Frances Mosley, age 10, of Shreveport, Louisiana, for his question:
How can you tell a lizard from a salamander?
You might mistake a salamander and a small lizard for brothers. But they are not even cousins. In fact, they are so different that scientists place them in two separate animal classes. You can detect two different features, just by counting their toes and touching their skins. You also might notice that the lizard dislikes moisture. But the salamander can survive under water. This is because his special skin can breathe dissolved oxygen.
The small lizard has ten tiny fingers and ten tiny toes unless he has lost one or more in an accident. Chances are, this salamander has only four little fingers on each hand. Their skins do not look or even feel the same. The lizard wears a dry scaly skin. The salamander's skin is rough and slightly bumpy. When you gently touch it, it feels cool and moist.
An animal has to take great care of his skin, if he wishes to stay alive and healthy. This is so important that the lizard and the salamander must live different lives to protect their different skins. The lizard's tough dry skin thrives in warm dry air. He keeps away from damp corners and loves to spend a lazy afternoon sunbathing on a warm rock. The salamander cannot let his moist skin get dry, or he would perish. Its bumpy surface is riddled with tiny glands that ooze a moist substance called mucous. And he needs extra moisture to keep it damp all the time. So he scuttles away from the bright sunny air and hides himself in moist, shady corners. Just to be on the safe side, he prefers to live near the water, where he can take a daily dip in his private pool.
Their family lives also prove that the lizard and salamander are not related to each other. Mrs. Lizard lays a batch of round, soft shelled eggs, usually in loose, sandy soil. Then she deserts them and the sun keeps them warn while they get ready to hatch. The newborn babies look like small copies of their mother. The little smarties already know just what lizards must do to cope with life.
Mrs. Salamander strings her little round black eggs in blobs of jelly. She may lay them in her pool or in a shady tuft of grass if it stays drenched with dew.
The newborn babies are wriggly tadpoles with gills to take oxygen from the water. They cannot breathe air until later in life, when they grow lungs to replace their fishy gills. Then they live in moist, shady places on the land.
The lizard belongs to the great class of reptiles. His family goes back to the mighty dinosaurs, who ruled the world for 100 million years. The salamander belongs in the class of amphibians animals that belong to both land and water. His ancestors were the first backboned animals that left the sea, about 350 million years ago. But their special skins still need moisture and baby tadpoles must live in the water.