Siphon (mollusc)

[1] This siphon is a soft fleshy tube-like structure equipped with chemoreceptors which "smell" or "taste" the water, in order to hunt for food.

Freshwater apple snails in the genera Pomacea and Pila have an extensible siphon made from a flap of the left mantle cavity.

They use this siphon in order to breathe air while they are submerged in water which has a low oxygen content so they cannot effectively use their gill.

It reduces their vulnerability to being attacked and eaten by birds because it enables the apple snails to breathe without having to come all the way up to the surface, where they are easily visible to predators.

The function of these siphons is to reach up to the surface of the sediment, so that the animal is able to respire, feed, and excrete, and also to reproduce.

Bivalves which have extremely long siphons, like the geoducks pictured here, live very deeply buried, and are hard to dig up when clamming.

Depending on the species and family concerned, some bivalves utilize their inhalant siphon like the hose of a vacuum cleaner, and actively suck up food particles from the marine substrate.

Most other bivalves ingest microscopic phytoplankton as food from the general water supply, which enters via the inhalant siphon and reaches the mouth after passing over the gill.

The hyponome or siphon is the organ used by cephalopods to expel water, a function that produces a locomotive force.