ULTRASTRUCTURE OF THE 'ZOOXANTHELLA' ENDODINIUM CHATTONII IN SITU*

Studies on the ultrastructural morphology of Endodinium chattonii Hovasse reveal new taxonomic characters which support the generic separation of this alga and the only other completely described symbiotic dinoflagellate, Symbiodinium microadriaticum Freudenthal. Of interest is the presence of an amphidinium-like pyrenoid and an un- usual chloroplast structure not normally associated with dinofiagellates. The taxonomic significance of these observations is discussed in relation to other symbiotic and free- living species. A revision of the taxonomy of symbiotic dinofiagellates is proposed.