Epithemia hirudiniformis and Related Taxa within the Subgenus Rhopalodiella subg. nov. in Comparison to Epithemia subg. Rhopalodia stat nov. (Bacillariophyceae) from East Africa

Abstract Epithemia hirudiniformis and three morphologically related taxa, described in Rhopalodia by O. Müller from material collected in East Africa at the end of the 19th and the beginning of the 20th century were re-evaluated and lectotypes designated. Rhopalodiella as a new subgenus is proposed which refines O. Müller's infrageneric classification and to which all these taxa belong. In addition, the type of Epithemia rhopala, described by Ehrenberg from Egypt, was studied to examine the assumed synonymy, introduced by Hustedt, with some of Müller's species. This study, using light and scanning electron microscopy, was not only based on historic material but also more recent material from Africa, including samples from the Island of Reunion from which the new species Epithemia vandevijveri is described. The distribution of Epithemia subg. Rhopalodiella, known to be restricted to tropical Africa, is discussed based on literature data and own observations. Corresponding to recent molecular-based studies, Rhopalodia is given a new status as subgenus.