How does Lingula feed while living in mud or sand?

When living in mud or sand, the lamp shell genus Lingula remains attached at the bottom of its burrow. To feed, it protrudes its anterior end above the surface of the sediment and arranges its setae (bristle-like structures) into three distinct tubes.1

These tubes function to channel water into specific currents: lateral incoming currents, which bring in food, and a medial or central outgoing current, which carries away waste. Like other brachiopods, Lingula uses a lophophore—a horseshoe-shaped organ equipped with hairlike cilia—to filter minute organisms and organic particles from the seawater. The cilia move these food particles, often trapped in mucus, toward the animal's mouth.1