Genus Gyrosigma in Japan

Abstract

This is the first comprehensive report on Japanese Gyrosigma spp. with special reference to their taxonomy and distribution. They are very conspicuous in permanent slides because usually they have large valves with characteristic shapes. However they have not been well studied probably because of their paucity in most samples. In total 30 taxa were identified from samples collected from various localities throughout Japan. The following five taxa are newly reported from Japan: G. acuminatum var. curta, G. acuminatum var. lacustre, G. plagiostomum, G. simile, and G. spencerii var. curvula.