How Does a Clam Make Its Shell?
If you have ever examined a clam shell, you may have wondered how the shell got bigger as the clam grew. A clam is born with a shell just the right size for its body. Inside the protecting shell of the living animal is a fleshy layer of tissue called the “mantle.”
The mantle oozes a limy shell liquid, which quickly hardens and becomes part of the shell. As long as a clam grows its shell also grows. The food that a clam eats provides the minerals that form the shell. The hard shell serves as a clam’s skeleton, and the soft animal inside can never leave it.
Clams create their shells from the calcium that is present in the water around them. It is the mantle that holds clams in their shell that actually produces the shell. The clam extracts the several types of calcium deposits available in the water and stores it for weeks or even months.
Then it releases the material in a kind of loose glue, adding bits to the rim of the shell as the clam grows. This material must harden into the same consistency as the rest of the shell. The ridges on the shell tell how old the clam is.