Comparison of two freshwater turtle species as monitors of radionuclide and chemical contamination: DNA Damage and residue analysis

Abstract

Two species of turtles that occupy different ecological niches were compared for their usefulness as monitors of freshwater ecosystems where both low-level radioactive and nonradioactive contaminants are present. The pond slider (Truchemys scri tu) and common snapping turtle (Chelydra serpentinu) were analyzed for the presence of 90Sr, ' 7Cs, 60Co, and Hg, radionuclides and chemicals known to be present at the contaminated site, and single-strand breaks in liver DNA. The integrity of the DNA was examined by the alkaline unwinding assay, a technique that detects strand breaks as a biological marker of possible exposure to genotoxic agents. This measure of DNA damage was significantly increased in both species of turtles at the contaminated site compared with turtles of the same species at a reference site, and shows that contaminant-exposed populations were under more severe genotoxic stress than those at the reference site. The level of strand breaks observed at the contaminated site was high and in the range reported for other aquatic species exposed to deleterious concentrations of genotoxic agents such as chemicals and ionizing radiation. Statistically significantly higher concentrations of radionuclides and Hg were detected in the turtles from the contaminated area. Mercury concentrations were significantly higher in the more carnivorous snapping turtle compared with the slider; however, both species were effective monitors of the P contaminants.

DNA damage and radiocesium in channel catfish from chernobyl

“…Radiation and other carcinogens are known to cause genetic damage [5][6][7][8][9][10][11][12][13]. However, few studies have investigated DNA damage in relation to radionuclides in natural settings [14][15][16][17][18]. However, studies that examine genetic damage in natural populations provide useful information about the potential biological hazards associated with such toxic agents and the amelioration or exacerbation of effects via ecological pathways.…”

“…The alkaline unwinding technique is a rapid method of assessing strand breaks. Recent studies have shown that the number of breaks, as determined from this method, can be associated with various toxic agents [11][12][13][14][15]26].…”

DNA strand breakage in freshwater mussels (Anodonta grandis) exposed to lead in the laboratory and field

“…These assays are being developed and used in fish [16][17][18], but few assays have been adapted for alternate aquatic species. Most of these assays use either alkaline elution techniques [19] or alkaline unwinding followed by fluorometric detection [20]. These techniques have the advantage of being rapid, relatively inexpensive, and requiring little specialized instrumentation other than a spectrofluorometer.…”

“…Neither of these assays, however, directly quantifies DNA strand lengths, in particular the strand lengths of double-stranded DNA. Data from alkaline elution and/or unwinding techniques are expressed as an F-value, which represents either the fraction of double-stranded DNA present following alkaline unwinding [16,20] or a strand-scission factor calculated from alkaline elution kinetics [19].…”

Application of a fish DNA damage assay as a biological toxicity screening tool for metal plating wastewater

“…Among the many assays that have been developed for the assessment of DNA damage, alkaline unwinding and agarose gel electrophoresis are reported to be efficient and rapid methods for evaluating various toxic agents [5,16]. Researchers have demonstrated the association between various toxic agents, including heavy metals and radionuclides, and DNA in natural populations using alkaline unwinding techniques [5,17]. This procedure has proven to be useful for assessing the number of DNA strand breaks.…”