filterfeeders

Filter feeders are organisms that obtain food by straining suspended particles from water. They commonly consume phytoplankton, bacteria, and detritus. This feeding strategy occurs across many biological groups and habitats, including marine and freshwater environments.

Feeding mechanisms vary among groups. Some organisms generate water flow with cilia, flagella, or muscular pumps, while others rely on passive water movement through siphons or gills. Captured particles are trapped by specialized structures such as sponge choanocytes, ciliated gill filaments, baleen plates, or mucous nets, and are then ingested or transported to the gut.

Major examples include sponges (Porifera), which filter water through a network of chambers lined with choanocytes; bivalves (clams, oysters, mussels, scallops), which draw water across gills and trap particles; baleen whales, which use keratinized baleen plates to sieve small prey from seawater; krill and other crustaceans, which filter plankton with appendages; tunicates and some sea cucumbers, which extract particles from currents; and polychaete worms that use radioles or tentacles to catch suspended material.

Ecological role involves transferring energy from the water column to higher trophic levels, contributing to nutrient cycling, and often aiding in water clarity and quality by removing particulates. They are typically sensitive to changes in sedimentation, pollution, and temperature, and disruptions can affect feeding efficiency and reproduction.

Adaptations and diversity reflect independent evolutionary solutions to filter feeding. Sponges rely on an aquiferous system; baleen whales on plates; crustaceans on setae-bearing appendages; and bivalves on gills and labial structures, illustrating a wide range of morphological strategies for exploiting suspended organic matter.