Tadpole Life Cycle
A tadpole, or polliwog, is an early stage in the life cycle of a frog. With no form of defense from predators and its habitat, the tadpole is a vulnerable stage in a frog's life. From hatching from an egg to its final development into a frog, the tadpole goes through a metamorphosis.
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Spawn
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The first stage is the laying of an egg mass, called a spawn. The eggs are laid in or near water. As the female frog lays her eggs, the male will fertilize them. Some frog species remain around the eggs and protect them as they develop. Others will leave the egg mass to fend for itself.
Egg
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The life of a tadpole starts upon fertilization of the egg. The central yolk splits in two, then four, then eight and so on until a raspberry-colored embryo can be seen. As it develops, a baby tadpole can be seen moving around inside the egg. It usually takes up to 21 days from fertilization until the tadpole hatches from the egg. Some eggs won't hatch -- those that die will turn white or opaque.
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Tadpole
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A hatched tadpole has a black oval body and a black tail. As soon as it hatches it will eat the egg it was in. The tadpole can only breathe underwater with its small gills. It will often hang on to floating vegetation as it adjusts to life outside its egg. By its fourth week it will socialize with other tadpoles in small groups. Some tadpoles will not reach adulthood; they will be eaten by predators or die of disease.
Growing Tadpole
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Between 6 and 9 weeks old, the tadpole will start to develop legs. It will still have a tail and remain underwater using its gills to acquire oxygen. The tadpole will start to change its diet to a more carnivorous one, eating dead insects as well as plants. Stubs start to develop where its arms will grow, and its head takes on a more elongated shape. This is an important stage in a tadpole's life as it starts to take on the physical features of a frog.
Froglet
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At 3 months old the tadpole is now a miniature frog. It has arms, legs and a head that resemble an adult frog but it hasn't reached a fully grown frog's size. It will still have a tail, which will be lost when the froglet becomes an adult frog. The froglet will develop lungs, which enables it to live outside of water.
Frog
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The physical signs a froglet has become an adult frog is the loss of its tail. Its lungs are now fully formed. It takes approximately four months to reach this stage. At this point in its life, the frog has reached full maturity.
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References
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