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 lepospondyls. A fourth group of lissamphibians, the Albanerpetontidae, became extinct around 2 million years ago. (Full article...)
Selected frog article
Brevicipitidae or rain frogs is a small family of frogs found in eastern and southern Africa. As of 2020 contains 37 species in 5 genera. Formerly included as subfamily in Microhylidae (narrow-mouth frogs), phylogenetic research has indicated the brevicipitine frogs should be considered as a family with Hemisotidae (shovelnose frogs) as the most closely related sister taxon.
Most adult brevicipitine frogs are not easily seen as they spend extended periods of time in soil or leaf litter. However, some species might be partly arboreal at times. Many species show strong sexual size dimorphism, with females being much larger than males.
At least the frogs in Breviceps and Probreviceps genera breed by direct development, in which small froglets emerge from eggs without intervening aquatic tadpole phase. It is likely that the same applies to the other genera, too. Because male Breviceps frogs are smaller than their female counterparts, amplexus is not possible; however mating pairs glue themselves together using excretions from holocrine glands on the ventrum of the male and similar glands on the dorsum of the back of the female. The frogs lay small clutches of 13–56 fairly large eggs (4–8 mm diameter not including the protective capsule) in cover, often in burrows. With some species either male or female stays with eggs or close to the egg chamber, though the details and extent of brood care is poorly understood within Brevicipitidae as a whole. (Full article...)
Selected salamander article
Ambystomatidae is a family of salamanders belonging to the Suborder Salamandroidea in the class Amphibia. It contains two genera, Ambystoma (the mole salamanders) and Dicamptodon (the Pacific giant salamanders). Ambystoma contains 32 species and are distributed widely across North America, while Dicamptodon contains four species restricted to the Pacific Northwest. These salamanders are mostly terrestrial and eat invertebrates, although some species are known to eat smaller salamanders. They can be found throughout the US and some areas of Canada in damp forests or plains. This family contains some of the largest terrestrial salamanders in the world, the tiger salamander and the coastal giant salamander. Some species are toxic and can secrete poison from their bodies as protection against predators or infraspecific competition. Neoteny has been observed in several species in Ambystomatidae, and some of them like the axolotl live all of their lives under water in their larval stage. (Full article...)
List of selected salamander articles
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Did you know? –
- ... that the Early Permian microsaur Rhynchonkos (pictured) shares many similarities with Eocaecilia, and may be an ancestor of caecilians?
- ...that the Australian Giant burrowing frog does not croak, but rather hoots like an owl?
- ... that Woodhouse's toad (pictured) seems to be displacing the Arizona toad in central Arizona?
- ... that the call of the Sonoran green toad is said to resemble "the buzzer on an electric alarm clock"?
Selected amphibian type
A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (coming from the Ancient Greek ἀνούρα, literally 'without tail'). The oldest fossil "proto-frog" Triadobatrachus is known from the Early Triassic of Madagascar (250 million years ago), but molecular clock dating suggests their split from other amphibians may extend further back to the Permian, 265 million years ago. Frogs are widely distributed, ranging from the tropics to subarctic regions, but the greatest concentration of species diversity is in tropical rainforest. Frogs account for around 88% of extant amphibian species. They are also one of the five most diverse vertebrate orders. Warty frog species tend to be called toads, but the distinction between frogs and toads is informal, not from taxonomy or evolutionary history.
An adult frog has a stout body, protruding eyes, anteriorly-attached tongue, limbs folded underneath, and no tail (the tail of tailed frogs is an extension of the male cloaca). Frogs have glandular skin, with secretions ranging from distasteful to toxic. Their skin varies in colour from well-camouflaged dappled brown, grey and green to vivid patterns of bright red or yellow and black to show toxicity and ward off predators. Adult frogs live in fresh water and on dry land; some species are adapted for living underground or in trees.
Frogs typically lay their eggs in the water. The eggs hatch into aquatic larvae called tadpoles that have tails and internal gills. They have highly specialised rasping mouth parts suitable for herbivorous, omnivorous or planktivorous diets. The life cycle is completed when they metamorphose into adults. A few species deposit eggs on land or bypass the tadpole stage. Adult frogs generally have a carnivorous diet consisting of small invertebrates, but omnivorous species exist and a few feed on plant matter. Frog skin has a rich microbiome which is important to their health. Frogs are extremely efficient at converting what they eat into body mass. They are an important food source for predators and part of the food web dynamics of many of the world's ecosystems. The skin is semi-permeable, making them susceptible to dehydration, so they either live in moist places or have special adaptations to deal with dry habitats. Frogs produce a wide range of vocalisations, particularly in their breeding season, and exhibit many different kinds of complex behaviors to attract mates, to fend off predators and to generally survive. (Full article...)
List of selected amphibian type articles
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Selected images
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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. -
Photo credit: Patrick CoinA terrestrial subadult Eastern newt or red eft (Notophthalmus viridescens). Salamanders of the family Salamandridae with aquatic adult stages are called newts. Some newts, including the Eastern newt, have a juvenile terrestrial stage called the eft. The red eft has bright aposematic coloration to warn predators of its highly toxic skin. -
Photo credit: Carey James BalboaThe Red-eyed Tree Frog (Agalychnis callidryas) is a small-sized tree frog, reaching lengths of about 5 to 7 centimeters (3 inches), native to Neotropical rainforests in Central America. They are not poisonous and rely on camouflage to protect them. During the day, they remain motionless with their colorful parts hidden. Thus, they appear almost completely green, and well hidden among the foliage. -
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. -
Common toads in amplexusPhoto: Bernie KohlTwo common toads (Bufo bufo) in amplexus, a form of pseudocopulation found in amphibians and limulids. A male common toad grasps a female with his front legs as part of the mating process. Common toads stay in amplexus for several days. As the female lays a long, double string of small black eggs, the male fertilises them with his sperm; the gelatinous egg strings, which may contain 3000 to 6000 eggs and be 3 to 4.5 metres (10 to 15 ft) in length, are later tangled in plant stalks. -
A male Dendropsophus microcephalus frog, displaying its vocal sac—membranes of skin under the throat or on the corner of the mouth that distend to amplify its call. The species lives in moist areas in most of Central America and northern South America. -
Photograph: Brian GratwickeRabbs' fringe-limbed treefrog (Ecnomiohyla rabborum) is a large species of frog originally found in the forest canopies of central Panama. Only discovered in 2005, the species is thought to be extinct in the wild; only one specimen, a male at the Atlanta Botanical Garden, survives. -
Photo credit: LiquidGhoulThe Red-eyed Tree Frog (Litoria chloris) is a species of tree frog native to eastern Australia; ranging from north of Sydney to Proserpine in mid-northern Queensland. These frogs typically reach a size of 65 millimetres (2.6 in). Its skin secretions have been found to destroy HIV, without harming healthy T cells. -
Photograph credit: RushenbWallace's flying frog (Rhacophorus nigropalmatus) is a moss frog found in tropical southeastern Asia. It is named after the British naturalist Alfred R. Wallace, who collected the first known specimen of the species. It lives almost exclusively in trees, and when threatened, or in search of prey, will leap from a branch and splay its four webbed feet; the membranes between its toes and the loose skin flaps on its sides catch the air as it falls, helping it to glide. This individual was photographed in Khao Sok National Park, Thailand. -
Photograph: Richard Bartz -
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. -
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 credit: FroggydarbA specimen from the "hybrid zone" of the Leaf Green Tree Frog (Litoria phyllochroa) and the Southern Leaf Green Tree Frog (L. nudidigitus), showing physical characteristics of both species. These small stream-dwelling frogs (averaging only 40mm in length), are native to eastern Australia and occur together south of Sydney. The two species are differentiated only by distribution, call and slight differences in flank markings. -
Photograph: Benny TrappThe Iberian midwife toad (Alytes cisternasii) is a species of frog in the family Alytidae found in Portugal and western Spain. Its natural habitats are temperate forests and shrubland, Mediterranean-type shrubby vegetation, intermittent rivers and freshwater marshes, pastureland, and aquaculture ponds. The species is affected by habitat loss, and the IUCN lists it as being "Near Threatened". -
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.
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Selected toad article
Atelopus varius, the Costa Rican variable harlequin toad or clown frog, is a small Neotropical true toad from the family Bufonidae. Once ranging from Costa Rica to Panama, A. varius is now listed as critically endangered and has been reduced to a single remnant population near Quepos, Costa Rica (rediscovered in 2003), and has only relict populations in western Panama. Recent variation in air temperature, precipitation, stream flow patterns, and the subsequent spread of a pathogenic chytrid fungus (Batrachochytrium dendrobatidis) linked to global climate change have been the leading cause of decline for A. varius. A. zeteki has been considered a subspecies of A. varius, but is now generally considered a separate species.[page needed] (Full article...)
Selected caecilian article
Chikila fulleri, also known as the Kuttal caecilian, Fuller's caecilian, and Fuller's chikila, is a species of caecilian from South Asia. In 2012 it was reassigned to a newly erected family, Chikilidae. (Full article...)
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