The Ostracoda are a Subclass of small crustaceans (living forms range from 0.3-30 mm long) which occur in particularly every aquatic environment. In today's oceans they are found from the abyssal depths to the shoreline. They also inhabit estuaries, lagoons, freshwater lakes, ponds and streams, salt lakes, hot springs, damp vegetation and even the water which collects in bromeliad leaf-bases. Ostracods may be free-swimming for all or part of their life-cycle, or, more commonly, are benthonic, living among aquatic plants or crawling on or through the sediment. A number of interstitial forms are known. Ostracods display a variety of feeding habits; some are filter-feeders, others are scavengers, detritivores, herbivores or predaceous carnivores. A few species are parasitic or commensal on other crustaceans, polychaete worms and echinoderms.
The most distinctive feature of the Ostracoda is the calcareous bivalved carapace which can totally envelop the body and limbs, but from which various appendages are protruded for locomotion, feeding and reproduction.
The word ostracod is derived from the Greek word ostrakon ('a shell'); this shell or carapace has numerous morphological characters which allow taxonomic and phylogenetic studies to be made on living and fossil specimens.
The general structure of the Ostracoda is described in the chapter morphology.
Small ostracods (<700 µm) are not described on this CD-ROM. The following small species occur in the North Sea area (for a description and a key to the species see Athersuch et al., 1989):
Bonnyannella robertsoni (Brady, 1868)
Callistocythere badia (Norman, 1862)
Callistocythere littoralis (Muller, 1894)
Callistocythere murrayi Whittaker, 1978
Cytherois fischeri (Sars, 1866)
Cytherois pusilla Sars, 1928
Cytherois stephanidesi Klie, 1938
Cytheropteron depressum (Brady & Norman, 1889)
Cytheropteron dorsocostatum Whatley & Masson, 1980
Cytheropteron nodosum Brady, 1868
Cytherura gibba (O.F. Müller, 1785)
Elofsonia baltica (Hirschmann, 1909)
Elofsonia pusilla (Brady & Robertson, 1870)
Eucythere anglica Brady, 1868
Eucythere declivis (Norman, 1865)
Hemicytherura cellulosa (Norman, 1865)
Hirschmannia viridis (O.F. Müller, 1785)
Leptocythere baltica Klie, 1929
Leptocythere lacertosa (Hirschmann, 1912)
Leptocythere porcellanea (Brady, 1869)
Leptocythere psammophila Guillaume, 1976
Leptocythere tenera (Brady, 1868)
Loxoconcha elliptica Brady, 1868
Loxoconcha rhomboidea (Fischer, 1855)
Muellerina abyssicola (Sars, 1866)
Nannocythere pavo (Malcomson, 1886)
Neocytherideis subulata (Brady, 1868)
Palmenella limicola (Norman, 1865)
Palmoconcha guttata (Norman, 1865)
Palmoconcha laevata (Norman, 1865)
Paracytheridea cuneiformis (Brady, 1868)
Paracytherois flexuosa (Brady, 1867)
Paradoxostoma abbreviatum Sars, 1866
Paradoxostoma nealei Horne & Whittaker, 1985
Paradoxostoma normani Brady, 1868
Paradoxostoma porlockense Horne & Whittaker, 1985
Paradoxostoma pulchellum Sars, 1866
Paradoxostoma robinhoodi Horne & Whittaker, 1985
Paradoxostoma trieri Horne & Whittaker, 1985
Pseudocythere britannica Horne, 1986
Sagmatocythere multifora (Norman, 1865)
Sahnicythere retroflexa (Klie, 1936)
Sclerochilus abbreviatus Brady & Robertson, 1869
Sclerochilus gewemuelleri Dubowsky, 1939
Sclerochilus hicksi Athersuch & Horne, 1987
Sclerochilus truncatus (Malcomson, 1886)
Semicytherura acuticostata (Sars, 1866)
Semicytherura angulata (Brady, 1868)
Semicytherura cornuta (Brady, 1868)
Semicytherura nigrescens (Baird, 1838)
Semicytherura sella (Sars, 1866)
Semicytherura simplex (Brady & Norman, 1889)
Semicytherura striata (Sars, 1866)
Semicytherura tela Horne & Whittaker, 1980
Semicytherura undata (Sars, 1866)
Urocythereis britannica Athersuch, 1977
Xestoleberis aurantia (Baird, 1838)
Xestoleberis labiata Brady & Robertson, 1874
Xestoleberis nitida (Liljeborg, 1853)