Biodiversity of Rotifera in some tropical floodplain lakes of the Brahmaputra river basin, Assam (NE India)

One hundred and sixteen species of Rotifera are recorded from seven floodpl ain lakes of the Brahmaputra basin (northeastern India), the highest rotife r biodiversity recorded from these biotopes in the Indian subcontinent to d ate. The Australasian Brachionus dichotomus reductus and Lecane batillifer; the Oriental Keratella edmondsoni, Lecane blachei and L. acanthinula; the Palaeotropical Lecane braumi, L. lateralis, L. unguitata, Trichocerca tropi s, Testudinella greeni and T. brevicaudata; the Pantropical Brachionus donn eri and a rather widely distributed Horaella brehmi represent taxa of bioge ographical interest. Three species are new additions to the Indian rotifer fauna and eight are new to the N.E. region. Lecanidae > Brachionidae = Colu rellidae > Trichocercidae > Testudinellidae comprise the largest fraction ( 68.0%) of the examined fauna. Comments are made on the general nature and c omposition of the rotifer taxocoenosis as well as on acidophilic elements, ecology of various taxa and on the species richness of different lakes.