Welcome to You Ask Andy

Jimmy Rodgers, Age 14., of Newport News., Va.., for his question:

Is a crab hatched or born alive?

He hatches from a miniature egg, and far the first months of his risky life you would never guess that the little fellow is a baby crab. He is so unlike his crusty parents that scientists call ham by a different name. He is a larva crab, and he must live through still another stage Of development before he can qualify as a crab.

Crabs belong to the class Crustacea of the phylum Arthrpoda. This vast phylum of the jointed animals includes spiders, scorpions and teeming hordes Of insects. The crustaceans include shrimps and lobsters, barnacles and bouncy water fleas. They have been called the insects of the sea. Like the true insects of the land, all of the crustaceans lay eggs.

The life story of the crusty crab is very like the life story of many insects. He goes through a metamorphosis, a series of changes which transform him from One kind of animal to a different one. The female crab lays several hundred miniature eggs of rosy orange color. For a while she may carry her eggs on her stalky legs.

In about a week the eggs hatch and swim away. Fifty of the youngsters in a row measure an inch. Each little swimmer is half a Millimeter long, and his mother would never recognize him. Several spikes grow from his back, and his long, Jointed abdomen ends in a thorny tail. The bug eyed midget has no crabby pincers and no crabby legs.

The odd youngster is a crab larva called a zoea. With luck, he will survive in the hungry ocean and after a great many changes will. Become a real crab. He grows by molting or shedding his coat about once a week. After each molt, he looks a little more like a miniature crab. After five molts he has a set of miniature crab legs, but he still has a long body and his bulging eyes. He is neither a zoea nor a crab. At this stage of his development he is a megalops. After four more molts, the megalop emerges as a miniature crab. The metamorphosis is now complete, and he changes no more. He merely gets bigger each time he molts.

A crab goes through the tricky operation of molting now and again throughout his life. A leathery skin grows under the shell, and when all is ready the shell cracks across the top. Out squeezes a soft shelled crab. In a few days his new skin becomes a crusty shell, but meantime he has no protective armor. The soft shelled crab stays quietly hidden from his hungry foes.


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