Evaluation of the toxic effect of cadmium chloride and copper sulphate on the rotifer Brachionus plicatilis was carried out. The calculated 24 hrs LC50 concentration values were 0.66 and 0.55 mgl for cadmium and copper, respectively. The exposure of B. plicatilis to sublethal concentrations of cadmium and copper at 25ºC and under an algal density of 10x106 cellsml of Nannochloropsis salina showed significantly decrease of population growth (r). Copper sulphate showed significantly decrease of the daily growth rate when compared with daily growth rate of control, while after 6 days of exposure to cadmium chloride, the population growth did not differ significantly from control. Scanning electron micrographs of exposed B. plicatilis to sublethal concentrations of cadmium and copper showed remarkable morphological changes on the corona, integument and foot while the rank order of increasing morphological damage was cadmium
Key words: Brachionus plicatilis, heavy metals, population density, scanning electron micrographs
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