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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.
Most amphibians begin their lives as aquatic animals which are unable to live on dry land, often being dubbed as tadpoles. To reach adulthood , they go through a process called metamorphosis , in which they lose their gills and start living on land.
A dragonfly in its final moult, undergoing metamorphosis, it begins transforming from its nymph form to an adult. Metamorphosis is a biological process by which an animal physically develops including birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. [1]
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 ).
In amphibians there are salvary glands on the tongue, which in frogs produce what is called a two-phase viscoelastic fluid. When exposed to pressure, like when the tongue is wrapping around a prey, it becomes runny and covers the prey's body. As the pressure drops, it returns to a thick and elastic state, which gives the tongue an extra grip. [75]
Gosner stage 31 tadpole of Nidirana leishanensis. (A) Dorsal view. (B) Lateral view. (C) Ventral view. (D) Mouth structure. [1]Gosner stage is a generalized system of describing stages of embryonal and larval development in anurans (frogs and toads).
Unlike normal amphibians post-transformation, the skin does not have Leydig nor mucosal cells. [4] Induction of metamorphosis via thyroxine shortens the lifespan of the salamander to 5 months from the start of metamorphosis, while non-induced lifespans only last 48 days on average.
The best known representatives of taxa that exhibit some kind of the ontogenetic niche shift are fish (e.g. migration of so-called diadromous fish between saltwater and freshwater for purpose of breeding [2]), insects (e.g. metamorphosis between different life stages; such as larva, pupa and imago [2]) and amphibians (e.g. metamorphosis from ...