Filter feeders are a sub-group of suspension feeding animals that feed
by straining suspended matter and food particles from water, typically
by passing the water over a specialized filtering structure. Some
animals that use this method of feeding are clams, krill, sponges,
baleen whales, and many fish (including some sharks). Some birds, such
as flamingos and certain species of duck, are also filter feeders.
Filter feeders can play an important role in clarifying water, and are
therefore considered ecosystem engineers.
9 Marine reptiles
10 See also
13 External links
See also: Forage fish
Most forage fish are filter feeders. For example, the Atlantic
menhaden, a type of herring, lives on plankton caught in midwater.
Adult menhaden can filter up to four gallons of water a minute and
play an important role in clarifying ocean water. They are also a
natural check to the deadly red tide.
In addition to these bony fish, four types of cartilaginous fishes are
also filter feeders. 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. The megamouth shark has
luminous organs called photophores around its mouth. It is believed
they may exist to lure plankton or small fish into its mouth.[citation
needed] The basking shark is a passive filter feeder, filtering
zooplankton, small fish, and invertebrates from up to 2,000 tons of
water per hour. Unlike the megamouth and whale sharks, 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. Manta rays can
time their arrival at the spawning of large shoals of fish and feed on
the free-floating eggs and sperm. This stratagem is also employed by
whale sharks.
Filter basket of a mysid
Mysidacea are small crustaceans that live close to shore and hover
above the sea floor, constantly collecting particles with their filter
basket. They are an important food source for herring, cod, flounder,
and striped bass. Mysids have a high resistance to toxins in polluted
areas, and may contribute to high toxin levels in their
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: the six thoracopods form a very effective
"feeding basket" used to collect phytoplankton from the open water. In
the animation at the top of this page, the krill is hovering at a 55°
angle on the spot. In lower food concentrations, the feeding basket is
pushed through the 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.
Porcelain crab species have
feeding appendages covered with setae to filter food particles from
the flowing water. Most species of barnacles are
filter feeders, using their highly modified legs to sift plankton from
the water.
Baleen of a right whale
The baleen whales (Mysticeti), one of two suborders of the Cetacea
(whales, dolphins, and porpoises), are characterized by having baleen
plates for filtering food from water, rather than teeth. This
distinguishes them from the other suborder of cetaceans, the toothed
whales (Odontoceti). The suborder contains four families and fourteen
Baleen whales typically seek out a concentration of
zooplakton, swim through it, either open-mouthed or gulping, and
filter the prey from the water using their baleens. A baleen is a row
of a large number of keratin plates attached to the upper jaw with a
composition similar to those in human hair or fingernails. These
plates are triangular in section with the largest, inward-facing side
bearing fine hairs forming a filtering mat. Right whales are slow
swimmers with large heads and mouths. Their baleen plates are narrow
and very long — up to 4 m (13 ft) in
bowheads — and accommodated inside the enlarged lower lip which
fits onto the bowed upper jaw. As the right whale swims, a front gap
between the two rows of baleen plates lets the water in together with
the prey, while the baleens filter out the water. Rorquals such as
the blue whale, in contrast, have smaller heads, are fast swimmers
with short and broad baleen plates. To catch prey, they widely open
their lower jaw — almost 90° — swim through a swarm
gulping, while lowering their tongue so that the head's ventral
grooves expand and vastly increase the amount of water taken in.
Baleen whales typically eat krill in polar or subpolar waters during
summers, but can also take schooling fish, especially in the Northern
Hemisphere. All baleen whales except the gray whale feed near the
water surface, rarely diving deeper than 100 m (330 ft) or
for extended periods. Gray whales live in shallow waters feeding
primarily on bottom-living organisms such as amphipods.
Movie clip of siphon feeding
Bivalves are aquatic molluscs which have two-part shells. Typically
both shells (or valves) are symmetrical along the hinge line. The
class has 30,000 species, including scallops, clams, oysters and
mussels. Most bivalves are filter feeders (although some have taken up
scavenging and predation), extracting organic matter from the sea in
which they live. Nephridia, the shell fish version of kidneys, remove
the waste material. Buried bivalves feed by extending a siphon to the
surface. For example, oysters draw water in over their gills through
the beating of cilia. Suspended food (phytoplankton, zooplankton,
algae and other water-borne nutrients and particles) are trapped in
the mucus of a gill, and from there are transported to the mouth,
where they are eaten, digested and expelled as feces or pseudofeces.
Each oyster filters up to five litres of water per hour. Scientists
believe that the Chesapeake Bay's once-flourishing oyster population
historically filtered the estuary's entire water volume of excess
nutrients every three or four days. Today that process would take
almost a year, and sediment, nutrients, and algae can cause
problems in local waters. Oysters filter these pollutants, and
either eat them or shape them into small packets that are deposited on
the bottom where they are harmless.
Bivalve shellfish recycle nutrients that enter waterways from human
and agricultural sources. Nutrient bioextraction is “an
environmental management strategy by which nutrients are removed from
an aquatic ecosystem through the harvest of enhanced biological
production, including the aquaculture of suspension-feeding shellfish
or algae.” Nutrient removal by shellfish, which are then
harvested from the system, has the potential to help address
environmental issues including excess inputs of nutrients
(eutrophication), low dissolved oxygen, reduced light availability and
impacts on eelgrass, harmful algal blooms, and increases in incidence
of paralytic shellfish poisoning (PSP). For example, the average
harvested mussel contains: 0.8–1.2 % nitrogen and
0.06–0.08 % phosphorus Removal of enhanced biomass can not
only combat eutrophication and also support the local economy by
providing product for animal feed or compost. In Sweden, environmental
agencies utilize mussel farming as a management tool in improving
water quality conditions, where mussel bioextraction efforts have been
evaluated and shown to be a highly effective source of fertilizer and
animal feed In the U.S., researchers are investigating potential
to model the use of shellfish and seaweed for nutrient mitigation in
certain areas of Long Island Sound.
Bivalve are also largely used as bioindicators to monitor the health
of an aquatic environment, either fresh- or seawater. Their population
status or structure, physiology, behaviour or their content of certain
elements or compounds can reveal the contamination status of any
aquatic ecosystem. They are extremelly useful as they are sessile -
which means they are closely representative of the environment where
they are sampled or placed (caging) -, and they are breathing water
all along the day, exposing their gills and internal tissues:
bioaccumulation. One of the most famous project in that field is the
Mussel Watch Programme in U.S. but today they are used worldwide for
that purpose (ecotoxicology).
Tube sponges attracting small reef fish
The arcuate bill of this lesser flamingo is well adapted to bottom
The pink coloring of
Pterodaustro is hypothetical, but is based on
ecological similarities to flamingoes
Sponges have no true circulatory system; instead, they create a water
current which is used for circulation. Dissolved gases are brought to
cells and enter the cells via simple diffusion. Metabolic wastes are
also transferred to the water through diffusion. Sponges pump
remarkable amounts of water. Leuconia, for example, is a small
leuconoid sponge about 10 cm tall and 1 cm in diameter. It
is estimated that water enters through more than 80,000 incurrent
canals at a speed of 6 cm per minute. However, because Leuconia
has more than 2 million flagellated chambers whose combined diameter
is much greater than that of the canals, water flow through chambers
slows to 3.6 cm per hour. Such a flow rate allows easy food
capture by the collar cells. Water is expelled through a single
osculum at a velocity of about 8.5 cm/second: a jet force capable
of carrying waste products some distance away from the sponge.
The moon jellyfish has a grid of fibres which are slowly pulled
through the water. The motion is so slow that copepods cannot sense it
and do not react with an escape response.
An undulating live Aurelia in the
Baltic Sea showing the grid in
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).
Other filter-feeding cnidarians include sea pens, sea fans, plumose
anemones, and Xenia.
Flamingos filter-feed on brine shrimp. Their oddly shaped beaks are
specially adapted to separate mud and silt from the food they eat, and
are uniquely used upside-down. The filtering of food items is assisted
by hairy structures called lamellae which line the mandibles, and the
large rough-surfaced tongue.
Ctenochasmatoidea as a group has been listed as
filter-feeders, due to their long, multiple slender teeth, clearly
well adapted to trap prey. However, only
Pterodaustro showcases a
proper pumping mechanism, having up-turned jaws and powerful jaw and
tongue musculature. Other ctenochasmatoids lack these, and are now
instead thought to have been spoonbill-like catchers, using their
specialised teeth simply to offer a larger surface area. Tellingly,
these teeth, while small and numerous, are comparatively unspecialised
to the baleen-like teeth of Pterodaustro.
Boreopterids are thought to have relied on a kind of rudimentary
filter feeding, using their long, slender teeth to trap small fish,
though probably lacking the pumping mechanism of Pterodaustro. In
essence, their foraging mechanism was similar to that of modern young
Filter feeding habits are conspicuously rare among
reptiles, the main filter feeding niche being seemingly instead
occupied by pachycormid fish. However, some sauropsids have been
suggested to have engaged in filter feeding.
Henodus was a placodont
with unique baleen-like denticles and features of the hyoid and jaw
musculature comparable to those of flamingos. Combined with its
lacustrine environment, it might have occupied a similar ecological
niche. In particular, it was probably a herbivore, filtering
out algae and other small-sized flora from the substrates.
Stomatosuchidae is a family of freshwater crocodylomorphs with
rorqual-like jaws and minuscule teeth, and the unrelated Cenozoic
Mourasuchus shares similar adaptations.
Hupehsuchia is a lineage of
Triassic reptiles adapted for suspension feeding. Some
plesiosaurs might have had filter-feeding habits.
Spider web - the only terrestrial equivalent of a filter feeder
^ H. Bruce Franklin (March 2006). "Net Losses: Declaring War on the
Menhaden". Mother Jones. Retrieved 27 February 2009. Extensive
article on the role of menhaden in the ecosystem and possible results
^ Ed. Ranier Froese and Daniel Pauly. "Rhincodon typus". FishBase.
Retrieved 17 September 2006.
^ Martin, R. Aidan. "Elasmo Research". ReefQuest. Retrieved 17
^ "Whale shark".
Ichthyology at the Florida Museum of Natural History.
Retrieved 17 September 2006.
^ a b C. Knickle; L. Billingsley & K. DiVittorio. "Biological
Profiles basking shark". Florida Museum of Natural History. Retrieved
^ 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
^ a b c d Bannister, John L. (2008). "
Baleen Whales (Mysticetes)". In
Perrin, William F.; Würsig, Bernd; Thewissen, J. G. M. Encyclopedia
of Marine Mammals. Academic Press. pp. 80–89.
Oyster Reefs: Ecological importance". US National Oceanic and
Atmospheric Administration. Archived from the original on 3 October
2008. Retrieved 2008-01-16.
^ The comparative roles of suspension-feeders in ecosystems. Springer.
Dordrecht, 359 p.
^ NOAA. "Nutrient Bioextraction Overview". Long Island Sound Study.
^ Stadmark and Conley. 2011.
Mussel farming as a nutrient reduction
measure in the Baltic Sea: consideration of nutrient biogeochemical
cycles. Marine Pollution Bull. 62(7):1385-8
^ Lindahl, O, Hernroth, R., Kollberg, S., Loo, L.-O, Olrog, L.,
Rehnstam-Holm, A.-S., Svensson, J., Svensson S., Syversen, U. (2005).
"Improving marine water quality by mussel farming: A profitable
solution for Swedish society". Ambio 34 (2): 131–138.
^ Miller and Wands. "Applying the System Wide
(SWEM) for a Preliminary Quantitative Evaluation of Biomass Harvesting
as a Nutrient Control Strategy for Long Island Sound" (PDF).
^ See Hickman and Roberts (2001) Integrated principles of zoology —
11th ed., p.247
^ a b Wilton, Mark P. (2013). Pterosaurs: Natural History, Evolution,
Anatomy. Princeton University Press. ISBN 0691150613.
^ Pilleri, G., G. Marcuzzi and O. Pilleri (1982). "Speciation in the
Platanistoidea, systematic, zoogeographical and ecological
observations on recent species". Investigations on
^ Rieppel, O. (2002). Feeding mechanisms in
sauropterygians: the anatomy of a successful invasion of
Zoological Journal of the Linnean Society, 135, 33-63
^ Naish, D. 2004. Fossils explained 48. Placodonts. Geology Today 20
^ Chun, Li; Rieppel, Olivier; Long, Cheng; Fraser, Nicholas C. (May
2016). "The earliest herbivorous marine reptile and its remarkable jaw
apparatus". Science Advances. 2 (5): e1501659.
^ Sanderson, S. L.; Wassersug, R. (1990). "Suspension-feeding
vertebrates". Scientific American 262 (3): 96–101.
^ "Plesiosaur Machinations XI: Imitation Crab Meat Conveyor Belt and
the Filter Feeding Plesiosaur". Archived from the original on 26
Bullivant JS (1968). "A Revised Classification of Suspension Feeders".
Tuatara. 16 (2): 151–160.
Some aspects of water filtering activity of filter-feeders //
Hydrobiologia. 2005. Vol. 542, No. 1. P. 275 – 286
Filter feeder of krill
Mussel Watch Programme
Diseases and parasites
Fish as food
Fear of fish
Hypoxia in fish
Sensory systems in fish
Ampullae of Lorenzini
Jamming avoidance response
Capacity for pain
Surface wave detection
Life history theory
Polyandry in fish
Fin and flipper locomotion
Tradeoffs for locomotion in air and water
Diel vertical migration
Sleep in fish
Fish common names
Fish on stamps
Glossary of ichthyology