Morphology and phylogeny of an unarmoured dinoflagellate, Karlodinium jejuense sp. nov. (Gymnodiniales), isolated from the northern East China Sea

Abstract

An unarmoured dinoflagellate, Karlodinium jejuense sp. nov., was isolated from the northern East China Sea. The species was characterized by light, fluorescence, and scanning electron microscopy of laboratory cultures, as well as SSU rDNA, ITS region (ITS1-5.8S-ITS2) and LSU rDNA gene sequences. Cells were ellipsoid to oval, small-sized, 9.9&#8211 16.0&micro m in length and 6.2&#8211 12.7 &micro m in width. The chloroplasts were 7-10 in number and yellow-green in colour. The central nucleus was large, located in the center of the cell. The linear apical groove with outward thick rolled margins was very short, and there was no ventral pore. Small pores were irregularly distributed on the cell surface. The amphiesmal vesicles were hexagonal and pentagonal. Karlodinium jejuense was morphologically similar to K. ballantinum but differed in cell surface characteristics and swimming pattern. The partial LSU sequence of K. jejuense differed by 3.7&#8211 4.1% from that of K. ballantinum. Molecular phylogenetic analyses of multi-gene sequences revealed that K. jejuense was an independent species nested within the Karlodinium clade. Phylogenetic analysis based on partial LSU rDNA gene sequences indicated that K. jejuense was most closely related to K. gentienii and K. ballantinum.ITS region (ITS1-5.8S-ITS2) and LSU rDNA gene sequences. Cells were ellipsoid to oval, small-sized, 9.9&#8211 16.0&micro m in length and 6.2&#8211 12.7 &micro m in width. The chloroplasts were 7-10 in number and yellow-green in colour. The central nucleus was large, located in the center of the cell. The linear apical groove with outward thick rolled margins was very short, and there was no ventral pore. Small pores were irregularly distributed on the cell surface. The amphiesmal vesicles were hexagonal and pentagonal. Karlodinium jejuense was morphologically similar to K. ballantinum but differed in cell surface characteristics and swimming pattern. The partial LSU sequence of K. jejuense differed by 3.7&#8211 4.1% from that of K. ballantinum. Molecular phylogenetic analyses of multi-gene sequences revealed that K. jejuense was an independent species nested within the Karlodinium clade. Phylogenetic analysis based on partial LSU rDNA gene sequences indicated that K. jejuense was most closely related to K. gentienii and K. ballantinum.