Increased cytotoxic and genotoxic tolerance of Eisenia fetida (Oligochaeta) to cadmium after long-term exposure.
ABSTRACT Since life-cycle studies showed that the earthworm species Eisenia fetida can develop increased tolerance after long-term exposure to a sub-lethal concentration of Cd in the laboratory, we assessed both the cytotoxicity and genotoxicity of Cd in a long-term Cd-exposed population. We exposed E. fetida specimens from this population, from a laboratory control population and from a field population to various concentrations of CdSO(4) in artificial soil water. Toxic effects were measured using the MTT test and the comet assay. The group that had been exposed to Cd for more than a decade was found to be more tolerant to the deleterious effects of Cd at both cellular and molecular levels than the laboratory control population. The field population, which came from a severely metal polluted environment, displayed high tolerance at molecular level as well. The results provide novel biomarker evidence of increased Cd tolerance in E. fetida, but the mechanisms supporting the apparent tolerance, still need to be clarified.
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ABSTRACT: The choice of a suitable species to translate pollution signals into a quantitative monitor is a fundamental step in bio-monitoring plans. Here we present the results of three years of biomonitoring at a new coal power plant in central Italy using three different aquatic and terrestrial wildlife species in order to compare their reliability as sentinel organisms for genotoxicity. The comet assay was applied to the common land snail Helix spp., the lagoon fish Aphanius fasciatus, and the green frog Rana esculenta sampled in the area potentially exposed to the impact of the power station. The tissue concentration of some expected pollutants (As, Cd, Ni, Pb, Cr) was analysed in parallel samples collected in the same sampling sites. The three species showed different values in the comet assay (Tail Intensity) and different accumulation profiles of heavy metals. Aphanius fasciatus showed an increasing genotoxic effect over time that paralleled the temporal increase of the heavy metals, especially arsenic, and the highest correlation between heavy metals and DNA damage. Helix spp. showed levels of damage inversely related to the dis-tance from the source of pollution and in partial accordance with the total accumulation of trace elements. On the contrary, Rana esculenta showed a low capability to accumulate metals and had inconsistent results in the comet test. The fish appeared to be the most efficient and sensitive species in detecting chemical pollution. Overall, both the fish and the snail reflected a trend of in-creasing pollution in the area surrounding the power plant across time and space [Current Zoology 60 (2): 308–321, 2014]. Wildlife sentinels are regarded as those populations that can react to environmental contaminants before they impact human health and ecosystems without sig-nificant adverse effects (Stahl, 1997; Van der Schalie et al., 1999; Rabinowitz et al., 2005; Carere et al., 2010). A crucial issue is the selection of the species to monitor. This can be achieved by adopting a number of criteria: (i) a simple relationship between the source and tissue concentrations of the pollutant(s); (ii) its consistency across sampling sites and years; (iii) relative insensitivi-ty to the pollutant(s); (iv) being abundant and easy to sample and to age; (v) a good knowledge about its ecology and physiology; (vi) being sedentary or having a limited home range (Martin and Coughrey, 1982; Philips and Segar, 1986; Philips and Rainbow, 1993; Beeby, 2001). Many physical and chemicals contaminants can cause structural and functional changes in the molecular com-pounds of living cells. DNA is an important target of environmental stress due to persistent organic pollutants in both aquatic and terrestrial organisms (Frenzilli et al., 2001). The contaminants can create DNA lesions, inclu-ding strand-breaks, modified bases, DNA-DNA and DNA-protein crosslinks (Eastman et al., 1992). DNA strand-breaks (Shugart, 1990; Balpaeme et al., 1996) are a common modification that may be induced by a wide range of agents and mechanisms (Nacci and Nelson, 1992; Mitchelmore et al., 1998). Therefore, DNA dama-ge has been proposed as a biomarker for assessing the genotoxic properties of environmental contaminants in biomonitoring studies (Everaats et al., 1998; Felder et al., 1998; Theodorakis and Shugart, 1998; Xu et al., 1999). Among the various techniques used to assess the genotoxicity of environmental pollutants, the single cell gel electrophoresis (SCGE), or comet assay, has advan-tages that make it ideal for use in sentinel organisms (Mitchelmore and Chipman, 1998; Rojas et al., 1999). This technique can detect early signs of exposure to genotoxicants and show primary DNA damage as single or double strand breaks, alkali-labile sites and cross-links in eukaryotic cells (in vivo and in vitro) in differ-ent tissues (Singh et al., 1988; Tice et al., 2000; Reinecke and Reinecke, 2004; Bonisoli-Alquati et al., 2010; Mosesso et al., 2012; Dallas et al., 2013). Many studies used the comet assay to determine DNA
Current Zoology 02/2014; 60(2):308-321. · 1.81 Impact Factor
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ABSTRACT: Low doses of ionizing radiation and chemical toxic agent effects on biological systems on different organization levels have been studied by numerous researchers. But there is a clear lack of experimental data that allow one to reveal molecular and cellular adaptations of plants and animals from natural populations to adverse effects of environmental factors. The present study was aimed to assess genotoxic effects in earthworms Aporrectodea caliginosa Savigny and Lumbricus rubellus Hoffmeister sampled from the populations that during numerous generations inhabited the territories with a technogeneously enhanced content of natural origin radionuclides and heavy metals in soil. The levels of the DNA damage detected with alkaline and neutral versions of Comet!assay in invertebrates from contaminated territories were established not to differ from the spontaneous level found in the animals from the reference population. At the same time the rate of the DNA damage reparation induced in A. caliginosa sampled from the contaminated sites with additional acute γ!irradiation (4 Gy) was found to be considerably higher as compared with earthworms from the reference population.Radiatsionnaia biologiia, radioecologiia / Rossiĭskaia akademiia nauk 01/2015; 55(1):24-34. DOI:10.7868/S0869803115010051