ostracods

Ostracods, commonly known as seed shrimp, are a class of small crustaceans characterized by a calcified, two-part carapace that encloses the body. The shell, or valve, is typically bivalved and can be ornamented with ridges, nodes, or other sculpturing. Body size ranges from a few tenths of a millimeter to several millimeters, depending on species. Inside the carapace, the head and trunk bear the limbs adapted for feeding, locomotion, and sensing the environment, while the abdomen is usually reduced.

Ostracods are highly diverse and occupy a wide range of habitats. They can be planktonic, living in the water column, or benthic, dwelling in sediments, on submerged substrates, or among aquatic vegetation. Some species inhabit freshwater, others marine, and a few have adapted to terrestrial damp soils. Feeding modes vary and include detritivory, grazing on microalgae, filter feeding, and scavenging. Reproduction is primarily sexual in many species, but parthenogenesis occurs in some freshwater and other lineages, leading to populations composed largely of females in those cases.

The fossil record of ostracods is extensive, dating back to the early Cambrian period. Their mineralized carapaces fossilize readily, making them important in paleontology and biostratigraphy. Because different species tolerate different environmental conditions, ostracod assemblages are used to reconstruct past water temperatures, salinity, and other climatic factors in both marine and freshwater settings.

Ostracods are found worldwide and are common components of aquatic ecosystems. Their ecological versatility and rich fossil record have made them valuable indicators in earth science research as well as subjects of ongoing taxonomy and evolutionary studies.