New data on morphology of some widespread and rare pennate diatoms (Bacillariophyta)

This electron microscopy study of new for the Volgograd Region (Russia) Anomoeoneis sphaerophora f. sculpta, Gyrosigma wansbeckii, and Pleurosigma elongatum from mineralized tributaries (Bolshaya Samoroda, Lantsug and Khara) of the hyperhaline Lake Elton provides new data on the variability of quantitative diagnostic characteristics (valve length, number of striae and areolae in 10 μm) and some morphological elements (raphe and areolae). For Anomoeoneis sphaerophora f. sculpta, false areolae were found on the external valve surface, it was shown for the first time that the raphe ends are bent towards the primary side of the valve as well. For Gyrosigma wansbeckii, data on the areolae number in 10 μm are presented for the first time. The range of length and width of Pleurosigma elongatum valves, as well as the number of striae and areolae in 10 μm, has been expanded.