Don Rubel, age 13, of Palatine, I11., for his question:
HOW DO OYSTERS REPRODUCE?
About 50 A.D., Romans in England would gather oysters during winter. After packing them carefully in ice and snow, they would ship them back to Rome. Later fishermen raised oysters in "farms" in the waters off the Italian coast. Today the same thing is being done in the United States where half of each year's oyster crop comes from undersea farms along the Atlantic Coast.
A female oyster may produce as many as 500 million eggs each year. The oyster will lay the eggs that are already fertilized by spraying them out into the water. The eggs are a yellowish material and are so tiny that a large mass of them will look very much like a splash of thick cream.
Young oysters, called spats, are hatched about 10 hours after the eggs are laid. Each spat is about as big as the mark made by a needle's point.
An oyster spat looks a bit like a toy top. He can swim by means of hairlike growths called cilia. The cilia beat the water like whips and push the oyster forward. By the time the spat is 24 hours old, shells begin to grow.
The first two weeks of an oyster's life are spent floating and swimming. During this time he develops a muscular ''foot'' that extends from his body. The foot disappears soon after the oyster finds a place to settle on the bottom of the sea. The foot is used as a feeler to test rocks, empty shells and other hard objects.
Large, crowded beds or groups of oysters can be found in rocky inlets along the coasts. Once anchored, the oyster will stay in that spot for the rest of his life. Oysters usually live about six years, but they can live as long as 20 years.
After one month of life, an oyster is about the size of a pea. He will then grow about one inch in diameter each year for three or four years. The rate of growth then slows down for the rest of his life. Some oysters can grow to be 12 inches long.
Newly hatched oysters can be swallowed by the thousands in one gulp by a fish. Crabs and other sea animals also feast on young oysters. A starfish can be an adult oyster's enemy. The starfish can pull open an oyster's shells with his tube feet.
Oyster farming is big business today. A farmer will choose an area of quiet water where the sea bottom is firm. Loose, shifting sand or soft mud could smother the oysters. Each farmer marks his plot with floats and then puts old shells or hardened clay called tiles on the sea floor. He can then buy seed oysters to "plant" his farming area.
After two to four years, when the oysters are two to four inches long, harvesting of the oysters can start.