ostracod

raakkuäyriäinen Any of many small crustaceans, of the class Ostracoda, that resemble a shrimp enclosed in a bivalve shell.
1990, Anne Van Frausum, Karel Wouters, 39: Ostracoda from Holocene calcareous tufa deposits in southern Belgium: a palaeoenvironmental analysis, R. Whatley, C. Maybury (editors), Ostracoda and Global Events, http://books.google.com.au/books?id=I_pEO8MORRoC&pg=PA509&dq=%22ostracod%22%7C%22ostracods%22&hl=en&sa=X&ei=DhHBUuCcGc2ZlQXe_oDYBA&redir_esc=yv=onepage&q=%22ostracod%22%7C%22ostracods%22&f=false page 509,

Considering all the ecological data, there seems to be an evolution in the associations of ostracods throughout time.

This study has also shown that the fifth limb is most probably of thoracic origin and hence ostracods have only one pair of maxillae.

A number of parasites and epibionts have been reported from freshwater ostracods, including cestodes, protozoans, helminthes, peritrichs, and acanthocephalans (Griffits and Evans 1994).