Relation between mercury, monomethylmercury and selenium in the muscle of coastal Brazilian fishes

摘要

The study assesses the accumulation of selenium and mercury, as methylmercury, in the muscle tissues of a carnivorous (N=34), and a planktivorous (N=27) fish species. Absolute concentrations of T-Hg (fresh weight basis) in muscle were higher in the carnivorous fish (median 0.15 mu g g~(-1)) than in the planktivorous fishes (median 0.02 mu g g~(-1)). Significant positive linear relationship was observed between T-Hg and T-Se molar concentrations in fish muscle (R=0.67; p=0.00). Highly significant positive linear relationship was observed between MeHg and T-Se molar concentrations in fish muscle (R=0.96; p=0.00). The median molar concentrations of T-Se in muscle of carnivorous fish were approximately eight times those of T-Hg in the same tissue, while this same ratio was 20 for planktivorous fish. Carnivorous fish which presented the highest percentage MeHg in the muscle (98 percent), showed a strong significant positive linear correlation between the sum of T-Hg and T-Se molar concentrations and the total length of the specimens (R=0.86; p=0.00), whereas the planktivorous fish that presented the lowest percentage MeHg (52 percent) showed a high correlation coefficient (R=0.76; p=4 X 10~(-6) with the total length. Following our results, we could hypothesis that the fish muscle has a finite number of receptor sites for selenium, which increase with the age, also length. Furthermore, the molar excess of selenium suggests that methylmercury may be directly associated (at biomolecular level) with selenium compounds.