Intracoelomic parasitic Sporozoa in the burrowing spatangoid echinoid Echinocardium cordatum: coelomocyte reaction and formation of brown bodies

Abstract

Echinocardium cordatum frequently harbours in its coelomic cavity the protozoan parasite Lithocystis schneideri. Motile stages of this gregarine (trophozoites and gamonts) may be surrounded by echinoid coelomocytes which show a peculiar transformation of their shape (i.e. each cell develops a single spine-like extension giving a pincushion aspect to the parasite). Encysted stages of the gregarine (gametocysts and sporocysts) are found mostly within brown bodies. Brown bodies are particular mesothelium-covered formations occurring usually in the coelomic cavity of E. cordatum. It is suggested that brown bodies naturally originate from detached fragments of mesenteries. © 1984 Biologische Anstalt Helgoland.