Evaluation of bioconcentration and toxicity of five metals in the freshwater rotifer Euchlanis dilatata Ehrenberg, 1832.

Metals are widely used in modern society harming the environment; their toxicity cause environmental adverse effects to many organisms including zooplankton. This contribution employed: (a) acute and chronic toxicity tests, (b) epifluorescence image analysis, and (c) atomic absorption techniques, to analyze toxicity of four trace (copper, iron, nickel, and zinc), and one non-trace metals (mercury) on the freshwater rotifer Euchlanis dilatata. This work integrated results of Bioconcentration Factors (BCF's), sites of entry and accumulation and to determine mechanisms of uptake and toxicity of these five metals of the freshwater rotifer Euchlanis dilatata. This integral analysis enhanced our understanding of knowledge on: (a) the toxicity mechanisms, (b) sites of metal entry and concentration inside the rotifer, (c) bioconcentration and body burdens. As expected, Hg the non-trace metal used here, was the most toxic. Our results suggest that the toxicity is ameliorated in the rotifer by selecting feeding avoiding the most toxic particles and reducing adverse effects on reproduction, until mortality per se reduces reproduction. The chronic effect on ingestion rate was quite sensitive for all metals whereas reproduction was slightly affected. The combination of acute and chronic tests and determination of BCF's for each metal allowed calculation of the acute and chronic body burdens. Body burdens again confirmed that mercury was the most toxic metal of the five employed here.