Gerry Kimbrell, age 12, of Bixby, Oklahoma, for her question:

Does the crayfish build a nest?

The crayfish is a small freshwater cousin of the sea dwelling lobster. He prefers to do his foraging after dark. This means he must make plans to keep out of sight during the day. He may hide in the gravelly bottom or dig himself a smallish burrow in the muddy banks of his stream or pond. Or he may dig a burrow in the bottom and surround it with a turret. The female enters a sort of nesting burrow when she lays her eggs.

You may not notice them, but various crayfish lurk in most of our lakes, streams and boggy swamps. Sometimes they build fancy doorways that reveal their hideaways, especially when the floor of their stream is surfaced with sandy gravel. What you see looks like a camp of small muddy mounds. Actually, each mound is a turret of damp dirt packed around the entrance to a burrow.

Chances are, the crayfish lurks with his pincers and whiskery antennas poking out through his roof. Naturally he hopes to grab a small fish or some other passing swimmer. After dark, he crawls forth on his eight skinny walking legs to forage for greenery and whatever decaying material he can find.

Though the turret builders appear to live in communities, crayfish are not sociable creatures and often fight among themselves. Actually, the adult lives his own life and keeps more or less to himself. In most cases, he inhabits a separate hideaway in a submerged burrow ox in the mud just above the water level.

Building his burrow is no problem for he is well equipped with tools. His pincers and skinny' legs are encased in a crusty shell and his tail has a crusty fan shaped scooper. Though his burrow can be called a nest, he does not use it as a bedroom. When his watery world grows dark enough for safety, he walks forth on his skinny legs. If startled, he can swim backward like a darting arrow.

There is one occasion when the burrow becomes more of a nest. Crayfish mate in the fall when the male places his sticky milt onto the female's abdomen. She then retires to her burrow where she lays about a hundred of her own eggs. The fertilizer eggs are fixed onto the bristles of her swimmerets. There they remain through the winter.

The brood of baby crayfishes hatches in the spring    and each tiny creature looks like a mini copy of its parents. Their pale glassy shells are tinged with patches of pink. They crowd together, clinging to mother's swimmerets with their claws. Soon they leave home and as they grow, their tiny shells are molted for larger ones.

The crayfish shell is built of calcium chemicals extracted from the water    and building a larger shell is quite a problem. First the chalky minerals in the old shell are dissolved into the blood and rebuilt into the new shell below. Then the body swells up with extra water and the papery thin old shell is cast off. Extra calcium is added to harden the new shell and after six hours or so, the  job is finished.