Cyclops is one of the most common genera of freshwater copepods, comprising over 400 species. Together with other similar-sized non-copepod fresh-water crustaceans, especially cladocera, they are commonly called water fleas. The name Cyclops comes from the Cyclops of Greek mythology, as they have a single large eye; in Cyclops, the eye may be either red or black.

Anatomy Cyclops individuals may range from to 5 mm longReed & McIntyre (1995). "Cyclops strenuus (Fischer, 1851) sensu lato in Alaska and Canada, with new records of occurrence" and are clearly divided into two sections. The broadly oval front section comprises the head and the first five thoracic segments. The hind part is considerably slimmer and is made up of the sixth thoracic segment and the four legless pleonic segments. Two caudal appendages project from the rear. Although they may be difficult to observe, Cyclops has five pairs of legs. The long first antennae, two in number, are used by the males for gripping the females during mating. Afterwards, the female carries the eggs in two small sacs on her body. The larvae, or nauplii, are free-swimming and unsegmented.

Habitat Cyclops has a cosmopolitan distribution in fresh water, but is less frequent in brackish water. It lives along the plant-covered banks of stagnant and slow-flowing bodies of water, where it feeds on small fragments of plant material, animals (such as nematodes), or carrion. It swims with characteristic jerky movements. Cyclops has the capacity to survive unsuitable conditions by forming a cloak of slime. Average lifespan is about three months.

Public health importance Cyclops is intermediate host of dracunculiasis (guinea-worm disease) and fish tapeworm (Diphyllobothrium latum) infection. This disease can be passed to humans through drinking infected water. Dracunculiasis will rarely cause death but is a weakening disease.

Control methods Cyclops can be controlled using physical, chemical, biological and engineering methods.

Physical Straining of water through piece of fine cloth is sufficient to remove Cyclops. It can also be killed by boiling water, as it is easily killed by heat at 60 °C.

Chemical Chlorine in strength of 22 ppm destroys Cyclops in 2 hours; although this concentration of chlorine gives bad odour and taste to water. Excess chlorine can be removed with sodium thiosulfate.

Biological Small fish, like barbel and Gambusia, feed on Cyclops. This type of predation was used in the South Indian state of Karnataka to eradicate dracunculiasis. Additionally, Cyclops is widely sold in frozen packages at pet shops and fish stores as a supplemental fish food.

Engineering Provision of drinking water through piping water supply, use of tubewells and abolition of stepwells are effective measures on community level.

Species

Cyclops abnobensis Brehm, 1958 Cyclops abyssicola Lilljeborg, 1901 Cyclops abyssorum G. O. Sars, 1863 Cyclops acanthoides Douwe, 1914 Cyclops adolescens Herrick, 1882 Cyclops aequoreus Fischer, 1860 Cyclops affinis G. O. Sars, 1863 Cyclops africanus Bourne, 1893 Cyclops agilis Koch, 1838 Cyclops agiloides G. O. Sars, 1909 Cyclops alajensis Ulyanin, 1874 Cyclops albicans G. W. Smith, 1909 Cyclops albidus Jurine, 1820 Cyclops alius Kiefer, 1935 Cyclops alpestris Daday, 1885 Cyclops alticola Kiefer, 1935 Cyclops americanus Marsh, 1893 Cyclops amoenus Mann, 1940 Cyclops anceps (Richard, 1897) Cyclops angustus S. Grassel, 1999 Cyclops ankyrae Mann, 1940 Cyclops anninae Menzel, 1926 Cyclops annulatus Wierzejski, 1893 Cyclops annulicornis Koch, 1838 Cyclops anophthalmus Joseph, 1882 Cyclops argulus (Fabricius, 1793) Cyclops armatus Tilesius, 1815 Cyclops arnaudi G. O. Sars, 1908 Cyclops aspericornis Daday, 1906 Cyclops ater Herrick, 1882 Cyclops attenuatus G. O. Sars, 1909 Cyclops aurantius Fischer, 1860 Cyclops australis King, 1855 Cyclops baicalensis Vassilieva, 1950 Cyclops bathybius Daday, 1896 Cyclops bicolor G. O. Sars, 1863 Cyclops bicuspidatus Claus, 1857 Cyclops bisetosus Rehberg, 1880 Cyclops bissextilis Willey, 1925 Cyclops bistriatus Koch, 1838 Cyclops bodamicus Vosseler, 1886 Cyclops bodanus Kiefer, 1954 Cyclops bogoriensis Menzel, 1926 Cyclops bohater Kozminski, 1933 Cyclops bohemicus Srámek-Husek, 1938 Cyclops bopsini Studer, 1878 Cyclops brachypus (Kiefer, 1955) Cyclops bracteatus (O. F. Müller, 1776) Cyclops brasiliensis Dana, 1849 Cyclops brehmi (Kiefer, 1927) Cyclops brevicaudatus Claus, 1857 Cyclops brevicornis Baird, 1835 Cyclops brevicornis Claus, 1857 Cyclops brevipes Brady, 1910 Cyclops brevisetosus Daday, 1885 Cyclops brevispinosus Herrick, 1884 Cyclops brucei T. Scott, 1899 Cyclops buxtoni Gurney, 1921 Cyclops cabanensis Russki, 1889 Cyclops caeruleus O. F. Müller, 1776 Cyclops canadensis Einsle, 1988 Cyclops canthocarpoides Fischer, 1851 Cyclops capillatus G. O. Sars, 1863 Cyclops capilliferus S. A. Forbes, 1893 Cyclops carolinianus Yeatman, 1944 Cyclops caspicus Lindberg, 1942 Cyclops castor Desmarest, 1825 Cyclops caudatus (G. O. Sars, 1927) Cyclops cavernarum Ulrich, 1902 Cyclops ceibaensis Marsh, 1919 Cyclops cerberus Chappuis, 1934 Cyclops charon Kiefer, 1931 Cyclops chelifer O. F. Müller, 1776 Cyclops chiltoni G. M. Thomson, 1883 Cyclops christianensis Boeck, 1872 Cyclops ciliatus G. O. Sars, 1909 Cyclops clandestinus Yeatman, 1964 Cyclops claudiopolitanus Daday, 1885 Cyclops clausii Lubbock, 1863 Cyclops clausii Poggenpol, 1874 Cyclops claviger O. F. Müller, 1785 Cyclops coecus Pratz, 1866 Cyclops coeruleus O. F. Müller, 1785 Cyclops colchidanus Borutsky, 1930 Cyclops columbianus Grassel, 1956 Cyclops communis Lindberg, 1938 Cyclops compactus G. O. Sars, 1909 Cyclops coronatus Claus, 1857 Cyclops crassicaudis G. O. Sars, 1863 Cyclops crassicaudoides Kiefer, 1928 Cyclops crassicornis O. F. Müller, 1785 Cyclops crinitus Graeter, 1910 Cyclops croaticus Krmpotic, 1924 Cyclops cunningtoni G. O. Sars, 1909 Cyclops curticaudus Dana, 1847 Cyclops curticornis O. F. Müller, 1785 Cyclops cyprinaceus (Shaw, 1789) Cyclops davidi Chappuis, 1922 Cyclops delachauxi Kiefer, 1925 Cyclops delphinus (O. F. Müller, 1785) Cyclops demetiensis Scourfield, 1932 Cyclops dengizicus Lepeshkin, 1900 Cyclops dentatimanus Marsh, 1913 Cyclops dentatus Rehberg, 1880 Cyclops dentatus Koch, 1844 Cyclops denticulatus Nicolet, 1849 Cyclops depressus Baird, 1837 Cyclops diaphanus Fischer, 1853 Cyclops diminuta Lindberg, 1937 Cyclops dimorphus Kiefer, 1934 Cyclops distans Kiefer, 1956 Cyclops distinctus Richard, 1887 Cyclops diversus (Kiefer, 1935) Cyclops divulsus Lindberg, 1956 Cyclops donnaldsoni Chappuis, 1929 Cyclops dubitabilis Kiefer, 1934 Cyclops dubius G. O. Sars, 1909 Cyclops dulvertonensis G. W. Smith, 1909 Cyclops dumasti Joly, 1883 Cyclops dybowskii Landé, 1890 Cyclops eboracensis Brady, 1902 Cyclops echinatus Kiefer, 1926 Cyclops ecornis Tilesius, 1819 Cyclops edax S. A. Forbes, 1890 Cyclops elegans Herrick, 1884 Cyclops elgonensis Kiefer, 1932 Cyclops elongatus Claus, 1863 Cyclops emini Mrázek, 1898 Cyclops entzii Daday, 1885 Cyclops euacanthus G. O. Sars, 1909 Cyclops ewarti Brady, 1888 Cyclops exiguus G. O. Sars, 1909 Cyclops exilis Coker, 1934 Cyclops exsulis Gauthier, 1951 Cyclops falsus Kiefer, 1929 Cyclops fasciacornis Cragin, 1883 Cyclops fedtschenkoi Ulyanin, 1875 Cyclops feuerborni Kiefer, 1933 Cyclops fimbriatus Fischer, 1853 Cyclops finmarchicus O. F. Müller, 1776 Cyclops fischeri Poggenpol, 1874 Cyclops flexipes Kokubo, 1912 Cyclops fluviatilis Herrick, 1882 Cyclops foliaceus (Linnaeus, 1758) Cyclops forbesi Herrick, 1895 Cyclops formosanus Harada, 1931 Cyclops fragilis Kiefer, 1926 Cyclops franciscoloi Brian, 1951 Cyclops frivaldszkyi Daday, 1885 Cyclops furcatus Baird, 1837 Cyclops furcifer Claus, 1857 Cyclops furi Kozhova & Pavlov, 1986 Cyclops fuscus Jurine, 1820 Cyclops gauthieri Green, 1963 Cyclops gemellus (Gurney, 1928) Cyclops geoffroyi Samouelle, 1819 Cyclops gibbus (Philippi, 1843) Cyclops gibsoni Brady, 1904 Cyclops gigas Claus, 1857 Cyclops glacialis Brady, 1910 Cyclops gnatho (Philippi, 1843) Cyclops gracilicornis Landé, 1891 Cyclops gracilis Lilljeborg, 1853 Cyclops graeteri Chappuis, 1927 Cyclops grandis Kiefer, 1935 Cyclops grandispinifer Lindberg, 1940 Cyclops gredleri Heller, 1871 Cyclops gyrinus S. A. Forbes, 1890 Cyclops hadjebensis Kiefer, 1926 Cyclops halepensis Chappuis, 1922 Cyclops hamatus Sovinsky, 1888 Cyclops harpacticoides Shmankevich, 1875 Cyclops haueri Kiefer, 1931 Cyclops heberti Einsle, 1996 Cyclops helgolandicus Rehberg, 1880 Cyclops helleri Brady, 1878 Cyclops horvathii Daday, 1885 Cyclops hungaricus Daday, 1885 Cyclops hutchinsoni Kiefer, 1936 Cyclops hypogeus Kiefer, 1930 Cyclops ignaeus Poggenpol, 1874 Cyclops igneus Poggenpol, 1874 Cyclops incertus Wolf, 1905 Cyclops indolusitanicus Lindberg, 1938 Cyclops inermis Tilesius, 1812 Cyclops infernus Kiefer, 1930 Cyclops ingens Herrick, 1882 Cyclops inopinatus (G. O. Sars, 1927) Cyclops inopinus Kiefer, 1926 Cyclops insectus S. A. Forbes, 1882 Cyclops insignis Claus, 1857 Cyclops intermedius Sovinsky, 1888 Cyclops isodactylus (Philippi, 1843) Cyclops jashnovi Streletskaya, 1990 Cyclops javanus Kiefer, 1930 Cyclops jeanneli Chappuis, 1929 Cyclops johnstoni Baird, 1834 Cyclops josephi Moniez, 1887 Cyclops juri Parveen, Mahoon & Saleem, 1990 Cyclops karamani Kiefer, 1932 Cyclops karvei Kiefer & Moorthy, 1935 Cyclops kaufmanni Ulyanin, 1875 Cyclops kentanensis Harada, 1931 Cyclops kieferi Chappuis, 1925 Cyclops kievensis Sovinsky, 1887 Cyclops kikuchii Smirnov, 1932 Cyclops kolensis Lilljeborg, 1901 Cyclops korostyschevi Sovinsky, 1888 Cyclops kozminskii Lindberg, 1942 Cyclops krillei Studer, 1878 Cyclops lacinulatus O. F. Müller, 1776 Cyclops lacunae Lowndes, 1926 Cyclops lacustris G. O. Sars, 1863 Cyclops ladakanus Kiefer, 1936 Cyclops laevimargo G. O. Sars, 1909 Cyclops landei Mahoon & Zia, 1985 Cyclops languidoides Lilljeborg, 1901 Cyclops languidulus Willey, 1925 Cyclops languidus (G. O. Sars, 1863) Cyclops lascivus Poggenpol, 1874 Cyclops laticauda Templeton, 1836 Cyclops latipes Lowndes, 1927 Cyclops latissimus Poggenpol, 1874 Cyclops laurenticus Lindberg, 1956 Cyclops learii Ulrich, 1902 Cyclops leewenhoekii Hoek, 1878 Cyclops leptopus Kiefer, 1927 Cyclops leuckarti Claus, 1857 Cyclops lilljeborgi G. O. Sars, 1918 Cyclops linjanticus Kiefer, 1928 Cyclops littoralis Brady, 1872 Cyclops lobulosus Ekman, 1905 Cyclops longicaudatus Poggenpol, 1874 Cyclops longispina Templeton, 1836 Cyclops longistylis Brady, 1907 Cyclops lubbocki Brady, 1869 Cyclops lucidulus Koch, 1838 Cyclops maarensis Vosseler, 1889 Cyclops macleayi Dana, 1847 Cyclops macruroides Lilljeborg, 1901 Cyclops macrurus G. O. Sars, 1863 Cyclops macuroides Lilljeborg, 1901 Cyclops madagascariensis Kiefer, 1926 Cyclops magniceps Lilljeborg, 1853 Cyclops magnoctavus Cragin, 1883 Cyclops magnus (Marsh, 1920) Cyclops malayicus Kiefer, 1930 Cyclops margaretae Lindberg, 1938 Cyclops margoi Daday, 1885 Cyclops marinus Prestandrea, 1833 Cyclops matritensis Velasquez, 1941 Cyclops mendocinus Wierzejski, 1893 Cyclops menzeli Kiefer, 1926 Cyclops meridianus Kiefer, 1926 Cyclops michaelseni Mrázek, 1901 Cyclops micropus Kiefer, 1932 Cyclops miles Nicolet, 1849 Cyclops miniatus Lilljeborg, 1901 Cyclops minimus Kiefer, 1933 Cyclops minnilus S. A. Forbes, 1893 Cyclops minuticornis O. F. Müller, 1785 Cyclops minutissimus Kiefer, 1933 Cyclops minutus Claus, 1863 Cyclops modestus Herrick, 1883 Cyclops moghulensis Lindberg, 1939 Cyclops monacanthus Kiefer, 1928 Cyclops monardi Perret, 1925 Cyclops mongoliensis Einsle, 1992 Cyclops mulleri Ferussac, 1806 Cyclops muscicola Menzel, 1926 Cyclops muscicolus Lastochkin, 1927 Cyclops nanus G. O. Sars, 1863 Cyclops naviculus Say, 1818 Cyclops navus Herrick, 1882 Cyclops nearcticus Kiefer, 1934 Cyclops necessarius Kiefer, 1926 Cyclops neglectus G. O. Sars, 1909 Cyclops neumani Pesta, 1927 Cyclops neymanae Streletskaya, 1990 Cyclops niceae Mann, 1940 Cyclops nigeriae Brady, 1910