On the occurrence of Spirogyra maxima (Zygnematophyceae) in the Upper Paraná River floodplain

Abstract

Massive growth of Spirogyra Link was observed in multispecific banks of aquatic macrophytes in the Baía River, Upper Paraná River floodplain, in August 2019. In the laboratory and under optical microscopy, reproductive stages (conjugation) were observed in the collected specimens, which made it possible to determine the species taxonomically as Spirogyra maxima (Hassall) Wittrock. This species is characterized by the wide variation in the size of vegetative cells, spiral plastids arranged in up to nine ribbons and with small pyrenoids. Zygospores have lenticular morphology of the reticulated wall. The occurrence of this species represents a new citation for the Upper Paraná River floodplain.