Competition of zinc, cadmium and calcium for binding sites in sperm of trout and carp

Heavy metal pollutions of aquatic ecosystems have already raised many concerns on aquatic organisms’health and survival especially on their sperm. The effects of a single metal on sperm may be totally different from cocktail of several metals because of their interactions, so the effects of zinc, cadmium and calcium on the trout and carp sperms and their competition have been examined by incubation of different concentrations of cold heavy metals with a radioactive competing metal. The results showed that radioactive 65Zn and 109Cd were not displaced from the trout sperm by calcium even at 3000 ppm concentration but radioactive cadmium was displaced equally well by cadmium or zinc, with a decrease in pellet activity to 38 and 37% of control values (0 ppm concentration) at 3000 ppm concentration, respectively in trout. Calcium was replaced by non-radioactive and radioactive zinc and cadmium as well as by calcium. The findings confirmed that at least part of heavy metals toxicity (especially cadmium) on fish sperm could be due to displacement of essential zinc and calcium. Both trout and carp sperms showed a similar pattern.