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Three Surirella taxa described by O. Müller from material collected at the beginning of the 20th century in Lakes Malawi and Malombe were re-evaluated, and lectotypes are assigned from the original material. One infraspecific taxon, S. nyassae var. sagitta, was synonymized with the nominate variety of S. nyassae and one forma, S. malombae f. acuta, was synonymized with S. malombae. As S. malombae is very rare in the original material from Lake Malombe, an epitype was also assigned from material collected at the end of the 19th century in Lake Victoria. Light and scanning electron microscopic information is given for these two taxa and their distribution in Africa and their habitat preference is summarized from the literature. A third closely related taxon which was regularly observed in Lake Tanganyika is here described as S. chepurnovii sp. nov.
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Surirella engleri, including its four original infraspecific taxa, was studied and typified using historical East African material from which Otto Müller described more than 100 new diatom taxa at the beginning of the 20th century. Considerable outline variation was found, in agreement with the results of experimental cultures carried out in the late 1980's on material from the northern basin of Lake Tanganyika. This variation supported the abandonment of taxonomic recognition of the four infraspecific taxa proposed by Müller. SEM analyses of this taxon from the original Lake Malombe material and from the recent Lake Tanganyika material showed some minor differences. The past and current distribution of this taxon which is endemic to Tropical Africa was summarized
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Four diatom taxa from East Africa, Surirella ovalis var. apiculata, S. ovalis var. apiculata f. minor, S. fasciculata and S. olungensis are discussed. The species were observed in material sampled by Fülleborn at the beginning of the 20th century and formerly studied and named - except the last - by O. Müller. The first two taxa were described from a sample of a hot spring near Utengule (Tanzania) and from Lake Rukwa respectively. Surirella fasciculata, related to the previous ones, was described from Lake Ngozi (Tanzania). Besides the translation of the original description, lectotypes and/or epitypes were designated and their distribution given based on literature. A new taxon, also related to Surirella ovalis, was observed in a sample from the Olunga river (Tanzania) and is here described as a new species: Surirella olungensis. Besides this new taxon, some aberrant forms were observed in the same historical sample
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Surirella bifrons var. intermedia O.Müll. and Surirella fuellebornii O.Müll., including its infraspecific taxa, were re-evaluated using historical East African material collected in the early 20th century from which Otto Müller described more than 100 new diatom taxa. In addition, material from the Hustedt Diatom Collection together with material collected during the past decades in the region of the African Great Lakes was studied. The investigation of the original material of Surirella bifrons Ehrenb. in the Ehrenberg Collection allowed us to elevate Surirella bifrons var. intermedia to species rank: Surirella kusberi nom. nov. The variation observed in the material studied supported the abandonment of taxonomic recognition of Surirella fuellebornii f. subconstricta O.Müll. and var. constricta O.Müll. On the other hand, var. tumida Hustedt and var. elliptica O.Müll. are here elevated to species rank: Surirella crawfordii nom. nov. and Surirella friedelhinziae nom. nov. respectively. Finally, Surirella fuellebornii var. worthingtonii H.Bachm. was found to belong within the variability of Surirella malombae O.Müll.
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Frustulia --- lectotypification --- Bacillariophyta = Diatoms = Diatomeae
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