Examples of Filter Feeders

Filter feeders are aquatic creatures that eat by straining food and other matter from the water. These ecosystem engineers -- organisms that significantly modify their habitat -- are all beneficial for cleaning the water. Common filter feeders include a variety of fish, crustaceans, sponges and bivalves.

  1. Fish

    • Filter fish range in size from small to large. Forage fish, the small fish that are common prey to birds and larger fish, work in large schools, swimming in synchronized grids with their mouths open, filtering plankton. These fish are a concentrated fuel resource for marine predators, transferring the energy from the plankton to the larger fish and marine birds. Common filter fish include anchovies, sardines, halfbeaks and capelin. Some larger fish are also considered filter feeders, such as the whale shark, megamouth shark and manta rays. The whale shark sucks in mouthfuls of water and expels it through its gills, trapping the plankton inside, whereas the megamouth shark has light-emitting organs around its mouth that lure in plankton and small fish.

    Crustaceans

    • Krill, Mysidacea, porcelain crabs and all barnacle species are considered filter feeders. Krill have front legs that serve as ideal filtering apparatuses: While the krill push themselves through the water, their front legs comb algae into the mouth. Mysidacea are small crustaceans that live near the shore. Hovering above the sea floor, they collect particles with their filter basket. Porcelain crabs have feeding appendages that are covered with setae, bristly structures that filter food from flowing water, and barnacles have modified legs that sift plankton from the water.

    Sponges

    • Because sponges lack a true circulatory system, they create their own water current for circulation. Dissolved gases are delivered to and enter the cells, and waste is pushed back out through a diffusion process. In this way, sponges pump large amounts of water. The water is pumped at a very slow rate, which allows the sponge's collar cells to capture food particles.

    Bivalves

    • Bivalves are mollusks that have a two-part shell comprising a hinged valve. Most of the thousands of species of bivalves, including scallops, clams, oysters and mussels, are filter feeders, extracting organic matter from the water. When they're buried, bivalves extend a siphon to the surface and suck in water. Otherwise, they draw water over their gills so that it runs through beating cilia. Any suspended food, such as plankton and algae, gets trapped in the mucus of the gills and then transported to the mouth.