A new araphid diatom genus Psammoneis gen. nov (Plagiogrammaceae, Bacillariophyta) with three new species based on SSU and LSU rDNA sequence data and morphology

摘要

Five strains of a hitherto undescribed diatom genus, Psammoneis, were established from Japanese and Senegalese marine benthic samples. The strains were analysed using nuclear-encoded sequence markers and morphometric parameters of their silica frustules. Valves of all strains show a sternum with striae perpendicular thereupon, typical for pennate diatoms. They possess apical pore fields and lack a raphe, typical for araphids, but also rimoportulae. Areolar occlusions are not prominent and often appear to be totally absent. Sequence comparison of both the SSU rDNA and the D1/D2 region of the LSU rDNA revealed that the strains group into three markedly distinct genotypes. The strains from different genotypes were also distinguishable by a principal component analysis using four morphometric variables measured on the external valve surface. They are described as three new species in a new genus Psammoneis: P. japonica, P. pseudojaponica and P. senegalensis. Molecular phylogenies support placement of the genus Psammoneis as a member of the Plagiogrammaceae. Our observations on frustule Fine structures and the addition of Psammoneis to the family alter the circumscription of the family Plagiogrammaceae. Therefore, we provide an emended description of the family.