Chromium (Cr) accumulation in the freshwater crab, Zilchiopsis collastinensis

The freshwater crab, Zilchiopsis collastinensis was exposed in vivo to determine Cr accumulation in visceral content. After an acclimation period we added Cr(K2Cr2O7) at nominal concentrations of 2 mg l(-1) Cr(VI) and 5 mg l(-1) Cr(VI) and a control (T0) under the same conditions, without Cr. At days 1, 7 and 14, Cr was measured in water sediments and crabs and the bioconcentration factor (BCF) in relation to water and to sediment were obtained. Considering all samples and all the study period, crabs registered 3 times more Cr than sediments and 18 times more Cr than water. Cr levels in Z. collastinensis tissues were always lower in the control than in T1 and T2; no significant differences among days 1, 7 and 14 were found in the control. In the treatments, no significant increase in Cr levels in tissues were found between days 1 and 7, neither between days 7 and 14 in both concentrations tested. Significant differences were found between the control and T1 and T2 (p<0.001), but not between T1 and T2. The highest BCF obtained for Z. collastinensis were 51.82 and 51.42 in T1 and T2 in water at 14 days of exposure. This study shows the efficiency of freshwater crabs to accumulate Cr from water.