Ultrastructure of a Marine Dinoflagellate, Peridinium quinquecorne Abe (Peridiniales) from South Africa with Particular Reference to its Chrysophyte Endosymbiont

The micro-morphology and the ultrastructure of a marine dinoflagellate, Peridinium quinquecorne Abe were studied. The dinoflagellate shows a wide range of morphological variation, including cell shape and length of the antapical spines. The thecal plate arrangement is: Pp, x, 3’, 2a, 7”, 5c, 5’”, 2“” 4s. Detailed study of the sulcus and the cingulum, which was not undertaken by the original author was carried out. The ultrastructural investigation revealed that all the chloroplasts belong to an endosymbiotic alga which is separated from the host cytoplasm by a single unit membrane. The host cytoplasm (dinokaryotic cytoplasm) revealed typical dinoflagellate organization. The eyespot is bounded by a triple membrane and is located in the host cytoplasm. The structure of the endosymbiont is simple and contains only a eukaryotic nucleus, mitochondria, dictyosomes and chloroplasts. The ultrastructural features of the chloroplasts suggest a chrysophyte affinity for the endosymbiont. © 1991 Walter de Gruyter.