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clam,common name for certain bivalvebivalve,
aquatic mollusk of the class Pelecypoda ("hatchet-foot") or Bivalvia, with a laterally compressed body and a shell consisting of two valves, or movable pieces, hinged by an elastic ligament.
..... Click the link for more information. mollusks, especially for marine species that live buried in mud or sand and have valves (the two pieces of the shell) of equal size. The oval valves, which cover the right and left sides of the animal, are hinged together at the top by an elastic ligament. Clams burrow by means of a muscular foot, located at the front end, which can be extruded between the valves. The head, located within the shell, is rudimentary, without eyes or antennae. Water containing oxygen and food particles enters through an incurrent siphon; waste-containing water is expelled through an excurrent siphon. The two tubes project from the end opposite the foot and may be united in a single structure called the neck. The sexes are usually separate. Eggs and sperm are deposited in the water; the fertilized egg develops into a free-swimming larva without a shell, which may not attain the adult form for several months.
Clams are highly valued as food. The soft-shell clam, or steamer (Mya arenaria), of both coasts of North America, is one of the most popular eating clams. The hard-shell clam (Mercenaria mercenaria), also known as the northern quahog, is abundant from the Gulf of St. Lawrence to Texas. The name quahog is from the Naragansett; some Native Americans used the violet portion of the shell for wampum. Small hard-shell clams are called littlenecks; somewhat larger ones, cherrystones. The ocean quahog (Artica islandica) is among the longest-lived animals; one was estimated to be between 405 and 410 years old in 2007. The razor clam (Ensis), shaped like an old-fashioned straight razor, burrows rapidly and swims by means of its foot. The Atlantic razor clam, found from Labrador to W Florida and prized for its flavor, may attain lengths of 10 in. (25 cm). The Eastern surf clam (Spisula solidissima) frequents sandy bottoms in shallow water from Labrador to North Carolina and is much used for bait. There are also several Pacific surf clams. Other Pacific clams include the succulent Pismo clam (Tivela stultorum), found from mid-California southward and protected by law from overdigging, and the geoduckgeoduck
, common name of a Pacific clam, Panope generosa. The largest intertidal burrowing bivalve in the world, the geoduck may weigh up to 12 lb (5.4 kg). The shell is thin, lacks teeth, and may attain a length of 8 in. (20 cm).
..... Click the link for more information. of the Pacific Northwest, which may weigh as much as 12 lb (5.4 kg). The valves of many small clams are familiar seashells, such as those of the pea-sized amethyst gem clam. The giant clamgiant clam,
common name for the largest bivalve mollusk in the world, Tridacna gigas, also known as the bear's paw clam. The giant clam may weigh over 500 lb (225 kg) and attain a length of over 4 ft (120 cm). The heavy shell is coarsely fluted and toothed.
..... Click the link for more information. of the S Pacific Ocean may reach a weight of 500 lb (227 kg) and a length of 5 ft (150 cm).
There are two families of freshwater bivalves called clams. The small freshwater clams (family Sphaeriidae) are hermaphroditic; they retain the fertilized eggs in a brood pouch and bear young with shells. The large freshwater clams (family Unionidae) are also called freshwater musselsmussel,
edible freshwater or marine bivalve mollusk. Mussels are able to move slowly by means of the muscular foot. They feed and breathe by filtering water through extensible tubes called siphons; a large mussel filters 10 gal (38 liters) of water per day.
..... Click the link for more information. ; the nacreous inner layer of their shells is a source of mother-of-pearl. The larvae of these clams are parasitic on the gills of fish.
The term clam is sometimes used synonomously with bivalve; in this sense it includes the oystersoyster,
bivalve mollusk found in beds in shallow, warm waters of all oceans. The shell is made up of two valves, the upper one flat and the lower convex, with variable outlines and a rough outer surface.
..... Click the link for more information. , scallopsscallop
marine bivalve mollusk. Like its close relative the oyster, the scallop has no siphons, the mantle being completely open, but it differs from other mollusks in that both mantle edges have a row of steely blue "eyes" (which use a mirror consisting of
..... Click the link for more information. , and marine mussels. Clams are classified in the phylum MolluscaMollusca
, taxonomic name for the one of the largest phyla of invertebrate animals (Arthropoda is the largest) comprising more than 50,000 living mollusk species and about 35,000 fossil species dating back to the Cambrian period.
..... Click the link for more information. , class Pelecypoda or Bivalvia.
See also ALAM.
["CLAM Programmer's Manual", Ray d'Inverno & Russell-Clark, King's College London, 1971].