ULTRASTRUCTURE OF THE DINOFLAGELLATE PERIDINIUM CINCTUM F. OVOPLANUM. I. VEGETATIVE CELL ULTRASTRUCTURE

Vegetative cells of Peridinium cinctum f. ovoplanum have a dense cytoplasm containing those organelles characteristic of eukaryotic cells. Thecal plates have a fibrillar substructure with numerous 200-nm pores. Chloroplasts are radially arranged and contain a simple internal pyrenoid. An eyespot is associated with the chloroplast. The large, centrally located nucleus contains over 100 chromosomes dispersed in a granular nucleoplasm. Chromosomal bands with a periodicity of 86 nm are present perpendicular to the long axis of the chromosome. Numerous chromosomes are attached to the nuclear envelope. Peridinium cinctum vegetative cell morphology is compared to other dinoflagellates examined.