Methods of Filter Feeding
More elaborate methods of filter feeding are seen in tube dwelling polychaetes which use tentacles to entangle the food particles. Figure shows some of the filter feeders and their feeding mechanisms. Filter feeders include both sessile and free 'living forms. The sessile forms generally accept what they get though some can selectively choose their food according to size.
Figure: Some filter feeders and their feeding mechanisms
For instance in Sabella a tube living polychaete, while large sand particles are-rejected small food particles enter the food groove. Free swimming forms are selective feeders. Examples are, many of the microcrustaceans, fishes such as herring, menhaden and basking sharks, certain birds such as flamingo, pelican and the largest of all animals the baleen whale. Among the fishes, herring have gill rakers that function as a sieve to catch plankton. The basking sharks feed exclusively on plankton and can filter up to 200 tons of water in 1 hour. The flamingo also a plankton eater uses its beak to strain small organisms from the water. However, the baleen whale is specialised for filter feeding. Its filtering apparatus consists of a series of horny plates attached to the upper jaw. As the whale swims, water flows between the plates retaining the plankton.