Cochlodinium fulvescens sp. nov. (Gymnodiniales, Dinophyceae), a new chain-forming unarmored dinoflagellate from Asian coasts

Cellular morphology and the phylogenetic position of a new unarmored photosynthetic dinoflagellate Cochlodinium fulvescens Iwataki, Kawami et Matsuoka sp. nov. were examined by light microscopy and molecular phylogenetic analyses based on partial large subunit ribosomal DNA (LSU rDNA) and small subunit ribosomal DNA (SSU rDNA) sequences. The cells of C. fulvescens closely resemble C. polykrikoides, one of the most harmful red tide forming dinoflagellates, due to it possessing a cingulum encircling the cell approximately twice, a spherical nucleus positioned in the anterior part of the cell and an eyespot‐like orange pigmented body located in the dorsal side of the epicone, as well as formation of cell‐chains. However, this species is clearly distinguished from C. polykrikoides based on several morphological characteristics, namely, cell size, shape of chloroplasts and the position of narrow sulcus situated in the cell surface. The sulcus of C. fulvescens is located at the intermediate position of the cingulum in the dorsal side, whereas that of C. polykrikoides is situated immediately beneath the cingulum. LSU rDNA phylogenies indicated that C. fulvescens is clearly distinct from, but closely related to C. polykrikoides among dinoflagellates.