Temporal range: Ordovician to Recent, 450–0 Ma
Scientific classification edit
Latreille, 1802
Subclasses and Orders

Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 70,000 species (only 13,000 of which are extant) have been identified,[1] grouped into several orders. They are small crustaceans, typically around 1 mm (0.039 in) in size, but varying from 0.2 to 30 mm (0.008 to 1.181 in) in the case of Gigantocypris. Their bodies are flattened from side to side and protected by a bivalve-like, chitinous or calcareous valve or "shell". The hinge of the two valves is in the upper (dorsal) region of the body. Ostracods are grouped together based on gross morphology, but the group may not be monophyletic;[2] their molecular phylogeny remains ambiguous.[3]

Ecologically, marine ostracods can be part of the zooplankton or (most commonly) are part of the benthos, living on or inside the upper layer of the sea floor. Many ostracods, especially the Podocopida, are also found in fresh water, and terrestrial species of Mesocypris are known from humid forest soils of South Africa, Australia and New Zealand.[4] They have a wide range of diets, and the group includes carnivores, herbivores, scavengers and filter feeders.

As of 2008, around 2000 species and 200 genera of nonmarine ostracods are found.[5] However, a large portion of diversity is still undescribed, indicated by undocumented diversity hotspots of temporary habitats in Africa and Australia.[6] Of the known specific and generic diversity of nonmarine ostracods, half (1000 species, 100 genera) belongs to one family (of 13 families), Cyprididae.[6] Many Cyprididae occur in temporary water bodies and have drought-resistant eggs, mixed/parthenogenetic reproduction, and the ability to swim. These biological attributes preadapt them to form successful radiations in these habitats.[7]


Ostracod comes from the Greek óstrakon meaning shell or tile. The word "ostracize" comes from the same root due to the practice of voting with shells or potsherds.[8]

Other Languages
العربية: صدفيات
беларуская: Ракушкавыя
català: Ostràcode
Cebuano: Ostracoda
čeština: Lasturnatky
Deutsch: Ostrakoden
español: Ostracoda
Esperanto: Ostrakodoj
euskara: Ostrakodo
فارسی: صدفیان
français: Ostracode
galego: Ostrácodos
한국어: 패충류
hrvatski: Dvoljušturci
Bahasa Indonesia: Ostracoda
interlingua: Ostracoda
italiano: Ostracoda
עברית: צדפונאים
Basa Jawa: Ostracoda
ქართული: ნიჟარიანები
latviešu: Gliemeņvēži
lietuvių: Kiautavėžiai
Nederlands: Mosselkreeftjes
日本語: 貝虫
norsk nynorsk: Muslingkreps
oʻzbekcha/ўзбекча: Chigʻanoqlilar
português: Ostracoda
română: Ostracode
русский: Ракушковые
Simple English: Ostracod
slovenščina: Dvoklopniki
українська: Черепашкові раки
Tiếng Việt: Ostracoda
Winaray: Ostracoda
中文: 介形綱