Further Sem Study of Marine Dinoflagellates: The Genusostreopsis(dinophyceae)1

This paper presents a comprehensive examination of the taxonomy of the genusOstreopsisSchmidt. The morphology of six species of marine dinoflagellates,Ostreopsis siamensisSchmidt 1902.Ostreopsis lenticularisFukuyo 1981,Ostreopsis ovataFukuyo 1981,Ostreopsis heptagonaNorris, Bomber, et Balech 1985,Ostreopsis mascarenensisQuod 1994, andOstreopsis labensFaust et Morton 1995 from three geographical regions (Japan, Southwest Indian Ocean, and the Caribbean) and three marine habitats (sand, water column, and macroalgal surfaces) are described from scanning electron micrographs. Differences in the following morphological characteristics differentiated the species: cell shape and size, and ornamentation of the epitheca, cingulum, and hypotheca. The thecal plate formula of the sixOstreopsisspecies is Po,3′, 7″, 6C, 6S?, Vp, Rp, 5′″, 1p, 2″″, with differences in thecal plate size and shape. The cingulum in ventral view has two prominent structures: a ventral plate (Vp) with a ventral pore (Vo) and a ridged plate (Rp) that distinguishesOstreopsisspecies from any other dinoflagellate taxa. This paper also includes ecological and toxicity information regarding the sixOstreopsisspecies.