Halamphora saxonica sp. nov. (Bacillariophyceae) from lakes in lignite-mining area in Saxony, Germany

摘要

Halamphora saxonica sp. nov. is described from two lakes, Ammelshainer See and Harthsee, Germany. The morphology of this species is examined in detail using both light and scanning electron microscopy and is compared with similar species. The species is characterized by semi-elliptical to semi-lanceolate valves with weakly protracted and ventrally bent apices, narrow axial and central areas, curved raphe branches located on a raphe ledge and strongly dorsally deflected proximal and distal raphe fissures. Internally, the raphe distally terminates with small helictoglossae, while the proximal raphe endings are simple without central fused helictoglossae. Halamphora saxonica resembles H. chilensis with respect to valve outline, stria and areola morphology, but can be differentiated by valve and frustule size, the presence of a raphe ledge and the shape of the proximal raphe fissures. Based on its features, H. saxonica belongs to the genus Halamphora although a few characters (raphe structure) might point to an intermediate position between Halamphora and the subgenus Diplamphora in the genus Amphora sensu lato. The generic limits of the genus Halamphora and its relationship with sections of Amphora are discussed.