Copepod
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Calanoida |
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat and they constitute the biggest source of protein in the oceans.[1] Many species are planktonic, but more are benthic, and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests, bogs, springs, ephemeral ponds and puddles, damp moss, or water-filled recesses (phytotelmata) of plants such as bromeliads and pitcher plants. Many live underground in marine and freshwater caves, sinkholes, or stream beds. Copepods are sometimes used as bioindicators (see particle (ecology)).
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Ecology
Planktonic copepods are important to global ecology and the carbon cycle; They are usually the dominant members of the zooplankton, and are major food organisms for small fish, whales, seabirds and other crustaceans such as krill in the ocean and in fresh water. Some scientists say they form the largest animal biomass on earth. They compete for this title with Antarctic krill (Euphausia superba). Because of their smaller size and relatively faster growth rates, however, and because they are more evenly distributed throughout more of the world's oceans, copepods almost certainly contribute far more to the secondary productivity of the world's oceans, and to the global ocean carbon sink than krill, and perhaps than all other groups of organisms together. The surface layers of the oceans are currently believed to be the world's largest carbon sink, absorbing about 2 billion tonnes of carbon a year, the equivalent to perhaps a third of human carbon emissions, thus reducing their impact. Many planktonic copepods feed near the surface at night, then sink into deeper water during the day to avoid visual predators. Their moulted exoskeletons, faecal pellets and respiration at depth all bring carbon to the deep sea.
Some copepods are parasitic[1][1] and have strongly modified bodies. They attach themselves to fish, sharks, marine mammals, and many kinds of invertebrates such as molluscs, tunicates, or corals. They live as endo- or ectoparasites on fish or invertebrates in fresh water as well as in marine environments.
Characteristics
Copepods are typically 1 millimetre (0.0393700787 in) to 2 millimetres (0.0787401574 in) long, with a teardrop shaped body and large antennae. Although like other crustaceans they have an armoured exoskeleton, they are so small that in most species this armour, and the entire body, is almost totally transparent. Copepods have a single eye, usually bright red and in the centre of the transparent head. Some polar copepods reach 1 (0.393700787 ). Most of the smaller copepods feed directly on phytoplankton, catching cells singly, but a few of the larger species are predators of their smaller relatives. Herbivorous copepods, particularly those in rich cold seas, store up energy from their food as oil droplets while they feed in the spring and summer plankton blooms. These droplets may take up over half of the volume of the body in polar species.
Many species have neurons surrounded by myelin, which is very rare among invertebrates (other examples are some annelids and malacostracan crustaceans like palaemonid shrimp and penaeids). Even rarer is the fact that the myelin is highly organized, resembling the well-organized wrapping found in vertebrates (Gnathostomata).
Some copepods are very evasive and can jump with extreme speed over a few millimeters (warning: takes some time to load to the correct speed):
Classification
Copepods form a subclass belonging to the subphylum Crustacea (crustaceans). Some authors consider the copepods to be a full class. The group contains ten orders with some 14,000 described species. A scientist that studies copepods is a copepodologist.
Water supply
Copepods are sometimes found in the public mains water supply, especially systems where the water is not filtered, such as New York City and Boston, Massachusetts. This is not usually a problem in treated water supplies. In some tropical countries, such as Peru and Bangladesh, a correlation has been found between copepods and cholera in untreated water, because the cholera bacteria attach to the surfaces of planktonic animals. The risk of cholera from infected water can be reduced by filtering out the copepods (and other matter), for example with a cloth filter.
References
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The references in this article would be clearer with a different or consistent style of citation, footnoting, or external linking. |
External links
- Diversity and geographical distribution of pelagic copepoda
- Rudi Strickler copepod videos
- The virtual copepod page
- Copepod World
- Copepods and cholera in untreated water
- Copepod links, www.copepod.de
- CNN report: New York Times: The Water's Fine, but Is It Kosher?
- Copepodologist's Cabinet: A Biographical & Bibliographical History
See also
ca:Copèpode de:Ruderfußkrebse et:Aerjalalised el:Κωπήποδαfa:پاروپایان fr:Copepoda gl:Copépoda id:Copepoda it:Copepoda he:שטרגליים la:Copepoda lv:Airkājvēži lt:Irklakojai vėžiagyviai nl:Eenoogkreeftjes ja:カイアシ類 no:Hoppekreps nn:Hoppekrepsfi:Hankajalkaiset sv:Hoppkräftor
