What Bivalves Eat

Filter Feeding

• Most bivalves filter water through their shells. The water enters through one opening, passes through the gills, and then leaves through another opening. The gills have tiny cilia, like microscopic hairs, to catch as much food as possible. The food itself is mostly phytoplankton but can also include tiny nutrient-rich particles left behind by the predation or decomposition of larger organisms.

Types of Bivalves

• The majority of bivalves are either epifaunal or infaunal. Epifaunal bivalves attach themselves to surfaces, such as rocks or the hulls of ships. Infaunal bivalves bury themselves in the sediment. Infaunal bivalves extend two special siphons out of the sand -- one as a sort of intake valve for water to be filtered and the other to expel water that has already passed over the gills.

Non-Filter Feeders

• A few rare species of bivalve are actually carnivorous and eat larger prey such as worms and small crustaceans. Some bivalves are also parasitic, spending most of their lives inside the gut of sea cucumbers.

Locomotion

• Bivalves that burrow beneath the sand typically have a large foot adapted for digging. Some primitive bivalves that have not evolved specialized gills for filter feeding live by dragging themselves across surfaces and consuming detritus along the way. A few species, such as scallops, are able to swim by rapidly opening and closing their shell.