Search

We examined effects of radionuclide exposure at two atomic blast sites on kangaroo rats ( Dipodomys merriami) at the Nevada Test Site, Nevada, USA, using genotoxicity and population genetic analyses. We assessed chromosome damage by micro- nucleus and flow cytometric assays and genetic variation by randomly amplified polymorphic DNA (RAPD) and mitochondrial DNA (mtDNA) analyses. The RAPD analysis showed no population structure, but mtDNA exhibited differentiation among and within populations. Genotoxicity effects were not observed when all individuals were analyzed. However, individuals with mtDNA haplotypes unique to the contaminated sites had greater chromosomal damage than contaminated-site individuals with haplotypes shared with reference sites. When interpopulation comparisons used individuals with unique haplotypes, one contaminated site had greater levels of chromosome damage than one or both of the reference sites. We hypothesize that shared-haplotype individuals are potential migrants and that unique-haplotype individuals are potential long-term residents. A parsimony approach was used to estimate the minimum number of migration events necessary to explain the haplotype distributions on a phylogenetic tree. The observed predominance of migration events into the contaminated sites supported our migration hypothesis. We conclude the atomic blast sites are ecological sinks and that immigration masks the genotoxic effects of radiation on the resident populations. Keywords—Population genetics Dipodomys merriami Chromosomal damage Nuclear weapons Nevada Test Site

†Department of Wildlife and Fisheries Sciences, Texas AM Accepted 6 February 1998)Abstract—The effects of radionuclide contamination on genetic structure of eastern mosquitofish (Gambusia holbrooki)populationsfrom the U.S. Department of Energy’s Savannah River Site (SRS) were investigated to develop methods of assessing ecologicalrisk of chronic exposures to xenobiotics. Fish from two contaminated and two reference sites were examined by the randomlyamplified polymorphic DNA (RAPD) technique, which revealed that the frequency of three markers was greater in the contaminatedthan the reference sites and that the frequency of two markers was greater in the reference than in the contaminated sites. A previousstudy examined populations of western mosquitofish (G. affinis) from the Oak Ridge National Laboratory (ORNL) and found thatcertain RAPD markers were present in radionuclide-contaminated ORNL populations at a higher frequency than in referencepopulations. The ‘‘contaminant-indicative’’ markers observed in the SRS populations were the same size and amplified by the samepolymerase chain reaction primers used in the ORNL study. Southern blot analysis revealed that the SRSG. holbrooki contaminant-indicative markers were homologous to the ORNL G. affiniscontaminant-indicative markers. The observation that two speciesshow similar patterns of band frequency shifts at two separate localities is consistent with the hypothesis that these DNA markersmay originate from genetic elements that provide a selective advantage in contaminated habitats. Thus, the methodology used inthese studies may prove to be useful to indicate population-level effects of environmental contamination.Keywords—Population genetics Gambusia Radiation Evolutionary toxicology Randomly amplified polymorphicDNAINTRODUCTION

In 1993, great blue heron (Ardea herodias; GBH) eggs were collected from 10 colonies on the upper Mississippi River (UMR). They were then artificially incubated until pipping and analyzed for mercury, selenium, and organochlorines. Livers of embryos were analyzed for hepatic microsomal ethoxyresorufin-O-dealkylase (EROD) activity and four measures of oxidative stress. Brains were measured for asymmetry and blood was measured for the coefficient of variation of DNA (DNA CV). Organochlorine concentrations were generally low (geometric mean DDE = 1.3 μg/g wet weight; polychlorinated biphenyl [PCB] = 3.0 μg/g; 2,3,7,8-tetrachlorodibenzo-p-dioxin [TCDD] = 11.5 pg/g). Eggshell thickness was negatively correlated with DDE concentrations. Mercury (geometric mean = 0.8 μg/g dry weight) and selenium (3.1 μg/g dry weight) concentrations in GBH eggs were within background levels. EROD activity was not correlated with total PCBs, TCDD, or toxic equivalents (TEQs), based on the relative contribution of individual PCB congeners, dibenzodioxins (PCDDs), and dibenzofurans (PCDFs) to total calculated TEQs. Three of the four measures of oxidative stress were correlated with mercury concentrations. Twenty of 43 (47%) embryo brains were asymmetrical and the embryos with asymmetrical brains had higher EROD concentrations in the liver and higher DNA CV in the blood than embryos with symmetrical brains.

The explosion of the Chernobyl Nuclear Power Plant resulted in some of the most radioactively contaminated habitats on earth. Despite evacuation of all human inhabitants from the most contaminated areas, animals and plants continue to thrive in these areas. This study examines the levels of contamination and genetic damage associated with radiocesium in catfish (Ictalurus punctatus) from the cooling pond and a control site. In general, catfish from the cooling pond exhibit greater genetic damage, and the amount of damage is related to the concentration of radiocesium in individual fish. Genetic damage is primarily in the form of DNA strand breaks, with few micronuclei being observed in contaminated fish. The possible roles that acclimation and adaption play in the response to high levels of radiation exposure are discussed.

More than 8.2 billion ha of cropland, gardens, and forests are treated with the herbicide glyphosate each year. Whereas the toxicity of glyphosate and associated adjuvants has been measured in other vertebrates, few, if any, studies have looked at their effects in reptiles. In some instances, management of turtle habitat requires control of successional stages through application of herbicides. Adults and juvenile turtles may be exposed directly, whereas embryos may contact the chemicals through the soil. In the present study, we exposed eggs of red-eared sliders (Trachemys scripta elegans) to single applications of herbicide ranging from 0 to 11,206 ppm wet weight of glyphosate in Glypro® and 0 to 678 ppm of the surfactant, LI700. Hatching success at the highest concentration was significantly lower (73%) than in other treatments (80–100%). At hatch, turtles at the highest concentration weighed less than those at other concentrations. During a 14-d holding period, we observed dose–response relationships in the ability of hatchlings to right themselves when turned on their backs. At the end of the holding period, hatchlings at the highest dose level were still lighter, and somatic indices were lower, than those in other treatments. Genetic damage, as measured by flow cytometry, increased with treatment concentration except for the highest dose. We conclude that because of the high concentrations needed to produce effects and the protection offered by several centimeters of soil or sediment, glyphosate with LI700 poses low levels of risk to red-eared slider embryos under normal field operations with regards to the endpoints measured in the present study. Carelessness in handling glyphosate or failure to follow label directions may produce adverse effects. There also is a risk that the health of turtle embryos may be affected in ways not measured in the present study.

The wetlands of Sumgayit in the Azerbaijan Republic contain complex mixtures of contaminants, including polycyclic aromatic hydrocarbons (PAHs), mercury, organochlorine pesticides, and polychlorinated biphenyls. Marsh frogs (Rana ridibunda) were collected from several contaminated wetlands within the city as well as from two reference sites outside the city. Sediment samples revealed heterogeneous patterns of PAH and mercury concentrations throughout Sumgayit, with the highest levels occurring east of the Sumgayit River, within the industrial zone. Flow cytometry and micronucleus assay revealed elevated estimates of genetic damage in frogs from the wetlands east of the Sumgayit River compared to frogs from the reference sites. Flow cytometric data showed a significant correlation with sediment mercury concentrations, whereas population micronucleus frequencies were significantly correlated with high-molecular-weight PAHs.

Four species of reptiles (diamondback water snake [Nerodia rhombifer], blotched water snake [N. erythrogaster], cottonmouth [Agkistrodon piscivorus], and red-eared slider [Trachemys scripta]) were collected at two contaminated and three reference sites in Texas, USA. Old River Slough has received intensive applications of agricultural chemicals since the 1950s. Municipal Lake received industrial arsenic wastes continuously from 1940 to 1993. Blood samples were analyzed for organochlorines, potentially toxic elements, genetic damage, and plasma cholinesterase (ChE). Dichlorodiphenyldichloroethylene (DDE) concentrations reached as high as 3.0 ppm (wet weight) in whole blood of a diamondback water snake at Old River Slough, a level probably roughly equivalent to the maximum concentration found in plasma of peregrine falcons (Falco peregrinus) in 1978 to 1979 when DDE peaked in this sensitive species. Possible impacts on diamondback water snakes are unknown, but at least one diamondback water snake was gravid when captured, indicating active reproduction. Arsenic was not found in red-eared sliders (only species sampled) from Municipal Lake. Red-eared sliders of both sexes at Old River Slough showed declining levels of ChE with increasing mass, suggesting a life-long decrease of ChE levels. Possible negative population consequences are unknown, but no evidence was found in body condition (mass relative to carapace length) that red-eared sliders at either contaminated site were harmed.