Oithona is a planktoniccrustacean genus found in marine, brackish, fresh water environments. Oithona has been described as the most ubiquitous and abundant copepod in the world's oceans. It was first described by Baird in 1843 using the species Oithona plumifera as taxon type.
The following species are recognized:
Oithona aculeata Farran, 1913
Oithona alvarezi Lindberg, 1955
Oithona amazonica Burckhardt, 1913
Oithona aruensis Früchtl, 1923
Oithona atlantica Farran, 1908
Oithona attenuata Farran, 1913
Oithona australis Nishida, 1986
Oithona bjornbergae Ferrari F.D. & Bowman, 1980
Oithona bowmani Rocha C.E.F., 1986
Oithona brevicornis Giesbrecht, 1891
Oithona colcarva Bowman, 1975
Oithona cruralis Nishida, Tanaka & Omori, 1977
Oithona davisae Ferrari F.D. & Orsi, 1984
Oithona decipiens Farran, 1913
Oithona dissimilis Lindberg, 1940
Oithona erythrops Brady, 1915
Oithona fallax Farran, 1913
Oithona farrani (Brady, 1915)
Oithona flemingeri (Ferrari & Bowman, 1980)
Oithona fonsecae Ferrari & Bowman, 1980
Oithona fragilis Nishida, 1979
Oithona frigida Giesbrecht, 1902
Oithona gessneri Kiefer, 1954
Oithona hamata Rosendorn, 1917
Oithona hebes Giesbrecht, 1891
Oithona horai Sewell, 1934
Oithona linearis Giesbrecht, 1891
Oithona longispina Nishida, Tanaka & Omori, 1977
Oithona minuta Scott T., 1894
Oithona minuta Krichagin, 1877
Oithona nana Giesbrecht, 1893
Oithona nishidai McKinnon, 2000
Oithona oswaldocruzi Oliveira, 1945
Oithona pacifica (Nishida, 1985)
Oithona parvula (Farran, 1908)
Oithona plumifera Baird, 1843
Oithona pseudofrigida Rosendorn, 1917
Oithona pseudovivida Shuvalov, 1980
Oithona pulla (Farran, 1913)
Oithona robertsoni McKinnon, 2000
Oithona robusta Giesbrecht, 1891
Oithona rostralis Nishida, Tanaka & Omori, 1977
Oithona setigera (Dana, 1849)
Oithona similis Claus, 1866
Oithona simplex Farran, 1913
Oithona splendens Baird, 1843
Oithona tenuis Rosendorn, 1917
Oithona vivida Farran, 1913
Oithona wellershausi Ferrari F.D., 1982
Oithona abbreviata (Dana, 1849) (taxon inquirendum, listed as "Unbestimmbare Species" by Giesbrecht, 1892)
Oithona alia (Kiefer, 1935) accepted as Oithona rigida Giesbrecht, 1896 accepted as Dioithona rigida (Giesbrecht, 1896) (synonym according to Nishida, 1985)
Oithona canhanhae Oliveira, 1945 accepted as Oithona hebes Giesbrecht, 1891 (placed in synonymy by da Rocha, 1986)
Oithona challengeri Brady, 1883 accepted as Oithona setigera (Dana, 1849) (listed as synonym by Nishida, 1985)
Oithona helgolandica (Claus, 1863) accepted as Oithona similis Claus, 1866
Oithona neotropica Herbst, 1967 accepted as Oithona oswaldocruzi Oliveira, 1945 (placed in synonymy by da Rocha, 1986)