A clam is a bivalve mollusk, possessing a symmetrical hinged shell to protect it from predators and the elements. Many clams burrow under the bed of the ocean or freshwater environment that they live in, although some attach themselves to rocks in relatively shallow areas. In addition to being eaten by many marine animals, clams are also a delicacy for many humans as well, especially in coastal regions. Clams are readily available fresh at many fish markets, and are also canned for shipment and sale around the world.
Clams are in the class Pelecypoda, and a number of individual animals are considered to be clams. Generally, in addition to the symmetrical shell, a clam also has a roughly oval shape, reproduces sexually, and has a simple open circulatory system. While a clam does have major organs such as a heart and kidneys, it lacks eyes and a brain. Clams eat plankton, and are eaten by many ocean going mammals and large fish. Burrowing clams are relatively easy to harvest, and clam digging is a frequent activity in some coastal regions. Clams which have attached themselves to rocks need to be gently pried off.
There are two divisions for clams: hard shell clams and soft shell clams. The term “soft shell clam” is a bit of a misnomer, as the shells of the clams are merely brittle and thin, rather than soft. Often, the clam cannot retract its neck all the way, meaning that a small portion of the clam sticks outside the shell at all times. Examples of soft shell clams include geoducks, razors, and steamers. Hard shell clams have a more typically solid shell, and they are able to retract their bodies all the way into the shell. Some common hard shell clams include chowders, littlenecks, and butters.
Because shellfish such as clams can accumulate biotoxins like those contained in a red tide, clams should only be collected when the water is safe. Most coastal regions have a hotline which can be called for information about whether or not shellfish is safe. In addition, shellfish can go bad very quickly, so you should always cook clams when they are alive. In the case of hard shell clams, the shells will be tightly closed if they are alive. If a shell is open, gently tap on it. A live clam will snap shut. To test the viability of soft shell clams, touch their necks to see if they retract. All dead clams should be discarded.