The biodiverse rotifers (Rotifera: Eurotatoria) of the Majuli River Island – an alluvial floodplain of Assam state (northeast India) and the largest river island

Our assessment of Rotifera biodiversity of the floodplain wetlands of the Majuli River Island of the Brahmaputra basin of Assam state of northeast India (NEI) reveals total 175 species belonging to 39 genera and 19 families. The rich and diverse assemblage vis-à-vis diversity of the phylum known from India, NEI and Assam categorizes the Majuli as one of the megadiverse Rotifera region of India. The biodiverse Rotifera is hypothesized to habitat diversity of the Majuli wetlands with varied aquatic macrophytes, location of the study areas under the ‘Indo-Burmese biodiversity hotspot’ and the ‘Rotiferologist effect’, and merit conservation interest in light of extinction threat of this alluvial floodplain. One species each is new to the Indian sub-region and NEI, 29 species are new records from the Majuli, and 30 and 29 species depict the global and regional biogeography interest; various interesting species are hypothesized to the biogeographic role of the ‘Assam gateway’.  High richness of Lecane > Lepadella ≥ Trichocerca, the richness of Testudinella and the paucity of Brachionus species are noteworthy features. The reports of 175 and 148 species from the floodplain lakes and small wetlands indicate biodiverse rotifer assemblages of wetlands of the two categories, and mark a useful contribution to Rotifera ecological diversity of the Indian and the tropical floodplains.