New planktic species of Kirchneriella Schmidle (Chlorophyceae, Selenastraceae) from Brazilian freshwaters

New planktic species of Kirchneriella Schmidle (Chlorophyceae, Selenastraceae) from Brazilian freshwaters. In the samples collected from an artificial lake, located in the metropolitan region of Sao Paulo, an interesting algal population morphologically similar to Kirchneriella Schmidle was found. The crescent-shaped cells were oriented, inside the colony, with their convex faces toward the periphery of the colony resembling those of K. roselata Hindak. However, the remaining portions of the mother cell wall with more or less radial arrangement similar to the connective mucilaginous threads of the genus Selenodictyon Uherkovich & Schmidt ex Comas & Komarek were also observed. After further studies based on light microscope, the studied material proves to be morphologically distinguishable from K. roselata, although it never forms rosette-like groups, which are typical in K. roselata. The remaining parts of the mother cell wall more or less radially disposed near the cells (autospores just released from the mother cell wall) are not connective threads. Thus, a new species, K. brasiliana, is described in this paper. According to literature, the main diagnostic feature of Selenodictyon is the crescent-shaped cells attached by their concave faces to mucilaginous stalks like in Dictyosphaerium; however, remaining portions of the mother cell wall more or less radially oriented were also formed in some Kirchneriella populations. Therefore, the authors consider that such feature could be misinterpreted as connective mucilaginous threads, which raises doubts regarding the validity of Selenodictyon.