The effect of copper on osmoregulation in the freshwater arnphipod Gammarus pulex

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 Mg2+ ATPase activity. Exposure to nominal copper concentrations of 100 mug 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 mug l(-1) or above in the assay solution significantly reduced gill Na+/K+ ATPase activity. In contrast gill Mg2+ ATPase activity was markedly less affected by copper. These differences in enzyme sensitivity were considered with respect to the potential mechanisms of copper toxicity. (C) 2003 Elsevier Science Inc. All rights reserved.