This study aimed to publish species belonging to the genus Cosmarium Corda of the periphytic community in three regions of the Rosana reservoir, southern Brazil. The samples were collected during the summer period and winter in the distinct regions to long of the axis the river-dam in the Rosana (Paranapanema River). The collected substrata, always in the littoral region and in all of the collection points, they were petioles of Eichhornia azurea Kunth. In the results were registered 48 species, distributed in fluvial, intermediary and lacustrine regions. Among these taxa, 45 were registered for the summer and 31 for the winter. Higher species richness occurred in the lacustrine region for both periods of collection. Cosmarium abbreviatum Raciborski var. minus (West & West) Krieger & Gerloff, C. granatum Brébisson ex Ralfs, C. pseudoconnatum Nordstedt, C. punctulatum Brébisson and C. quadrum Lundell var. minus Nordstedt occurred all regions were sampled in both periods.
desmids; periphytic algae; taxonomy
