Pre-exposure to cadmium or zinc alters the heart rate response of the crayfish Procambarus clarkii towards copper

Exposure to sub-lethal concentrations of a pollutant induces, in some organisms, an acclimation process which increases their resistance to other substances (cross-acclimation). Understanding this phenomenon is important as a basis for a better comprehension of the effects of pollutants in ecosystems. In this paper we investigated whether the exposure to Cd or Zn is able to modify the heart rate response of the crayfish Procambarus clarkii to acute Cu stress. A first set of experiments provided the basis to understand heart rate changes induced by varying Cd or Zn concentrations. In a second set of experiments crayfish were acclimated for 96 h to control water, Cd or Zn enriched water, and then exposed to a 10 mg L-1 Cu solution, known to induce bradycardia in this species. Bradycardia was suppressed in specimens previously exposed to Cd or Zn but not in those exposed to clean water, providing a clear evidence of a cross-acclimation in the heart rate response of P. clarkii.