Rotifer assemblages (Rotifera: Eurotatoria) of the floodplain lakes of Majuli River Island, the Brahmaputra river basin, northeast India

Our plankton and semi-plankton collections from twelve floodplain lakes (beels) of Majuli River Island, Upper Assam reveal 124 rotifer species (32 genera and 17 families); these merit biodiversity value as ~52.0% and ~30.0% of species, ~68.0 and ~45.0% of  genera and ~74.0 and ~65.0% of the families of the Phylum known from northeast India (NEI) and India, respectively. Two species are new to India with Trichocerca uncinata as new record to the Oriental region.  Eleven species are new to the study area and we provide an updated list (144 species) for following meta-analyses of Majuli Rotifera. Biogeographically important elements include one Australasian, four Oriental, four Palaeotropical and one cosmo (sub) tropical species while several species are of regional distribution interest. The rotifer fauna is predominantly tropical and Lecanidae > Lepadellidae collectively include ~53.0% species but it records paucity of Brachionus species. Individual beels record total richness of 60-100 (77 ± 12) species, monthly richness between 24 ± 7-34 ± 7 species and maximum up to 54 species/sample. The results are characterized by high community similarities (59.7-90.4% vide Sí¸rensen's index), more rotifer homogeneity amongst beels, lack of any pattern of temporal richness variations and much limited influence of abiotic parameters.