Spiniferodinium galeiforme, a new genus and species of benthic dinoflagellates (Phytodiniales, Pyrrhophyta) from Japan

Spiniferodinium galeiforme gen. et sp. nov. (Phytodiniales, Pyrrhophyta) occurs in sand on the shores of a subtropical island in Japan. The nonmotile vegetative phase reproduces by zoospores. The nonmotilecell is unicellular, photosynthetic, epilithic or epiphytic, with many ellipsoidal chloroplasts and typical dinokaryotic nucleus and possessing a helmet-shaped cell covering, which we have termed a ‘helmet shell’. The ‘helmet shell’ is transparent, rigid and covered by numerous small regularly distributed spines. The covering in the nonmotile state consists of an outer and inner component. The outer part is the ‘helmet shell’ proper. The inner part is structurally similar to that of other unarmored dinoflagellates. The cell covering of the motile stage consists of an outer shell building material (SBM) layer, an outer cytoplasmic (OC) layer and an inner layer whose components are the same as that of the nonmotile cell. The SBM layer contains shell building material which is cylindrical and crystalline. It contributes to the spine formation when the zoospore becomes nonmotile. The OC layer includes many single or double membrane-bound vesicles. This kind of spiny vegetative form has not been known in the Dinophyceae.