Ostracoda or ostracods or ostracodes are crustaceans like crabs and lobsters. The animal has 7 pairs of appendages, specialized for different tasks. The animal lives inside a carapace made of two valves. They shed the carapace seven times during life growing a new larger one each time. They are sexually dimorphic - males and females are different shapes.

They can live in freshwater, brackish or marine environments. The freshwater ones tend to be bean shaped, with no hinge and thin, smooth valves. Marine ostracods tend to have thicker ornamented valves.

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