The Morphological, Genetic and Physiological Characteristics of a Benthic Dinoflagellate of the Genus <italic>Ostreopsis</italic> Isolated from Coastal Waters of the Northwestern Sea of Japan.

A previous molecular-genetic analysis of clonal cultures and single cells of <italic>Ostreopsis</italic> spp. that were isolated from Peter the Great Bay (the Sea of Japan) revealed three different genotypes according to the nucleotide sequences of ribosomal DNA (rDNA). Of these, <italic>Ostreopsis</italic> sp. 1 was earlier found only off the coast of Japan and described as being the most common and highly toxic. We have obtained further molecular evidence and have studied the morphological features of cells from one of the <italic>Ostreopsis</italic> strains with this genotype and some aspects of its growth at salinities of 24, 28, and 32‰. The results showed that in cells from the Russian coast of the Sea of Japan, the third apical (3') and the third precingular (3") plates do not adjoin one another, being separated by the elongated second apical (2') plate. Cells of <italic>Ostreopsis</italic> sp. 1 from the Russian coast are significantly larger than <italic>Ostreopsis</italic> sp. 1 cells with the same genotype from the coast of Japan. Salinity did not have a substantial effect on the growth of <italic>Ostreopsis</italic> sp. 1. The growth rate varied from 0.24 to 0.35 divisions per day, with maximum values at a salinity of 24‰. When salinity decreased to 24‰, the exponential growth phase was significantly extended and the maximum cell concentration doubled. [ABSTRACT FROM AUTHOR]