Siphon (mollusc)

A siphon is an anatomical structure which is part of the body of aquatic molluscs in three classes: Gastropoda, Bivalvia and Cephalopoda. In other words, a siphon is found in some saltwater and freshwater snails, in some clams, and in octopus, squid and relatives.

Siphons in molluscs are tube-like structures in which water flows (or more rarely in which air flows). The water flow is used for one or more purposes such as locomotion, feeding, respiration, and reproduction. The siphon is part of the mantle of the mollusc, and the water flow is directed to (or from) the mantle cavity.

A single siphon occurs in some gastropods. In those bivalves which have siphons, the siphons are paired. In cephalopods, there is a single siphon or funnel which is known as a hyponome.

In gastropods

In some (but not all) sea snails, marine gastropod molluscs, the animal has an anterior extension of the mantle called a siphon, or inhalant siphon, through which water is drawn into the mantle cavity and over the gill for respiration.