How do bivalves filter food particles from water?

Most modern bivalves are suspension feeders that filter food particles—such as plant detritus, bacteria, and algae—from the water column using specialized gills called ctenidia.

The process functions as follows:

• Water Circulation: Complex arrays of cilia located on the gill filaments create a continuous water current that draws water into the mantle cavity through an incurrent siphon.12
• Filtration: As water passes through the gill lamellae, the gills act as a sieve, trapping suspended food particles against the gill surface.32
• Transport: The trapped particles are bound in mucus and transported by ciliary action along specific tracts—either the gill axes or the ventral margins—toward the labial palps.12
• Selection and Ingestion: The labial palps further sort the collected material. Suitable food is directed to the mouth for ingestion, while rejected particles, known as pseudofeces, are expelled from the mantle cavity.2

While this is the standard mechanism for most bivalves, some species have evolved different strategies, such as the predatory feeding habits of certain deepwater bivalves or the symbiotic relationship with algae found in giant clams.12