Robert Miller, age 10, of Arroyo Grande, California, for his question:

How do clams multiply?

Clams are stodgy stay at homes who spend their lives buried or half buried in sand or mud. Their soft bodies are encased in hard shells that tend to shut them away from each other and the rest of the world. Flowing water serves oxygen and scraps of food through their partly opened shells. Surely dating among the clams is a problem and if you suspect that the lazy do nothings are, careless parents, you are correct.

Some clams make their homes along the banks of muddy rivers, by lake shores and muddy streams. They are the freshwater clams. Other clams live along the shallow shores of the tide tossed ocean. They are the saltwater clams. Where you find one clam, there are usually more of them close by.  In some clam beds, the little fellows are crowded side by side. There is no more room and each batch of babies must travel to find homes for themselves.

There are male and female clams, and a baby clam is formed from a cell from each parent. Anew generation of saltwater clams begins when the male sheds a cloud of tiny sperm cells into the water. The female clam sheds a cloud of egg cells. A sperm and egg cell must meet and fertilize before a neon clam can begin to form. In the first few hours, thousands of them pair off in the water and become tiny larvae. It takes about 300 of these midgets to measure one inch and most of them are quickly gobbled up by hungry fishes.

Those that escape sink to the floor. However, they soon must start traveling, for they must find a fish and fix themselves to his gills. There they live for a while, looking like tiny white beads. At last they drop down and settle themselves on the floor of the sea. Each one spins a find thread called a byssus to anchor himself. When he gets to be about as big as a pea, he starts to bury himself in the soggy sand.

Some freshwater clams take a little more care of their children. Papa sheds his cloud of sperm cells, but Mama keeps the egg cells safe in her body. Some of the sperm cells are carried by the water into her gills. They meet and fertilize the egg cells and stay under Mama's protection while they grow and develop. When the brood is ready, the mother clam sends thousands of little ones out into the water. They drift around for a while and finally settle. But only a very few of them escape their enemies, find a suitable home and grow to become adult parent clams.

A pair of parent clams spread enough cells for millions of eggs. But only a few succeed. Even the females that keep the fertilized eggs for a while cannot help them to survive in the water. The saltwater species cannot protect their eggs at all. The vast majority of eggs and baby clams fail to survive, but they are not wasted. They are devoured by fish and shellfish and become part of the great food chain that feeds all the countless creatures of the sea.