Estudo do potencial de utilização do mexilhão dourado (Limnoperna fortunei) como bioindicador de genotoxicidade para avaliação da qualidade de ambientes aquáticos contaminados com mercúrio

Abstract

The Limnoperna fortunei (Golden mussel) is a bivalve freshwater mollusk, invasive and lacking natural predators, making it considered an environmental and economic problem. Bivalves such as the golden mussel can be considered as potential organisms to be used as bioindicators, because they are active filtering agents are immobile, have a wide geographic distribution and the capacity to accumulate high concentrations of contaminants, including heavy metals. Thatt is why, the present study presents like main contribution the evaluation of the potential of use of Limnoperna fortunei as bioindicator of genotoxicity to heavy metals, more specifically to HgCl2, in aquatic environments, evaluating the response of exposure to different concentrations of subacute and acute exposure to metal. Groups of 50 individuals exposed to water contaminated with HgCl2 at concentration of 0.001 mg/L, 0.005 mg/L, 0.01 mg/L, 0.02 mg/L and 0.1 mg/L (being the concentration of 0.01 mg/L considered limit to residual water according CONAMA) and were evaluated during 7, 15 and 30 days of exposure; or after injectable administration (AI) for acute assessment within 2 hours. The biological matrix used in the trials was the body massa of the mussel as a whole. The tests carried out were cell viability assays, in the order to evaluate the level of cytotoxicity and possibility of following the genotoxic test; alkaline comet test; Micronucleus test and necrotic cell number evaluation. Analyzes were done in triplicate and the data were treated by one-way ANOVA, complemented with Tukey’s multicomparison test, accepting as significant when p<0.05. Results demonstrated that the golden mussel offers some resistance to cytotoxic damage by subacute exposure; however, it has been shown to be sensitive to forced exposure (AI) at all concentrations tested. The comet test revealed than from the analysis of the 15th day, significant damage was observed in relation to the negative control at the highest concentration tested, however, on 30th da, three highest concentrations showed significant DNA damage. In the evaluation of the forced exposure, all the concentrations tested were able to induce significant damages to the mussel cells, being even superior to the observed damages to the positive control. Counting of cells with micronucleus revealed exposure of the golden mussel to tested concentrations of HgCl2 was not able to induce mutagenesis. Finally, necrotic cell counts showed that, in all concentrations tested for subacute exposure, necrotic process increased, especially in the group exposed to the highest concentration. For the acute exposure, although there is also an increase in the necrotic process, no differences were observed between the four higher concentrations tested. Taking the data together, it is possible to suggest that the golden mussel presents potential to be considered as possible genotoxicity bioindicator to evaluate the quality of aquatic environments, considering the metal used for the trials. However, complementary studies should be devloped to amplify and confirm the potential found in the present study, taking into account other toxicants known to be pollutants of water bodies.