Two new Prestauroneis Bruder & Medlin (Bacillariophyceae) species from Zoige Wetland, Sichuan Province, China, and comparison with Parlibellus E.J. Cox.

摘要

We present light and scanning electron microscopy on two new species of Prestauroneis from the Zoige Wetland, Sichuan Province, China. Prestauroneisnenwai sp.nov. is rhomboid in shape with acutely rounded apices. Striae around the central area are more widely spaced than elsewhere on the valve, and distinct pseudosepta are present. This new species is distinguished from the two previously described species in this genus by the shape and size of the valves. Prestauroneislowei sp.nov. is more elliptical in outline, with barely protracted, broadly rounded apices. An indistinct pseudoseptum is present at each pole. This second new species is similar to Parlibellusprotracta, but differs in outline, especially in the degree to which the headpole is protracted. Some species similar to Prestauroneis have been included in Parlibellus, a genus of quite different morphology. We compare the differences between these two genera, and based on published observations of valve ultrastructure we propose two new combinations, Prestauroneisprotractoides (Hustedt) Q. Liu & Kociolek comb.nov. and Prestauroneisprotracta (Grunow ex Cleve) Q. Liu & Kociolek comb.nov. Assignment to Prestauroneis of other species in Parlibellus awaits future scanning electron microscopy studies. Although currently a small genus, Prestauroneis may be found across a wide spectrum of environments, from fresh to brackish/marine waters.