Recherches sur un protiste, parasite nouveau de l'huître plate des côtes françaises

Following a number of mortalities reported on the flat oyster farms of the Ile Tudy in June 1979, a Protiste, a parasite then unknown in France, was found in the sick oysters. Located mainly in the connective tissue and the branchial epithelium, this parasite is associated with tissue damage. It can be either of a free type or of an intracellular type, both corresponding to small size cells (2 to 3 µm) and displaying, next to their core, one or two mitochondrion and some structured electron-dense particles. Moreover, different mitosis stages, with nuclear membrane persistence, have been observed. These ultrastructural characteristics show some similarities and differences with the Haplosporidies and Marteilia groups.