Albanerpetontidae, became extinct around 2 million years ago. (Full article...)
Selected frog article
Selected salamander article
Sirenidae, the sirens, are a family of neotenic aquatic salamanders. Family members have very small fore limbs and lack hind limbs altogether. In one species, the skeleton in their fore limbs is made of only cartilage. In contrast to most other salamanders, they have external gills bunched together on the neck in both larval and adult states. Sirens are found only in the Southeastern United States and northern Mexico.
Although they are primarily carnivorous, they are the only salamanders observed eating plant material. (Full article...)List of selected salamander articles
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Did you know? –
- ... that Lehmann's poison frog is not toxic in captivity because its poison derives from food it eats only in the wild?
- ... that the Brazil-nut poison frog (pictured) sometimes places its tadpoles in water-filled capsules that have fallen from the Brazil nut tree?
- ... that female gregarious slender salamanders often lay their eggs in communal nests?
- ... that toads found in Egypt around 1909 and identified as Degen's toad are now considered a separate species, the Nile Delta toad?
- ... that the recently named trematopid temnospondyl Fedexia was named after the shipping service FedEx, which owned the land where the holotype specimen was found?
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Caecilians (/sɪˈsɪliən/; New Latin for 'blind ones') are a group of limbless, vermiform (worm-shaped) or serpentine (snake-shaped) amphibians with small or sometimes nonexistent eyes. They mostly live hidden in soil or in streambeds, and this cryptic lifestyle renders caecilians among the least familiar amphibians. Modern caecilians live in the tropics of South and Central America, Africa, and southern Asia. Caecilians feed on small subterranean creatures such as earthworms. The body is cylindrical and often darkly coloured, and the skull is bullet-shaped and strongly built. Caecilian heads have several unique adaptations, including fused cranial and jaw bones, a two-part system of jaw muscles, and a chemosensory tentacle in front of the eye. The skin is slimy and bears ringlike markings or grooves and may contain scales.
Modern caecilians are a clade, the order Gymnophiona' /ˌdʒɪmnəˈfaɪənə/ (or Apoda /ˈæpədə/), one of the three living amphibian groups alongside Anura (frogs) and Urodela (salamanders). Gymnophiona is a crown group, encompassing all modern caecilians and all descendants of their last common ancestor. There are more than 220 living species of caecilian classified in 10 families. Gymnophionomorpha is a recently coined name for the corresponding total group which includes Gymnophiona as well as a few extinct stem-group caecilians (extinct amphibians whose closest living relatives are caecilians but are not descended from any caecilian). Some palaeontologists have used the name Gymnophiona for the total group and the old name Apoda for the crown group'. However, Apoda has other even older uses, including as the name of a genus of Butterfly making its use potentially confusing and best avoided. 'Gymnophiona' derives from the Greek words γυμνος / gymnos (Ancient Greek for 'naked') and οφις / ophis (Ancient Greek for 'snake'), as the caecilians were originally thought to be related to snakes and to lack scales.
The study of caecilian evolution is complicated by their poor fossil record and specialized anatomy. Genetic evidence and some anatomical details (such as pedicellate teeth) support the idea that frogs, salamanders, and caecilians (collectively known as lissamphibians) are each others' closest relatives. Frogs and salamanders show many similarities to dissorophoids, a group of extinct amphibians in the order Temnospondyli. Caecilians are more controversial; many studies extend dissorophoid ancestry to caecilians. Some studies have instead argued that caecilians descend from extinct lepospondyl or stereospondyl amphibians, contradicting evidence for lissamphibian monophyly (common ancestry). Rare fossils of early gymnophionans such as Eocaecilia and Funcusvermis have helped to test the various conflicting hypotheses for the relationships between caecilians and other living and extinct amphibians. (Full article...)List of selected amphibian type articles
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Photo credit: Derek RamseyThe American Green Frog (Rana clamitans) is native to the eastern half of the United States and Canada. Green frogs live wherever there is shallow freshwater: ponds, road-side ditches, lakes, swamps, streams and brooks. The green frog is abundant wherever it occurs. -
Photo: Charles H. Smith, USFWSThe golden toad (Bufo periglenes) is an extinct species of true toad that was once abundant in a small region of high-altitude cloud-covered tropical forests, about 30 km2 (12 sq mi) in area, above the city of Monteverde, Costa Rica. The last reported sighting of a golden toad was on 15 May 1989. Its sudden extinction may have been caused by chytrid fungus and extensive habitat loss. -
The Blue Mountains Tree Frog (Litoria citropa) is a moderate-sized species of tree frog, up to about 60 mm (2.4 in) in length. It is native to coastal and highland areas of eastern Australia, especially in the Blue Mountains, hence its name. -
Photo: QuartlDendrobates azureus, commonly known as the blue poison dart frog or okopipi, is a poison dart frog found in the forests surrounded by the Sipaliwini Savanna in southern Suriname. Authorities have recently treated it as a variant of Dendrobates tinctorius rather than a distinct species as before. -
Photograph: Brian GratwickeThe Panamanian golden frog (Atelopus zeteki) is a rare species of toad endemic to Panama. First described by Emmett Reid Dunn in 1933, this species was found close to mountain streams on the eastern side of the Tabasará mountain range in Coclé and Panamá Provinces, but is now critically endangered and possibly extinct in the wild. -
Photograph credit: Charles James SharpThe marsh frog (Pelophylax ridibundus) is a species of amphibian native to Europe and parts of Asia. It is the largest type of frog in most of its range, growing to a snout-to-vent length of around 100 mm (4 in); tadpoles can reach up to 190 mm (7.5 in) in length, but this usually occurs in places with long winters where the tadpole has time to grow. Marsh frogs hibernate during the winter, either underwater or in burrows, and are able to use the Earth's magnetic field to locate breeding ponds. This marsh frog was photographed in Kampinos National Park, Poland. -
Photograph: Richard Bartz -
Photo: Benny TrappAn Italian tree frog (Hyla intermedia) with an inflated vocal sac. Vocal sacs, flexible membranes of skin possessed by most male frogs, are generally used to amplify mating or advertisement calls. However, some species in the family Rhinodermatidae may also use the sac to store or transport their tadpoles. -
Photo credit: LiquidGhoulThe New England Tree Frog (Litoria subglandulosa) is a species of frog native to the streams of the New England Tablelands, New South Wales, Australia. -
Photo credit: liquidGhoulNative to Australia, White's Tree Frog grows up to 10 centimetres in length and is a popular household pet. In captivity, they have an average lifespan of 16 years. Its skin secretions contain caerins, a group of peptides with antibacterial and antiviral properties. Other peptides have been found to destroy HIV without harming healthy T-cells. -
The white-lipped tree frog (Litoria infrafrenata) is the world's largest tree frog. This species is native to the rainforests of Northern Queensland, New Guinea, the Bismarck Islands and the Admiralty Islands. It can reach a length of over 13 cm (5 in), with females growing larger than males. The lower lip has a distinctive white stripe, giving this species its common name. -
Illustration credit: Ernst HaeckelA frog is an amphibian characterized by long hind legs, a short body, webbed digits, protruding eyes and the absence of a tail. Frogs are most noticeable through their call, which can be widely heard during the mating season. It is estimated that up to 20% of amphibian species may care for their young in one way or another, and there is a great diversity of parental behaviours. For example, frogs in the Gastrotheca genus (upper left) carry their eggs in a pouch, and females of the Eleutherodactylus lineatus species (center left) carry their young on their back. -
Photograph credit: Petar MiloševićThe agile frog (Rana dalmatina) is a species of true frog in the family Ranidae. Native to central and southern Europe, its brownish dappled colouring helps to conceal it among the leaf litter on the forest floor. This frog, about 5 cm (2.0 in) long, was photographed in the Golovec Forest in Slovenia. -
Photograph credit: RushenbRaorchestes parvulus is a small bush frog native to tropical southeastern Asia. Although the reproductive strategy of this species has not been studied, members of the family typically make a foam nest while mating in vegetation overhanging a stream. They create the foam by beating their legs, and the eggs are deposited into the nest and covered with seminal fluid before the foam hardens into a protective casing. When the eggs hatch, the young push their way out of the nest and fall into the water below.
This picture shows a male R. parvulus frog, photographed in Phu Kradueng National Park, Thailand, calling by inflating its vocal sac. -
Photograph: Benny TrappThe Albanian water frog (Pelophylax shqipericus) is a species of true frog in the family Ranidae. It is native to Albania and Montenegro, where it lives in aquatic environments. The frogs are medium-sized. Males sometimes bear a distinctive bright green stripe down the length of the backbone, but otherwise are green to light brown in overall colouring with large black or dark brown spots. Females are olive green or light brown in colour and also bear brown or black large spots. The species is endangered and known populations are currently in decline.
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Selected toad article
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Selected caecilian article
Siphonops is a genus of caecilians in the family Siphonopidae, found in South America. All species are known to occur within Brazil, however, only S. hardyi and S. leucoderus are endemic to it. The native ranges of the other two known species, S. annulatus and S. paulensis, extend outwards into the surrounding countries of Argentina, Bolivia, and Paraguay. S. annulatus's range extends even further, stretching into Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname, and Venezuela, and giving it perhaps the most widespread distribution of any single caecilian species.
Siphonops contains the following four species:
- Siphonops annulatus — ringed caecilian
- Siphonops hardyi — Hardy's caecilian
- Siphonops leucoderus — Salvador caecilian
- Siphonops paulensis — Boettger's caecilian, cutuchi (Full article...)
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