Christina Owen, age 10, of Newport News, Va., for her question:
HOW DOES A PEARL GET INSIDE AN OYSTER?
A lot of readers write to Andy for the answer to this question. This is fine. But Andy can select only one pen pal at a time, and others may feel left out. This is sad. But if you can ask one good question, you can ask a dozen or so more. There is no limit. However, please give your name, age and complete home address in easy to read writing.
The oyster is called a bivalve because his soft body dwells between two tough shells. This is his home, and he never goes outside. The two shells have a muscular hinge, and the oyster can open and close them. This is how he lets in the sea water, which brings him dissolved oxygen and serves him scraps of floating food.
The oyster is a born house painter. He paints and repaints the inside walls of his shells to keep them smooth and shiny. He also sends out waste material and bits of debris, trying to keep his home clean and comfortable.
But he does not always succeed. Sometimes a tiny sea worm floats in between his partly open shell and fails to float out again. Sometimes a gritty grain of sand gets stuck between the shell and the oyster's soft, sensitive body. This is a scratchy, uncomfortable nuisance.
However, the oyster can solve the problem, though it takes quite a while. When he adds the next coat of paint to his inside walls he covers over the unwelcome guest. Actually, his paint is a gorgeous material called nacre. Its pearly white color glows with soft colors like a pale moonbeam.
The next time, the irritating visitor gets another layer of pearly nacre. As the years go by, these layers form a pearly bead. The original worm or grain of sand is buried deep inside the pearl, and only an X ray can tell it is there.
Many shellfish create pearls, but those of the special pearl oyster are the most beautiful and the most costly. These are the genuine oriental pearls that take many years to make. However, an oyster can produce a cultured pearl in a much shorter time.
To get a cultured pearl, a diver pokes a small bead between the oyster's shells. The oyster covers it with layers of nacre, just as if the bead were a tiny grain of sand. With a few layers of nacre, the bead has a pearly skin and becomes a cultured pearl. It is beautiful, but not as beautiful as a genuine oriental pearl.