Morphology, taxonomy and distribution of the rare species Aulacoseira cataractarum (Hustedt) Simonsen (Bacillariophyta) in Russia

This scanning electron microscopy study was undertaken to reanalyze frustule samples of the centric diatom algae Aulacoseira cataractarum, collected earlier from a swamp in the Uzon volcanic caldera (Kamchatka). This species, under the name of Melosira cataractarum, was reported before from a number of waterbodies in Russia. Later it was transferred to the genus Aulacoseira Thwaites – A. cataractarum (Hustedt) Simonsen (Simonsen, 1979), and then – to the genus Pseudostaurosira (A.Grunow) D.M.Williams & F.E.Round, under the name of P. seudostaurosira cataractarum (Hustedt) Wetzel, Morales et Ector. In this study we specify perforation of intercalary bands, the shape of the valves and spines as well as the number of valve face and mantle areolae per stria and their shape. Based on the original and published data an extended diagnosis of P. cataractarum is presented. Scanning electron microscope images of frustules of the centric diatom algae.