How do burrowing bivalves use siphons to feed while buried?

Burrowing bivalves utilize long, tentacle-fringed siphons to maintain a connection with the water column while remaining safely buried within sediments like sand or mud.12

These siphons are formed from the folds of the mantle tissue and consist of two distinct channels: an inhalant siphon and an exhalant siphon. The process functions as follows:12

• Water Intake: The action of cilia on the bivalve's gills (ctenidia) draws a continuous current of water into the mantle cavity through the inhalant siphon.32
• Feeding and Respiration: As water passes through the gills, the filaments—which are often elongated and folded to increase surface area—sieve food particles (such as algae, bacteria, and plant detritus) from the water. These particles are trapped in mucus and transported to the labial palps for processing and ingestion. Simultaneously, the gills facilitate oxygen exchange.32
• Waste Removal: After the water has been filtered and used for respiration, it is expelled from the mantle cavity through the exhalant siphon, carrying away waste products.2

This specialized body organization allows these animals to live in a vertical, head-down orientation, effectively escaping the sediment surface while continuing to feed and breathe.2