New and recently described Gomphonema species (Bacillariophyceae) from Siberia

This paper reports on five species of the genus Gomphonema, which seem to be widespread at least in Siberia or in other regions, too. Due to their wide distribution their knowledge is of special importance. Three species are described as new (G. demersum, G. jergackianum and G. marvanii) based on light-(LM) and scanning electron microscopical (SEM) investigations. Important characters delimiting these species from similar taxa are discussed. For two recently described species (G. liyanlingae METZELTIN et LANGE-BERTALOT and G. khentiiense METZELTIN, LANGE-BERTALOT et NERGUI) ultramicorscopical details or SEM micrographs are presented for the first time and additional data on their distribution are given.