On the morphology and taxonomy of Parlibellus Crucicula (Bacillariophyta)

Abstract

A study of the phytoplankton of the water bodies and watercourses in the Yarayakha River and Naduiyakha River basins (the Yamal Peninsula) has revealed a wide morphological variability of the quantitative diagnostic features in Parlibellus crucicula: valve length and width, the number of striae and areolae in 10 μm, and the stria density in the middle part of the valve. A number of the features (raphe structure, presence of pseudosepta, and obliquely oriented oval areolae) typical for the genus Prestauroneis have been found in Parlibellus crucicula. This makes it possible to define this species as belonging to the genus Prestauroneis and to form a new combination, Prestauroneis crucicula (W. Smith) Genkal et Yarushina comb. nov.