How Do Clams Eat?
Most clams burrow in sandy or muddy bottoms in shallow water. The clam gets its food from the water in an unusual way. At one end of its body is a pair of hollow tubes called siphons which can be extended outside the shell. To eat, the clam sucks in water through one of its siphons, bringing food and oxygen into its body. A second siphon squirts the water out.
Clams known as “soft-shell” clams have siphons that may be a foot long. Because the extra-long siphon was once mistaken for its neck, this clam is sometimes called a “long-neck” clam.
Clams are filter-feeders. Ocean clams feed at high tide, when the sand in which they are buried is covered by water. At low tide, clams wait for the water to return. Freshwater clams feed all the time. Clams extend their siphons or “necks” to take in water for oxygen and food. They exhale the water through the siphon after respiration and removal of nutritious particulates (ingestion).
Food to a clam is the suspended particles present in the water of its habitat. Much of this mass is made up of plankton, ubiquitous at the very top level of ocean water and otherwise circulated through all but the deepest (intercontinental) sea levels. For clams to eat, the water available to them must be in motion.
Clams respiration works through the movement of water across their gills, although some oxygen intake takes place along the body mantle. Water is propelled across the gills and the body proper by means of cilia, tiny hair like protrusions of protein. Oxygen intake is low, and estimated at under ten percent of that present in the amount of total water processed.