New or otherwise interesting desmid taxa from the Bangweulu region (Zambia). 3. Genus Cosmarium (Desmidiales)

Background and aims – In a third contribution to the desmid flora of the Bangweulu wetlands in Zambia a selection of species from the genus Cosmarium is discussed for their taxonomy and geographical distribution.Methods – Samples were collected from Lake Bangweulu and adjacent swamps as well as from Lake Wakawaka. Collection was by squeezing submerged plant material or using a plankton net.Key results – Eleven taxa are described as new to science: Cosmarium bangweuluense, C. bidentulum, C. binodosum var. thomassonii, C. campanuliforme, C. connatoides, C. cunningtonii var . luxuriosum, C. lindiae, C. luapulaense, C. mitra, C. pseudoredimitum and C. subligoniforme. Two taxa, C. binerve var. elongatum and C. taxichondrum var. ambadiense, were raised in rank and provided with new names: C. binervoides and C. binodosum, respectively.Conclusions – All taxa discussed, except C. binervoides, have an exclusive African distribution. Quite a number of Cosmarium species encountered in the present study is marked by a cell wall sculpture consisting of prominent, scattered tubercles, those located just below the apex often being much bigger than the other ones. Possibly, this morphological feature may be considered one of the characteristics of the African Cosmarium flora