Ellen Beth Damsky, age 9, of Utica, New York, for her question:
How do clams get born?
There are dozens of different clams in the world. Some types enjoy life in the muddy banks of fresh water streams and lakes. Other prefer life in the sandy floors and beaches of the salty sea. Most clams care nothing at all for their young ones, but a few types do try to protect their helpless infants.
When you dig up a clam, you can expect to find more. Almost always he has friends and relatives close by, buried or half buried in the sand or mud. Sometimes they are crowded so close that they almost touch each other. These clams, of course, are grown¬ups. Some are males and some are females, the mamas and the papas. There is a right time of year to have children but strange to say, the mama and papa clams never date each other. If they never meet and go courting, it seems downright impossible for them to have children. But they do.
The shell of a clam actually is only a house. It is two sturdy shells. gripped together by a mighty muscle and it protects the clam from his hungry enemies. The living clam inside the shell is a very lazy fellow with a soft, boneless body. He opens his shells a crack to let in the water and the water brings in bits of floating food for him to digest. The water also brings oxygen which he breathes through his gills. Sometimes he bothers himself to dig a bit deeper, but most of the time he has nothing to do.
However, at the right time of year, mother nature orders a new generation of clams. The mother clam's body grows a batch of egg cells and the father clam's body grows a batch of cells called sperm. When these cells are ready, the parents spill them out to the water. The water is clouded with zillions of these tiny tiny clam cells. Lots of them pair off and join together, an egg cell from a female clam and a sperm from a male clam. Together they form a fertilized egg with all the know how to grow into a baby clam. But the watery world is a dangerous place, full of hungry creatures. Most of the cloudy cells and even most of the baby clams get gobbled up before they grow up.
A few lucky ones escape and sink to the bottom where they feed and enjoy life. After a while, each baby clam spins a fine thread to tie himself down. He dines on floating scraps of food and grows to be as wide as a pea. Then it is time to hide. He starts to bury himself in the wet sand or mud. And chances are, dozens of other little clams from the same brood are settling nearby. Their childhood is over and here they stay for the rest of their lives.
Most mama and papa clams do nothing to help their children or to teach them how to grow up, but certain clams who live in fresh water streams are better mothers. They do not spill their egg cells out into the water. Instead, they catch some of the sperm cells as they drift by. The egg cells and sperm cells pair together and the mother clam keeps the fertilized eggs in her gills. There they grow and develop into larva clams. It takes about 300 of them to measure one inch. At last mama sends them outside her shells, out to cope with life in their watery world.