Morphology and phylogeny of calcareous cyst-producing dinoflagellate Scrippsiella precaria Montresor & Zingone {Thoracosphaeraceae} from Korean coastal area

Abstract

Scrippsiella precaria was isolated from the Jinhae Bay, Korea. The monadoid cells were usually solitary and rarely in pairs, oval in shape, slightly dorso-ventrally compressed, 20.4-28.5 μm in length and 18.1-24.4 μm in width. The epitheca was conical and rounded apex, and the hypotheca was somewhat trapezoidal or some hemisphere. The nucleus was spherical to oval and located in the central part of the cell. Scanning electron microscope observation revealed that the monadoid cells have a Kofoidian plate formula of Po, X, 4', 3a, 7", 6C, 5S, 5"', 2"", and that many small pores are distributed on the thecal surface. Plates la and 3a were hexagonal shape however, plate 2a was rhombic shape and especially small size. Coccoid cells were spherical to oval in shape, yellow-green in color with a red accumulation body, and were covered with polygonal calcareous spines. Molecular phylogenetic analysis based on internal transcribed spacer and5.8s rDNA showed that S. precaria is nested within Scrippsiella sensu lato clade and closely related to S. irregularis and S. ramonii.