HEAVY-METAL EFFECTS ON THE METABOLIC-ACTIVITY OF ELLIPTIO-COMPLANATA - A CALORIMETRIC METHOD

The effects of short time exposure to mercury (Hg2+), cadmium (Cd2+), and copper (Cu2+) ions on the metabolic activity of gill tissue from t he freshwater bivalve Elliptio complanata were investigated by isother mal calorimetry and respirometry. Metabolic heat rates were altered fo llowing exposure of gill tissue to these ions over the concentration r ange from 10(-6) to 10(-3) M, The effects of metal ions on metabolic h eat rates were metal ion specific and time and concentration dependent . Treatment of tissue with low concentrations of Hg2+ and Cu2+ for sho rt times caused stimulation of metabolic heat rates. Longer exposures and higher concentrations caused inhibition, Cadmium was inhibitory un der all conditions tested, Treatment of mitochondria isolated from gil l and muscle tissues showed a similar pattern of stimulation of respir atory rate at low concentration and inhibition at higher concentration , Analysis of CO2, and O-2 from the headspaee gasses in the calorimete r ampule showed an enhancement of respiratory quotient (RQ, i.e., R(CO 2)/R(O2) where R = rate) following addition of 10(-3) M Cd2+ for 30 mi n. The microcalorimetric method proved to be a useful technique to ass ess toxicity of heavy metals on the Kills of a freshwater bivalve.