Clam Habitats
Most clams live in shallow water and bury themselves just below the surface of the sandy or muddy bottoms they prefer. However, some like deeper water, and one species, the Abra profundorum, has been found as deep as 16,000 feet below the surface of the Pacific Ocean. As creatures that rarely move in their environment, being buried protects them from the action of waves above, though there are some clams that will travel in the sea.
Types of Clams
Clams vary in many ways, including size, with some, such as the Condylocardia, being as small as a fraction of an inch while giant clams, including Tridacna gigascan found in the Indian and Pacific Oceans, grow to more than 3 feet across. Most clams are able to open and close their shells thanks to the two adductor muscles that are found at either end of the carapace, and they are equipped with a muscular burrowing foot.
Anatomy of Clams
Clams "breathe" by taking in and forcing out water. They feed by using two tubes known as the siphons, or neck. The water is forced to move in and out by the pulsing of millions of tiny hairlike filaments on the gills. Other filaments filter food from the incoming water and feed it to the mouth. Females deposit eggs into the water, where they are fertilized by sperm from the males.
Source of Food
Numerous types of clams are edible and are a popular shellfish in many parts of the world. Among the most popular types in the United States are the northern and southern quahog (Mercenaria mercenaria and Mercenaria campechiensis), which are also known as the cherrystone clam, littleneck clam and hard-shell clam, and which are found widely on the Atlantic coast. However, the type often found in chowders and soups is the soft-shell clam Mya arenaria.