Tadpole
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A tadpole (also known as a pollywog or polliwog) is a larval amphibian, the first stage of a frog or toad.
Not uncommonly, during the tadpole stage of an amphibian's life cycle, the tadpole breathes by means of autonomous external or internal gills. They do not have arms or legs until later stages in their lives, and has dorsal or fin-like appendages tail with which it swims by lateral undulation, similar to most fish. As a poliwog (tadpole) matures, it metamorphoses by gradually growing limbs and then (in the case of frogs) outwardly absorbing its tail by apoptosis. Lungs develop around the time of leg development, and tadpoles late in development will often swim to the surface of the water to breath air. During the final stages of external metamorphosis, the tadpole's mouth must change from a small round mouth at the front of the head, to a large mouth the same width as the head. The intestine will shorten to accommodate the frog's carnivorous diet.
Most tadpoles are herbivorous, subsisting on algae and plants. Some species are omnivorous, eating detritus and, whenever available, other tadpoles.
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