From Encyclopedia Jr, free information reference for Kids
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For other uses, see Tadpole (disambiguation).
Tadpole of
Littlejohn's Tree Frog (Litoria littlejohni)
A tadpole (also known as a pollywog or polliwog) is a larval amphibian, the juvenile form of a frog, toad, newt, salamander, or caecilian.
In this stage it breathes by means of external or internal gills, is at first lacking legs, and has a fin-like tail with which it swims as most fish do, by lateral undulation. As a tadpole matures, it metamorphoses by gradually growing limbs and then (in the case of frogs and toads) absorbing its tail by apoptosis (controlled cell death). Tadpoles depend very much on clean water. Most tadpoles are herbivorous, subsisting on algae or other greens such as boiled lettuce in captivity. However, they are true omnivores, being able to adapt to a carnivorous life style as well. When kept under herbivorous conditions, the gut becomes long and spiral. Under carnivore conditions, the gut becomes shorter. In a few species, some tadpoles turn cannibalistic under harsh conditions and feed on other tadpoles living in the pond. As a tadpole develops it grows two back legs and then front legs. The tail is gradually absorbed into the body until it is just a stump. The tadpole's gills disappear as its lungs develop. When the tadpole has fully transformed into a frog it can leave the water in search of a mate. Most frogs stay in or around water after changing from their larval form.
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Embryos (and one tadpole) of the wrinkled frog (
Rana rugosa)
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