Ostracods are amazing small crustaceans, which inhabit virtually all aquatic environments on Earth. The group is characterized by a body completely enclosed between two valves which in many species occur as calcified “shells”. Thus, they have a "seed"-like appearance, and therefore are also known by the term "seed shrimps" or "mussel shrimps". Ostracods range from warm waters of the tropics to very cold environments such polar seas and are found from intertidal zones to many thousands of metres depth in the deep sea They are also adapted to freshwater niches such as rivers, lakes and even temporary ponds. Most species reproduce sexually but some of them reproduce asexually by parthenogenesis.
Ostracods are generally tiny animals, with a body length mostly ranging from 0.2 mm to 2.0 mm. The planktonic genus Gigantocypris can, however, reach 32mm in length. Characteristically ostracods have eight pairs of appendages (though they can be fewer in number), which function mostly in feeding, locomotion and for sensory purposes.
Because ostracods have a calcified carapace they have a high preservational capacity. They are by far the most abundant arthropods in the fossil record, occurring in countless numbers at more or less all stratgraphic records from at least the Ordovician onwards. Their soft-parts have even been found in 450 million-year-old rocks. Ostracods have utility: they are used to date and correlate rock sequences world-wide, and are good palaeoenvironmental indicators, revealing information on, for example, palaeobathymetry, palaeosalinity and palaeoclimatic changes of our planet throuph time. Interestingly, ostracods have survived the 5 ‘big extinctions’ of life that have occurred over the last 540 million years, and have also survived in zero gravity for 4 months in the Russian Mir space station! For other interesting facts about ostracods see Williams et al. (2015).
The class encloses over 33,000 described species and subspecies (see Kempf Ostracoda Database for details), and many more species remain unknown to science. There are two subclasses with living representatives: Myodocopa and Podocopa. The first subclass is exclusive to marine environments, but occupies the benthos as well as the plankton, while podocopans occur in marine, brackish and freshwater environments and occupies almost exclusively benthos (but also the benthopelagic zone).
This World Ostracoda Database is part of the World Register of Marine Species (WoRMS), a global initiative to provide a register of all names of marine organisms living today (or extinct since a geologically short time). But the World Ostracoda Databasealso includes freshwater and fossil taxa.
The present database has the following objectives:

1. to provide an authoritative list of the world's Ostracoda taxa (species, genera, families…), with focus on the recent taxa, but also with information on fossils,
2. to provide a list of papers published on ostracods, and
3. to provide a base link to other online databases.