Diversity of rotifers (Rotifera, Eurotatoria) of Loktak lake, Manipur, North-eastern India

摘要

The rotifer communities of Loktak lake (a Ramsar site), Manipur, N.E. India, contain 120 species belonging to 36 genera and 19 families and represent the richest biodiversity of Phylum Rotifera known from any aquatic ecosystem of the Indian subcontinent. Biogeographically interesting elements include one Australasian, three Oriental and seven Palaeotropical species. Cosmopolitan species (69.2%) show higher richness while Cosmotropical > Pantropical species are well represented. The rotifer fauna is characterized by notable richness of Lecanidae > Lepadellidae > Trichocercidae > Brachionidae, general 'tropical character', occurrence of several acidophilic species, and a paucity of Brachionus spp. The richness (47-79; mean +/- SD 57 +/- 10 species) follows multimodal pattern of monthly variations with a peak during winter. The rotifer communities have 52.3-80.6% temporal similarity, and show lack of seasonal periodicity of occurrence of different families. The Rotifera form an important quantitative component of zooplankton (45.8 +/- 8.1%), and have higher species diversity, lower dominance and higher evenness. Richness and density are inversely correlated with water, temperature, rainfall, hardness, nitrate, chloride and total dissolved solids and positively correlated with dissolved oxygen. In addition, richness is inversely correlated with pH.