Abstract:The type material of Achnanthidium lanceolatum (transferred in 1999 to the genus Planothidium) is investigated to reveal the identity of several Planothidium populations from the Antarctic Region. The morphology and the ultrastructure was analysed using light and scanning electron microscopy. The results of this analysis revealed the presence of two so far undescribed Planothidium species in the investigated Antarctic material. Both species are described as new to science: P. rostrolanceolatum Van de VijVer, KopaloVá et zidaroVa sp. nov. and P. subantarcticum Van de VijVer et c.e.Wetzel sp. nov. The new species can be differentiated based on differences in valve outline and the shape and size of the central area. Planothidium lanceolatum is formally lectotypified. Notes on the ecology and distribution of the new Antarctic species are added.
Background and aims -The limnoterrestrial and aquatic diatom flora of the entire Antarctic Region (sub-Antarctic islands, Maritime Antarctic Region, Antarctic Continent) is currently under revision. One of the genera that still needed a thorough analysis is the genus Halamphora, recently split off from Amphora. Halamphora species are a typical constituent of the lake diatom flora in the Antarctic region. Methods -Using both Light Microscopical (LM) and Scanning Electron Microscopical (SEM) techniques, the morphology of a large number of Halamphora taxa, present in the samples from the Antarctic Region, has been analysed. Each taxon is properly described, illustrated and compared with other morphologically similar Halamphora taxa, known worldwide. Key results -A total of seven Halamphora taxa has been found. Two taxa could be identified using the currently available literature: Halamphora veneta (Kütz.) Levkov and H. oligotraphenta (Lange-Bert.) Levkov. Five new Halamphora species are described:
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