Composition and distribution of rotifers in Rio de Janeiro State: a first assessment through freshwater ecoregions

The species richness is an essential component of biodiversity metrics and an ecological indicator for setting conservation actions. Phylum Rotifera consists of a specious group of conspicuous and minute animals, mainly in freshwater environments. In the Neotropical region, the knowledge of the biodiversity of rotifers is incomplete, with outdated and geographically restricted information. In this regard, we present a comprehensive inventory of rotifers from freshwater ecoregions in Rio de Janeiro. From the literature review and active surveillance, we detected 238 spp.; among these, 39 were previously unknown to the State. We also preliminarily examine the potential use of Rotifera for ecoregions delimitation. The extrapolated number of species shows an increasing richness for the Paraiba do Sul and Fluminense ecoregions, which were also significantly different regarding species composition. Registers from the Ribeira de Iguape and Northern Mata Atlantica ecoregions are still lacking in the State. We believe that future survey efforts will undoubtedly reveal additional records and taxa improving our understanding of biogeographical patterns such as dispersal and biological invasions. Ultimately, support future conservation policies and the potentialities of this group for ecoregion delimitations.