filterfeeding

Filter feeding, or suspension feeding, is a feeding strategy in which animals obtain food by straining suspended particles from water. Organisms that use this method are often mobile and rely on specialized structures or behaviors to separate edible matter from the water column, including plankton, detritus, and organic particles.

Diverse groups employ filter feeding in different ways. Baleen whales, for example, swim with mouths wide open and push water through baleen plates that trap small prey like krill. In bivalves such as oysters, clams, and mussels, water is drawn in through siphons and passes over gills that capture particles; mucus and cilia then move the food toward the mouth. Sponges filter water through a network of canals using choanocytes to capture particles, generating water flow that delivers food to cells. Some ray-finned fishes, such as paddlefish, sturgeon, and basking sharks or manta rays, use gill rakers or similar structures to sieve zooplankton from their inhaled water. Birds including flamingos filter feed by drawing water through specially fashioned beaks that trap small organisms with lamellae inside the mouth.

Other animals, such as feather duster worms and other polychaetes, use radioles or branched feeding structures to capture suspended particles. Filter feeding is often energetically efficient in nutrient-poor environments and can support large, slow-moving or sessile organisms.

Ecologically, filter feeders play a key role in linking primary production to higher trophic levels and in cycling nutrients, while they can be sensitive to changes in plankton abundance, water quality, and sedimentation.