Nupela semifasciata (Bacillariophyceae), a new species from subtropical lotic environments in Western Paraná State, Brazil

During a survey on freshwater epilithic diatoms from subtropical lotic environments belonging to the Cascavel River microbasin, Paraná State, Brazil, we observed populations of a new Nupela Vyverman et Compère species. Morphological and meristic analyses were performed using light and scanning electron microscopy, resulting in the description of Nupela semifasciata sp. nov. This species is characterized by elliptic–lanceolate valves containing subcapitate apices in larger individuals and broadly rostrate–rounded apices in smaller ones, while the length/width ratio gradually decreases as the individuals become smaller. The central area unilaterally reaches the margin and always interrupts the row of areolae on the valve mantle. The valve mantle is externally composed of a second row of areolae near the apices. We cross–checked information with similar Nupela taxa, highlighting the main features that separate them. Nupela semifasciata was found in streams with acidic–neutral pH, low conductivity and low to high nutrient concentrations.