Sphaerocavum, a new genus of planktic Cyanobacteria from continental water bodies in Brazil

During the survey of planktic Cyanobacteria from Sao Paulo State some colonial specimens similar to Microcystis were isolated from two different reservoirs. However, they revealed to have cell division on two planes in successive generations and distinct colonial morphology. Observation of preserved nature material from the same and other localities, including one sample from Uruguay, enabled detailed study of these chroococcal Cyanobacteria and the proposal of a new genus and species - Sphaerocavum brasiliense. The life cycle and other phenotypic features are described and illustrated both in culture and field material. Its taxomonic position is discussed based on our data and two new combinations are proposed in this genus: S. leloupii (KUFF.) AZEV. et SANT' ANNA and S. microcystiforme (HIND.) AZEV. et SANT' ANNA. Physico-chemical data on the water bodies studied and geographical distribution are given.