Filter feeder
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Filter feeders (also known as suspension feeders) are animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized structure, such as the baleen of baleen whales. Some animals that use this method of feeding are clams, krill, flamingos, sponges, some sharks and the baleen whales.
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[edit] Filter feeding in krill
The Antarctic krill manages to directly utilize the minute phytoplankton cells, which no other higher animal of krill size can do. This is accomplished through filter feeding, using the krill's developed front legs, providing for a very efficient filtering apparatus:[1] the six thoracopods form a very effective "feeding basket" used to collect phytoplankton from the open water. In the movie linked to the right, the krill is hovering at a 55° angle on the spot. In lower food concentrations, the feeding basket is pushed through the excellent water for over half a meter in an opened position, and then the algae are combed to the mouth opening with special setae on the inner side of the thoracopods.
[edit] Filter feeding in Moon Jelly
Click on the images for higher resolutions.
 high resolution in situ image of an undulating life Aurelia in the Baltic Sea showing the grid of the fibres which are slowly pulled through the water. The motion is so slow that copepods can not sense it and don't react with an escape response |
 higher magnification showing a prey item, probably a copepod |
 The prey is then drawn to the body by contracting the fibres in a corkscrew fashion (image taken with an ecoSCOPE |
[edit] Filter feeding in mysids
These 3 cm long animals live close to shore and hover above the sea floor, constantly collecting particles. They are an important food source for herring, cod, flounder, striped bass. Mysids have a high resistance to toxins in polluted areas, and may contribute to high toxin levels in their predators.
[edit] Filter feeding in sharks
There are 3 shark species that are filter feeders. The whale shark, the basking shark and the megamouth shark.
The whale shark sucks in a mouthful of water, closes its mouth and expels the water through its gills. During the slight delay between closing the mouth and opening the gill flaps, plankton is trapped against the dermal denticles which line its gill plates and pharynx. This fine sieve-like apparatus, which is a unique modification of the gill rakers, prevents the passage of anything but fluid out through the gills (anything above 2 to 3 mm in diameter is trapped). Any material caught in the filter between the gill bars is swallowed. Whale sharks have been observed "coughing" and it is presumed that this is a method of clearing a build up of food particles in the gill rakers.[2][3][4]
The basking shark is a passive filter feeder, filtering zooplankton, small fish and invertebrates from up to 2,000 tons of water per hour.[5] Unlike the megamouth shark and whale shark, the basking shark does not appear to actively seek its quarry, but it does possess large olfactory bulbs that may guide it in the right direction. Unlike the other large filter feeders, it relies only on the water that is pushed through the gills by swimming; the megamouth shark and whale shark can suck or pump water through their gills.[5]
The megamouth has luminous organs called photophores around its mouth. It is believed they may exist to lure plankton or small fish into its mouth.
[edit] See also
- Particle
- Spider web - the only terrestrial equivalent of a filter feeder
Contrast with:
[edit] References
- ^ Kils, U.: Swimming and feeding of Antarctic Krill, Euphausia superba - some outstanding energetics and dynamics - some unique morphological details. In Berichte zur Polarforschung, Alfred Wegener Institute for Polar and Marine Research, Special Issue 4 (1983): "On the biology of Krill Euphausia superba", Proceedings of the Seminar and Report of Krill Ecology Group, Editor S. B. Schnack, 130-155 and title page image.
- ^ Ed. Ranier Froese and Daniel Pauly. Rhincodon typus. FishBase. Retrieved on 17 September 2006.
- ^ Martin, R. Aidan.. Elasmo Research. ReefQuest. Retrieved on 17 September 2006.
- ^ Whale shark. Icthyology at the Florida Museum of Natural History. Retrieved on 17 September 2006.
- ^ a b C. Knickle, L. Billingsley & K. DiVittorio. Biological Profiles basking shark. Florida Museum of Natural History. Retrieved on 2006-08-24.
