We evaluate diversity status of the Brachionidae of India and present an annotated checklist of 46 species excluding dubious and unconfirmed reports. These merit biodiversity value as ~27% of the global diversity of the taxon and ~81% of its Oriental species. We observed two Australasian elements, two Oriental endemics, one Indian endemic, one paleotropical and one cosmo (sub) tropical species. The cold-water Keratella serrulata and Notholca squamula are new records from eastern Himalayas. Maximum brachionid diversity (32 species) from Assam state of northeast India (NEI) is followed by the reports of 27 and 26 species from Tamil Nadu and West Bengal, respectively; 25 species each from Tripura and Maharashtra; and 24 species from Jammu & Kashmir. Brachionus, the most diverse brachionid genus, is widely distributed in India with low richness in hill states of NEI and coastal waters in particular. The Indian brachionid taxonomy is confounded with unconfirmed reports, misidentifications, invalid taxa, and inconsistent treatment of morphological variants, while analysis of cryptic diversity in Brachionus calyciflorus, B. caudatus, B. forficula, B. plicatilis, B. quadridentatus, B. urceolaris, Keratella cochlearis and K. quadrata species-groups awaits attention.

The diversity of Indian Brachionidae (Rotifera: Eurotatoria: Monogononta) and their distribution

Limnological survey of a small urban wetland of Meghalaya state of northeast India (NEI), undertaken at the littoral and semi-limnetic stations, reveals one of the biodiverse zooplankton assemblages (148 species belonging to 72 genera and 30 families) known from any lentic environ of the Indian sub-region. The speciose nature, peak constellation/sample of 83 zooplankton species, and diverse Rotifera (90 species) are hypothesized to environmental heterogeneity of this urban wetland in contrast to the general pattern of reduced richness expected in highly modified urban aquatic environments. The soft and de-mineralized waters are characterized by low zooplankton abundance. This study records high species diversity and evenness, and low dominance attributed to low and equitable abundance depicts ‘generalist’ nature of all species. Rotifera > Cladocera and Chydoridae > Lecanidae > Lepadellidae > Daphniidae are important at both stations, and Testudinellidae, Trichocercidae, and Macrothricidae are notable at the littoral station. Individual abiotic factors exert limited and differential spatial influence on various taxa, while the CCA registers a high cumulative influence of 10 abiotic factors on the littoral (87.37%) and semi-limnetic (75.81%) zooplankton assemblages. The spatial variations of composition, richness, similarities, abundance, diversity indices, and of the influence of individual abiotic factors are hypothesized to habitat heterogeneity amongst the sampled stations.

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Zooplankton Diversity of a Sub-Tropical Small Urban Wetland of Meghalaya, Northeast India with Remarks on Spatial Variations

The ecosystem services provided by freshwater zooplankton community (viz., rotifera, cladocera, copepoda and ostracoda) are very much significant and valuable. By feeding on phytoplankton or other members of zooplankton species, they act as primary consumers or secondary consumers, and hence playing a vital role in maintaining the biological configuration of the food web and overall balance of the aquatic ecosystem. Besides, the zooplankton play a central role in trophic cascade mechanisms; therefore, the eutrophic lakes of the world can be successfully restored by the so-called biomanipulation phenomena. Even in the diet of fish larvae, some highly unsaturated fatty acids (HUFA) and polyunsaturated fatty acids (PUFA) are provided by some zooplankters for their successful development; therefore, they act as a backbone for the successful aquaculture industry. An important role played by these valuable assets is to monitor the changes in the aquatic ecosystems due to climate change and various anthropogenic influences, like eutrophication, heavy metal load, changes in physicochemical parameters, etc. and that too in their early stages. Therefore the remedial steps can be trailed at very early stages to counteract the effects of these changes. Since the overall population dynamics of the zooplankton community is prone to disturbance induced by climate change, which is quite perturbing situation that the overall structure and function of the aquatic ecosystem may not get spoiled.

Zooplankton: The Significant Ecosystem Service Provider in Aquatic Environment

Hydrobiological survey of a ‘soft-water’ and ‘highly de-mineralized’ reservoir of Meghalaya state of northeast India is undertaken to analyze zooplankton diversity with reference to the spatio-temporal variations and influence of abiotic factors. The littoral and limnetic zooplankton assemblages of this subtropical reservoir without aquatic vegetation reveal total 36 species, and record lower abundance, quantitative dominance of Rotifera, sub-dominance of Cladocera and Copepoda and moderate species diversity. Keratella cochlearis, Bosmina longirostris, Polyarthra vulgaris, Mesocyclops leuckarti, Conochilus unicornis  and  Asplanchna priodonta  influence abundance, species diversity, dominance and equitability of zooplankton. We report differential spatial influence of individual abiotic factors with the relatively more importance at the limnetic region, and the canonical correspondence analysis registers 72.5% and 78.8% cumulative influence of 10 abiotic factors on the littoral and limnetic assemblages, respectively. The spatial differences of various diversity aspects and the influence of abiotic factors suggest habitat heterogeneity amongst the two regions. This study is a useful contribution to zooplankton diversity of the subtropical environs, and soft and de-mineralized waters in particular. Our results mark distinct contrast to the lowest richness and abundance of zooplankton noted from India vide  the preliminary 1990–91 survey of this reservoir.

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Zooplankton diversity of a soft-water and highly de-mineralized reservoir of Meghalaya (northeast India): the spatio-temporal variations and influence of abiotic factors

The body height becoming higher during metamorphosis can help flatfishes juveniles become more “flatten” after they turn 90-degree angle to settle down on the bottom. Such as in Japanese flounder and starry flounder, the increase of body depth during metamorphosis is the result of cell proliferation occurring along the dorsal and ventral rim of the body. And the change of body shape during metamorphosis is regulated directly by thyroid hormone. 

Molecular Basis of Body Depth Change during Metamorphosis

Zooplankters occupy an intermediate position in food web and are good indicators of the changes in water quality, because they are strongly affected by environmental conditions and respond quickly to changes in water quality. Hence, qualitative and quantitative studies of zooplankton are of great importance. The present study was undertaken to quantify the seasonal variations of zooplankton and selected physico-chemical variables (temperature, pH, Secchi disc transparency, dissolved oxygen, free CO2, bicarbonate, chloride, nitrate, phosphate and silicate concentrations) in the swamp of Purnia for one annual cycle (March 2007 to February 2008). The zooplankton taxa collected from the swamp water belong to three dominant groups viz. rotifers, cladocera and copepods. 26 zooplankton species were identified in which 17 belong to rotifer, 5 to cladocera and 4 to copepod. Rotifers were the most dominant group showing highest percentage (47.38%) composition and diversity followed by cladocera (39.64%) and copepod (12.98%). The zooplankton density in different seasons was in order of summer> winter > monsoon. The diversity of the overall zooplankton shows high in summer winter (H'= 0.964), summer (H'= 0.821) and less in monsoon (H'= 0.789). Density, diversity and composition of zooplankton also exhibited monthly variations. Brachionus, Keratella, Filiina, Cyclops and Diaptomus indicated organic pollution in the swamp. Zooplankters showed negative correlation with pH and DO2 in summer season as well as with free CO2, nitrate and phosphate during monsoon and winter. Further zooplankters exhibited negative correlation with water temperature and pH in monsoon and winter seasons respectively. The study established possible influences of the change in water quality to zooplankton population.

http://manuscript.sciknow.org/uploads/abr/pub/abr_1370502455.pdf

B. N. Pandey

Papers

Seasonal Variation in Zooplanktonic Community in Swamp of Purnia (Bihar), India