Abstract
The influence of copper on osmoregulation in the freshwater amphipod Gammarus pulex was determined from the analysis of water permeability, haemolymph sodium concentration, sodium influx and gill Na +/K + ATPase and Mg 2+ ATPase activity. Exposure to nominal copper concentrations of 100 μg l −1 or greater caused a significant reduction in both haemolymph sodium concentration and sodium influx within 4 h. Measurements of water permeability, expressed as the half-time of exchange of body water ( t 1/2), excluded structural gill damage as the cause of this fall in haemolymph sodium. Copper at 10 μg l −1 or above in the assay solution significantly reduced gill Na +/K + ATPase activity. In contrast gill Mg 2+ ATPase activity was markedly less affected by copper. These differences in enzyme sensitivity were considered with respect to the potential mechanisms of copper toxicity.
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