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, a deep-sea dweller from off Vanuatu in the SW Pacific (first described and named by yours truly) is one of those predatory bivalves, . Preserved Specter Clams had whole crustaceans in their stomachs. There is a chance, given that Dilemma clams live permanently attached to rocks, that Specter Clams may use some form of chemical attraction to lure nearby prey.
Dilemma spectralis Leal, 2008. Left, entire preserved clam about one-inch long; center, shell removed; right, drawing (by Kimberly Nealon) of animal showing dissected stomach with prey (isopod crustacean) and incurrent siphon (opening through which prey is ingested.)