CALCIUM FLUXES IN JUVENILE TILAPIA, OREOCHROMIS MOSSAMBICUS, EXPOSED TO SUBLETHAL WATERBORNE Cd, Cu OR MIXTURES OF THESE METALS

In juvenile tilapia the effects of waterborne Cu, Cd, and combinations of these metals on whole-body Ca fluxes were studied, using 45Ca as tracer. The maintenance of Ca homeostasis in fish is crucial throughout life but is especially important in young fish; Ca is also critical for growth. Single metal exposure had no effect on Ca fluxes after 6 d of exposure. In fish coexposed to 200 p.g Cu L“1 + 70 (jug Cd L -1 however, Ca influx was significantly decreased, whereas Ca efflux was not affected, As a result, the net flux was decreased. Because the effect on Ca fluxes observed in Cu/Cd-coexposed fish could not have been predicted from the effects of single metal exposures, this study underscores the impact of interactions between toxicants. Because natural freshwaters are commonly polluted by mixtures of metals, interactions between toxicants are important in risk assessment of heavy metals. Keywords—Cu/Cd interactions Ca fluxes Combination toxicology Fish Heavy metals