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of Frogs |
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Frog eggs vary in size, color, and shape. A jellylike substance covers frog eggs, providing a protective coating. This jelly also differs from species to species. Some species of frogs lay several thousand eggs at time. But only a few of these eggs develop into adult frogs. Ducks, fish, insects, and other water creatures eat many of the eggs. Even if the eggs hatch, the tadpoles also face the danger of being eaten by larger water animals. In addition, the pond or strearn in which the eggs were laid sometimes dries up. As a result, the tadpoles die. After mating, in most species the eggs are left in the water where they will hatch within 3 to 25 days, depending on the species and the water temperature. Certain tropical frogs lay their eggs in rain water that collects among the leaves of plants or in holes in tree Other tropical species attach their eggs to the underside of leaves that grow over water. When the eggs hatch, the tadpoles fall into the water. Some tropical frogs lay their eggs on land. They lay them under logs or dead leaves. These frogs have no tadpole stage. A young frog hatches from the egg and begins life as a land animal. Tadpoles are not completely developed when they hatch. At first, the tadpole clings to some support in the water, using its mouth or a tiny sucker. A tadpole has no neck, and so its head and body look like one round form. The animal has a long tail and resembles a little fish. It breathes by means of gills, which are hidden by a covering of skin. A tadpole's form changes as the animal grows. The tail becomes larger and makes it possible for the animal to swim about to obtain food. Tadpoles eat plants and decaying animal matter. Some tadpoles eat frog eggs and other tadpoles. In time, the tadpole begins to grow legs. The hind legs appear first. Then the lungs begin to develop and the front legs appear. The digestive system changes, enabling the frog that develops to eat live animals. Just before its metamorphosis into a frog, the tadpole loses its gills. Finally, a tiny frog, still bearing a stump of a tail, emerges from the water. Eventually, the animal absorbs its tail and assumes its adult form. Some tadpoles are so small they can hardly be seen. But a fully developed bullfrog tadpole may measure 6 to 7 inches long. In most species, a tadpole changes into an adult within a few months. After a frog becomes an adult, it may take a few months to a few years before the animal is mature enough to breed. The green frog and the pickerel frog mature in about three years. Few species of frogs live longer than 6 to 8 years in the wild. Many are eaten by such enemies as bats, herons, raccoons, snakes, turtles, and fish.
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