| Abstract from DBPedia | 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, 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. While early work indicated the group may not be monophyletic and early molecular phylogeny was ambiguous on this front, recent combined analyses of molecular and morphological data found support for monophyly in analyses with broadest taxon sampling. 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. While Myodocopa is restricted to marine environments, the Podocopida are also common in fresh water, and terrestrial species of are known from humid forest soils of South Africa, Australia and New Zealand. But all three major podocopid lineages, Cypridocopina, Darwinulocopina and Cytherocopina, have several representatives living in terrestrial habitats. 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. However, a large portion of diversity is still undescribed, indicated by undocumented diversity hotspots of temporary habitats in Africa and Australia. Of the known specific and generic diversity of nonmarine ostracods, half (1000 species, 100 genera) belongs to one family (of 13 families), Cyprididae. 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.貝虫（かいむし、学名: Ostracoda）または貝虫類（かいむしるい）は、甲殻類を大きく分けた節足動物の分類群の1つ。分類学上は貝虫綱とされる。貝形虫、カイミジンコ類などとも呼ばれ、カイミジンコ、ウミホタルなどが含まれる。全身が二枚貝のような殻で覆われ、一般に約1mmの小型甲殻類である。 外見的には同じ甲殻類のミジンコ類とカイエビ類に似ているが、これらは鰓脚類で、甲殻類の中で貝虫類とは別系統である。 (Source: http://dbpedia.org/resource/Ostracod) |
