The Specter Clam
Most bivalve mollusks (clams, mussels, oysters, etc.) are filter-feeders, straining large amounts of water to get their food, usually microscopic plants (phytoplankton). Exceptions to this are marine bivalves that prey on small critters such as crustaceans. These clams, known as septibranch bivalves, use a flexible, muscular "wall", or septum, which acts as a pump, creating a sudden negative pressure that sucks in nearby prey. The Specter Clam, Dilemma spectralis Leal, 2008,