Billy Warren, age 11, of Newport News, Virginia, for his question:
How are seashells made?
An empty seashell is an empty house. It was built by a smallish ocean dwelling animal and he lived inside it all his life. He created it from handy materials. Often it is a work of art and sometimes it is durable enough to last a million years after the owner departs.
The most handsome seashells are made by the univalve mollusks. The two shells of the clam and other bivalve mollusks usually have drab exteriors. However, the oyster and many other bivalves have interior walls lined with satin smooth mother of-pearl. But when it comes to seashell collecting, the real beauties are the univalves that create one piece shells. A mollusk builds his shell around his soft, blobby body and very often he keeps growing and adding to it all his life.
The soft bodied sea dweller would never survive a season in the hungry ocean without special protection. However, nature gives him the means to create a tough house of armor plating around himself. His body has an outer layer of special tissues called the mantle. The cells of the mantle extract atoms and molecules of certain chemicals from food and seawater. It also has an assortment of special glands that process these chemicals into suitable building materials.
The bulk of the building usually is done with calcium carbonate, a limy chemical compound of the elements calcium, carbon and oxygen. Gland cells in the mantle process this chemical into a slippery mucus, somewhat like the sniffly stuff that comes with a cold in the nose. Other glands may produce a hardening agent. These substances ooze from the mantle and dry to add layer after layer to the walls and opening of the shell.
About 100,000 mollusks create shells and each species repeats a pattern inherited from its ancestors. The best looking shells are elegantly coiled and artfully tinged with color. The coloring is added by special pigment making, cells in the mantle. The sunrise telling, who is a bivalve, has pink pigment cells strewn through his mantle. His two shells glow all over with pearly pink. Other shells build stripes from separate clusters of pigment cells. The mantle of the little cowrie has many small clusters of brown pigment cells. For reasons unknown, color operations stop from time to time. The background color of the shell is spotted with dainty little brown dots. The textile cone mollusk creates a mosaic pattern of blue tiles on a tweedy background of rusty ones.
The best looking seashells are created by mollusks that prefer to live in warm or tropical oceans. Certain hobby shops keep shells from all over the world for their conchology customers. Conchology is coined from an old word for shell. It is merely a fancy name for shell study. However, one does not have to collect fancy shells from around the world. You can find a few at low tide on your favorite beach. And all your shells do not have to come from the sea. Many fresh water mol¬lusks create handsome shells. So do many of the land dwelling mollusks known as snails.