Siphonfeeding

Siphonfeeding is a feeding strategy used by various aquatic organisms in which water containing suspended food particles is drawn into the body through a tubular opening called a siphon. The inflowing water is directed to a filtering or trapping surface, such as gills or mucus-coated epithelia, where particles are captured and transported to the mouth for digestion. The filtered water is expelled through a separate excurrent siphon. This arrangement allows the animal to obtain food while maintaining a largely stationary or buried position.

Mechanism and anatomy commonly involve a paired or single siphon that serves as the intake channel and an adjacent or separate outlet for water discharge. In many filter-feeding mollusks, especially bivalves, the siphons extend from the mantle and help create a steady flow of water through the mantle cavity. Food particles are captured on gills and labial structures, moved by cilia and mucus to the mouth, and the cleaned water exits via the excurrent siphon. In some species, long siphons enable an animal to remain buried or partially buried in sediment while still accessing fresh feeding water.

Ecology and evolution: Siphonfeeding supports sedentary or burrowing lifestyles by enabling continuous feeding with minimal movement. It is especially common among bivalves such as clams, mussels, oysters, and some freshwater forms, as well as other sessile filter feeders like certain ascidians. Limitations include susceptibility to sediment clogging, dependency on suitable water flow, and reduced feeding efficiency in turbid or polluted waters.

Overall, siphonfeeding is a specialized, water-driven feeding strategy that enhances access to food resources for organisms anchored in substrates or living in constrained habitats.