GENETIC ECOTOXICOLOGY .1. DNA INTEGRITY AND REPRODUCTION IN MOSQUITOFISH EXPOSED IN-SITU TO RADIONUCLIDES

Female mosquitofish (Gambusia affinis) were collected from two sites l ocated on the US Department of Energy's Oak Ridge Reservation that are contaminated with Cs-137, Sr-90, other radionuclides and chemical gen otoxicants. Fish from non-radionuclide contaminated environments locat ed off the reservation were also collected. DNA, extracted from liver tissue acid blood cells, was examined by gel electrophoresis for struc tural damage in the form of strand breakage. In general, the level of DNA strand breaks was elevated in fish from radionuclide-contaminated sites with observed differences in the number and type of strand break s between liver tissue and blood cells. The number of malformed embryo s was higher in fish at the contaminated sites, and varied with season . Fecundity was negatively correlated with the level of double strand breaks in the DNA of fish from one contaminated site. Females with bro ods that included malformed embryos had more DNA strand breakage than those that did not; and furthermore, a threshold effect was observed b etween the occurrence of malformed embryos and the presence of double strand breaks in the DNA of the mother. These findings have implicatio ns for both ecological risk assessment and evolutionary ecology.