Contribution to the Diversity of World Bacillariaceae: Two New Nitzschia Taxa.

During a biological survey carried out in a high-altitude saline lake of the Bolivian Altiplano and in Türkmenbaba plateau in Sakarya river catchment in Kütahya and Korudere and Havuzdere streams in Marmarean river catchment in Yalova, Turkey, two unknown Nitzschia species were found in various population densities. Detailed light and scanning electron microscopy observations allowed their description as taxa new to Science. Differential diagnostic criteria with respect to similar taxa, together with ecological and biogeographical implications of these findings, are briefly discussed. The most noteworthy feature in N. tortuosa sp. nov. is the pervalvar twist seen at poles, well discernible in scanning electron microscopy (SEM), whereas N. seblae sp. nov. resembles N. tropica but presents broader valves and lower striae and fibulae densities. [ABSTRACT FROM AUTHOR]