Tadpole

A tadpole or polliwog is the larva of a frog. It breathes water and lives in the water. Tadpoles hatch from small eggs.

Frog eggs are round and toad eggs are laid in long strings.  Like bird eggs, they have nutrients (food) inside them for the young animal to grow before it hatches.

Movement

Tadpoles swim by lateral undulation: their tails move side to side, not up and down.Zug G.R; Vitt L.J. & Caldwell J.P. 2001. Herpetology: an introductory biology of amphibians and reptiles. Academic Press.  

Food

Most types of tadpole eat only plants, for example algae on rocks. Some types of tadpole eat plants and animals, even other smaller tadpoles.

Metamorphosis

After some time, the tadpoles begin to grow legs: first the hind legs and then the front legs. Then they are called froglets.  Soon after, froglets grow lungs and begin to breathe air and lose their tails.  The tail disappears because the cells in the tail gently die.  Each tadpole's mouth changes from small to as wide as its head.  Its intestines become shorter.  They grow larger, and eventually become adults.

Species

How fast or slow the eggs hatch and how fast or slow the tadpole becomes a froglet is different in different frogs.  Some tadpoles take months to become frogs.  Some stay tadpoles all winter and do not become frogs until the next spring, or even three years later. Some frogs lay their eggs in bodies of water that are only there in the spring and dry up in the summer, so the tadpoles must become frogs in only a few weeks.

References

Category:Frogs
Category:Toads
Category:Developmental biology