AskDefine | Define copepod

Dictionary Definition

copepod n : minute marine or fresh-water crustaceans usually having six pairs of limbs on the thorax; some abundant in plankton and others parasitic on fish [syn: copepod crustacean]

User Contributed Dictionary

English

Noun

  1. Any of very many small crustaceans, of the subclass Copepoda, that are widely distributed and ecologically important; they include the water fleas

Extensive Definition

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. 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)).

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 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 to 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 . 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):
copepod in Arabic: مجدافية الأرجل
copepod in Catalan: Copèpode
copepod in German: Ruderfußkrebse
copepod in Estonian: Aerjalalised
copepod in Modern Greek (1453-): Κωπήποδα
copepod in Spanish: Copepoda
copepod in Persian: پاروپایان
copepod in French: Copepoda
copepod in Galician: Copépoda
copepod in Indonesian: Copepoda
copepod in Italian: Copepoda
copepod in Hebrew: שטרגליים
copepod in Latin: Copepoda
copepod in Latvian: Airkājvēži
copepod in Lithuanian: Irklakojai vėžiagyviai
copepod in Dutch: Eenoogkreeftjes
copepod in Japanese: カイアシ類
copepod in Norwegian: Hoppekreps
copepod in Norwegian Nynorsk: Hoppekreps
copepod in Polish: Widłonogi
copepod in Portuguese: Copépode
copepod in Finnish: Hankajalkaiset
copepod in Swedish: Hoppkräftor
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