Cyst-motile stage relationship, morphology and phylogeny of a new chain-forming, marine dinoflagellate Grammatodinium tongyeonginum gen. & sp nov. from Korea

A new phototrophic dinoflagellate, Grammatodinium tongyeonginum gen. & sp. nov., was established by incubating resting cysts collected from surface sediment samples from Tongyeong coastal area, Korea. The resting cysts were ovoid with a large reddish pigment body and surrounded with a thick mucous layer that incorporated attached detritus particles. The vegetative cells were 24.6-40.9 mu m long and 16.4-27.3 mu m wide. The cell surface was covered with prominent longitudinal equidistant furrows. The cingulum was narrow and descended two to eight times its width. The nucleus was located at the central part of the epicone. The peripheral chloroplasts were usually granular and yellow-green in culture and were distributed along the rim of the cingulum. The horseshoe-shaped apical groove ran from the end of the sulcal extension anticlockwise around the apex. The distal end of the apical groove was located next to the extension of the sulcus and more to the ventral side than the proximal end. Molecular phylogenetic analysis using small subunit ribosomal DNA (SSU rDNA) gene sequences revealed that G. tongyeonginum was allied with the Cucumeridinium species. Large subunit ribosomal DNA (LSU rDNA) sequences revealed that G. tongyeonginum formed a clade distantly related to the other genera of Gymnodiniales. The combination of morphological characteristics with molecular phylogenies distinguished the present species from other genera within Gymnodiniales.