Variation in blood cell DNA in Carassius carassius from ponds near Chernobyl, Ukraine

Blood from approximately 400 crucian carp, Carassius carassius, from 12 ponds in the Ukraine, was analysed by flow cytometry to assess the possible relationships between chronic contaminant exposure and variation in the cellular DNA content. The ponds were located 20-30 km from Chernobyl in areas that received 3.7 x 10¹⁰-3.7 x 10¹¹ Bq ¹³⁷Cs km^-2 after the 1986 nuclear accident, as well as other radioactive and chemical contaminants. The fish populations consisted of both diploid and triploid individuals and the ploidy varied between ponds. Analysis of whole blood revealed aneuploid-like patterns in the DNA histograms of some fish, as well as hyperdiploid shoulders of the G₀/G₁ peak. The coefficient of variation (CV) of the G₀/G₁ peak has previously been employed to assess the variability in the DNA content of cells within individuals. The CV of individual fish varied between and within locations and very large CVs were found for some individuals. In some fish, DNA histograms showed a typical diploid or triploid cell population together with a smaller haploid population. Variations in the cellular DNA content similar to those reported here have been associated with exposure to radiation and other genotoxic agents in laboratory and field studies. However, the abnormalities we observed were not correlated with known contaminant distributions. While further work is needed, particularly in areas with substantially higher levels of radioactivity, these results suggest that the Chernobyl accident may have long-term genetic consequences for wild organisms inhabiting contaminated areas.