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), 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.
The young generally undergo metamorphosis from larva with gills to an adult air-breathing form with lungs. Amphibians use their skin as a secondary respiratory surface 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 water bodies in which to breed. With their complex reproductive needs and permeable skins, amphibians are often ecological indicators; 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 sarcopterygian fish with lungs and bony-limbed fins, features that 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 (mammal predecessors). The origin of modern amphibians belonging to Lissamphibia, which first appeared during the Early Triassic, around 250 million years ago, has long been contentious. However the emerging consensus is that they likely originated from temnospondyls, the most diverse group of prehistoric amphibians, during the Permian period. (Full article...)
Selected frog article
The tailed frogs are two species of frogs in the genus Ascaphus, the only taxon in the family Ascaphidae /æˈskæfɪdiː/. The "tail" in the name is actually an extension of the male cloaca. The tail is one of two distinctive anatomical features adapting the species to life in fast-flowing streams. These are the only North American frog species that reproduce by internal fertilization. They are among the most primitive known families of frogs.
Its scientific name means 'without a spade', from the privative prefix a- and the Ancient Greek skaphís (σκαφίς, 'spade, shovel'), referring to the metatarsal spade, which these frogs do not have. (Full article...)Selected salamander article
Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All ten extant salamander families are grouped together under the order Urodela from the group Caudata. Salamander diversity is highest in eastern North America, especially in the Appalachian Mountains; most species are found in the Holarctic realm, with some species present in the Neotropical realm.
Salamanders never have more than four toes on their front legs and five on their rear legs, but some species have fewer digits and others lack hind limbs. Their permeable skin usually makes them reliant on habitats in or near water or other cool, damp places. Some salamander species are fully aquatic throughout their lives, some take to the water intermittently, and others are entirely terrestrial as adults.
This group of amphibians is capable of regenerating lost limbs as well as other damaged parts of their bodies. Researchers hope to reverse engineer the regenerative processes for potential human medical applications, such as brain and spinal cord injury treatment or preventing harmful scarring during heart surgery recovery. The remarkable ability of salamanders to regenerate is not just limited to limbs but extends to vital organs such as the heart, jaw, and parts of the spinal cord, showing their uniqueness compared to different types of vertebrates. This ability is most remarkable for occurring without any type of scarring. This has made salamanders an invaluable model organism in scientific research aimed at understanding and achieving regenerative processes for medical advancements in human and animal biology. (Full article...)List of selected salamander articles
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Did you know? –
- ... that the Pyrenean brook salamander sometimes lives entirely underground in caves?
- ... that Rhachitomi, a group of temnospondyl amphibians, was established as a clade in 2013?
- ... that the specific name of Tambachia trogallas, the type species of the trematopid temnospondyl Tambachia, refers to the Thuringian bratwurst that was frequently eaten by the describers of the species?
- ... that the female tree frog Aplastodiscus leucopygius inspects the underground nesting chamber prepared by the male before accepting his advances?
- ... that the Italian pool frog (pictured) has been introduced into the United Kingdom?
Selected amphibian type
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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Selected images
Selected toad article
Ansonia inthanon is a species of toad in the family Bufonidae.
A small stream toad, measuring only 22-26mm in length. Its natural habitat is near torrents in subtropical forest on sloping land. It is threatened by habitat loss for agriculture, use by medical research (although this is not a significant threat) and by the introduced American bullfrog. Though it is only known from Doi Inthanon National Park and Thongphaphum in Kanchanaburi Province, it is not rare in suitable habitat. The species was recently discovered in a third locality, Doi Suthep National Park in Chiang Mai Province, and may also exist in similar habitat in northern Thailand and adjacent Myanmar. (Full article...)Selected caecilian article
The Western Ghats in India are home to several species of caecilians (Gymnophiona).
Caecilians are legless, burrowing amphibians which mostly live in leaf litter, loose soil, under rocks and decaying logs. They are also found in agricultural fields and only surface during the monsoon. The body is elongated and smooth with a slimy skin. The smaller caecilians superficially resemble earthworms while the larger ones are often mistaken for snakes. However, they can be told apart from earthworms by the presence of eyes, teeth and skeleton and from snakes by the lack of scales on skin. The eyes in caecilians are not well developed which is most likely to be because of their burrowing life style. They are considered as rare which is apparently due to their subterranean habits. To see them one has to search carefully (usually by digging) and be at the right place and at the right time. There are few places where they are common, but, at least one species was reported to be abundant in agricultural fields in Kerala. The larger caecilians can resemble snakes, but their skin is smooth, not scaly. (Full article...)Need help?
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