Interesting rotifers (Rotifera: Eurotatoria) from floodplain lakes of lower Brahmaputra river basin of Assam, northeast India

Abstract

Abstract. The plankton and semi-plankton samples collected from four floodplain lakes (beels) of Barpeta district of lower Brahmaputra river basin, Assam state, northeastern India (NEI) revealed eighteen rotifer species of biodiversity and biogeographic interest belonging to five families and six genera. One species is new to the Indian Rotifera and one species is new to Assam. Our collections are characterized by two Australasian elements, five Oriental endemics, seven paleotropical species, and one cosmo (sub) tropical species. Nine species, restricted to date to NEI, are examples of regional distribution importance in India while six species depicted disjunct distribution in the country. Interestingly, seven species are categorized as Eastern hemisphere elements. All the taxa are illustrated to warrant validation as an increasing magnitude of 'unverifiable records' is a serious impediment for the progress of rotifer biodiversity in India.

Northeast India: An important region with a rich biodiversity of Rotifera

“…Interestingly, the richness in these Ramsar sites is higher than the following records: 111 species from the floodplains of Argentina ; 124 species (Oguta lake) and 136 species (Iyi‐Efi lake) in the Niger delta ; 130 species from Lake Guarana, Brazil ; 106 taxa from Thale‐Noi Lake, a Ramsar site in Thailand ; 104 species from Laguana Bufeos, Bolivia and 114 taxa examined from the Rio Pilcomayo National park (a Ramsar site), Formosa, Argentina . On the other hand, our values of S for certain individual beels and pats of NEI, that is, 75 species from Utra and Waithou pats of Manipur ; 85 species from Ghorajan beel of lower Assam; 69–93 species from different beels of Assam and 62–73 species from 15 pats of Manipur are somewhat lower than ATBI reported by Dumont and Segers due to lack intensive surveys of these sites. However, we caution against over emphasis on comparisons with poor richness reported from the floodplains of Kashmir , Bihar , Assam and West Bengal because of incomplete species inventories, inadequate samplings or over‐looking identification of small taxa.…”

“…The distinct richness of the littoral‐periphytonic elements and paucity of euplanktonic species in the beels and pats of northeast India suggests a lack of definitive pelagic habitats . It is worth noting that a large number of small‐sized species concomitant with low population densities characterize our collections.…”

“…Our comments on ecology were based on qualitative and quantitative plankton samples collected from the different sampling sites monthly and seasonally from 30+ beels of the Brahmaputra river basin of Assam and 15 pats of Manipur state. The former were collected by towing plankton net (#50 µm) and the latter were collected monthly/seasonally by filtering 25 l water each through plankton net (#50 µm) and were preserved in 5% formalin.…”

Rotifer communities of religious water bodies of Haryana (India): Biodiversity, distribution and ecology

“…2 Devi (1997) observed maxima of rotifers during pre-monsoon and monsoon period. The present findings are in contrast to the annual pattern with winter maxima observed in Deepor Bell (Sharma, 2010) and Loktak Pat (Sharma, 2009), whereas Sharma (1992Sharma ( , 2009Sharma ( , 2010 and Sharma and Sharma (2012) observed lack of any definite pattern of quantitative variation of the rotifers supporting the present results. The values of different physico-chemical characteristics are depicted in Table 2.…”

“…Overall mean value of species dominance was recorded highest (0.42) at the site Pehowa and least (0.1) was observed at Pindara. A range from 0.049 to 0.110 was observed by Sharma and Sharma (2012) at the floodplain lake of Brahmputra river basin India. The value of species evenness (Table 3) indices near 1 or equal to 1 shows an even distribution of species throughout the year whereas the values far from 1 show the uneven distribution of species.…”