A re-investigation of Otto Müller's Cymatopleura taxa (Bacillariophyta) from East Africa

Background – Otto Müller described seven varieties and forms of Cymatopleura solea from material from Central and East Africa. A re-investigation of the original material studied by Müller allowed us to lectotypify these taxa and describe another as new to science. Methods – Permanent diatom slides from original samples collected by Dr. Fülleborn in 1899 and 1900, and deposited at the Botanic Garden and Botanical Museum Berlin, Dahlem (B) were made. Additionally, material from Lake Victoria collected during the Third Tanganyika expedition conducted by Dr. Cunnington in 1904–1905, and kept at The National History Museum London (BM) were studied. Investigations were carried out using light microscopy and where possible also with scanning electron microscopy. Key results – Although Cymatopleura solea var. subconstricta and its forms major and minor are invalid, illustrations of Müller's concepts are shown and the taxon Cymatopleura comperei was described as new. On the other hand, the taxonomic entities var. clavata, var. laticeps and var. rugosa are redefined and raised to species rank: Cymatopleura clavata, C. laticeps and C. rugosa respectively. Additional morphological descriptions, based on light and scanning electron microscopy, are given for all these taxa where appropriate and their African distribution as based on literature and our own observations. In addition, the original slide of Cymatopleura nyansae, described from Central Africa by West, is also illustrated and discussed, firstly because it resembles the Cymatopleura laticeps valves which we observed in one of the historic samples from Lake Malawi examined by Müller, and secondly because often erroneous concepts of this taxon are present in the African literature