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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 6771

S.S.S. Sarma, Paulina Brena-Bustamante, and S. Nandini; Body size and population growth of Brachionus patulus (Rotifera) in relation to heavy metal (copper and mercury) concentrations. J.Environ.Sci.Health A. 43:547-553, 2008

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The effect of different sublethal concentrations of Cu2+ and Hg2+ was evaluated on the population growth and morphometry (body width and postero-lateral spines) of Brachionus patulus. When exposed to Cu2+ at lower concentrations (i.e., 2.5% and 5.0% of LC50), the population growth of B. patulus did not differ significantly from controls, while at the corresponding conditions, Hg2+ had adverse effects. The rate of population increase (r) varied from 0.13 to 0.28 per day, depending on the metal type and its concentration in the medium. In general, increase in metal concentration decreased the rate of population increase. When the daily growth rate was plotted as function of population density over the entire growth phase, a significantly inverse relation was obtained for controls and in treatments containing lower concentrations (2.5 and 5% of LC50) of heavy metals. However, under higher metal concentrations, the relation between population density and the daily growth rate became non-significant. Morphometric data showed that Cu caused larger bodied individuals, while the opposite effect was resulted due to Hg2+. Postero-lateral spines of B. patulus were also significantly influenced by the concentration of Cu2+ or Hg2+. Thus, compared to controls, there was reduction in the spine length, at low concentrations of Cu2+, but at all the four tested levels of Hg2+. Our data suggested that in addition to the population growth rate, morphometric measurements need to be considered for understanding the impact of heavy metals to brachionid rotifers.