Tolerance to zinc in populations of the earthworm Lumbricus rubellus from uncontaminated and metal-contaminated ecosystems

Zinc tolerance in Lumbricus rubellus populations from two metal-polluted (s melter and mine) sites was studied by comparing the effects of zinc with re sponses in a reference site strain. For the study, adult worms were collect ed directly from the field. Thus, no attempt was made to differentiate betw een tolerance resulting from population-level genetic adaptation or phenoty pic plasticity in metal physiology. To compare relative sensitivity for zin c, worms from the three populations were exposed in laboratory tests. Effec ts on survival, weight change, cocoon production, and internal zinc levels were measured. Prior to exposure, it was anticipated that worms from the me tal-contaminated sites would show substantially increased tolerance to zinc . This was not the case for all measured parameters. Thus, although differe nces in the shape of the dose-response relationships for survival and cocoo n production were found, substantial variations in measured responses, effe ct concentrations, or zinc accumulation rates were not apparent. Overall, t herefore, zinc tolerance is unlikely to be a major factor influencing the d istribution of L. rubellus in contaminated regions.