Biomarkers for Ex Situ Ni and Pb Exposure in Common Carp (Cyprinus carpio L.)

This work aimed to study the effects of heavy metal exposure on the respiration rate and histological structure of common carp (Cyprinus carpio L.) gills. Fish were treated with different soluble concentrations of Ni and Pb in laboratory conditions for a total acute period of 72 hours. The metal concentrations were prepared as 75, 50 and 25% of the maximum permissible levels (100%) set by law. The results showed a higher index of respiration rate in the fish from all experimental tanks for both metals, compared to the control in the beginning of the experiment, but there was no pattern of increase or decrease in relation to the metal concentrations. After 72 hours of exposure we observed the same pattern, but in addition the respiration rate of the fish in the tanks treated with Pb showed an increase in a dose-dependent manner. We also observed different histological changes in the gill epithelium, which included proliferative and degenerative changes, as well as changes in the circulatory system. In addition, the degenerative changes were more pronounced in the fish, treated with Pb concentrations, and the blood circulatory system showed mainly vasodilatation, which caused pathological changes in the gills. In sum, we can conclude that Ni and Pb have severe effects on the respiration rate and gill histology of common carp, even at concentrations, which were lower than the allowable ones.