Methylmercury chloride and selenomethionine interactions on health and reproduction in mallards

Abstract

Abstract-Adult mallards (Anas platyrhynchos) were fed a control diet or diets containing 10 ppm mercury as methylmercury chloride, 10 ppm selenium as seleno-DL-methionine, or 10 ppm mercury plus 10 ppm selenium. One of 12 adult males fed 10 ppm mercury died, and eight others suffered paralysis of the legs by the time the study was terminated. However, when the diet contained 10 ppm selenium in addition to the 10 ppm mercury, none of 12 males became sick. In contrast to the protective effect of selenium against mercury poisoning in males, selenium plus mercury was worse than selenium or mercury alone for some measurements of reproductive success. Both selenium and mercury lowered duckling production through reductions in hatching success and survival of ducklings, but the combination of mercury plus selenium was worse than either mercury or selenium alone. Controls produced an average of 7.6 young per female, females fed 10 ppm selenium produced an average of 2.8 young, females fed 10 ppm mercury produced 1.1 young, and females fed both mercury and selenium produced 0.2 young. Teratogenic effects also were worse for the combined mercury plus selenium treatment; deformities were recorded in 6.1% of the embryos of controls, 16.4% for those fed methylmercury chloride, 36.2% for those fed selenomethionine, and 73.4% for those fed methylmercury chloride and selenomethionine. The presence of methylmercury in the diet greatly enhanced the storage of selenium in tissues. The livers of males fed 10 ppm selenium contained a mean of 9.6 ppm selenium, whereas the livers of males fed 10 ppm selenium plus 10 ppm mercury contained a mean of 114 ppm selenium. However, selenium did not enhance the storage of mercury. The results show that mercury and selenium may be antagonistic to each other for adults and synergistic to young, even within the same experiment.

Histologic, Neurologic, and Immunologic Effects of Methylmercury in Captive Great Egrets

“…Ataxia, progressing to paralysis has been described in non-fish-eating birds dosed with methylmercury (Borg et al, 1970;Fimreite and Karstad, 1971;Pass et al, 1975;Heinz and Hoffman, 1998). Surprisingly, postural, ambulatory, and motivational deficits appeared to precede loss of foraging skills in low-dosed birds (Bouton et al, 1999).…”

“…Negative effects on the neurological (Chang, 1977;Burbacher et al, 1990;Nagashima, 1997) and immune systems (Ilback, 1991;Ilback et al, 1996) and other tissues (SnelgroveHobson et al, 1988) are well documented in humans and captive mammals. Effects of methylmercury exposure have been reported in captive birds (Borg et al, 1970;Fimreite and Karstad, 1971;Soares et al, 1973;Pass et al, 1975;Hughes et al, 1976;Heinz and Hoffman, 1998;Hoffman and Heinz, 1998), including trans-generational effects (Heinz, 1975(Heinz, , 1976(Heinz, , 1979. These studies have focused on non-piscivorous species, whereas the top predators in aquatic systems are often piscivorous mammals and birds.…”

Status of selenium in south San Francisco Bay—A basis for modeling potential guidelines to meet National tissue criteria for fish and a proposed wildlife criterion for birds

“…4 and additional details in the Sources of Selenium section) (California Regional Water Quality Control Board, 2008). Complex Hg and Se interactions are documented in birds and fish both in the laboratory and in some (but not all) locations in the field (Heinz and Hoffman, 1998;Penglase and others, 2014). Antagonistic (that is, mitigating) effects on bioaccumulation, linked bioaccumulation, and synergistic effects on reproduction are examples of ways that Hg and Se can interact where exposures are constant or controlled.…”

Pesticide Use in South Africa: One of the Largest Importers of Pesticides in Africa

“…At even higher levels, convulsions occur, which lead to death. Apart from its direct toxic effects, MeHg might have adverse interactive potentiation with other pollutants such as polychlorinated biphenyls, -dibenzo-p-dioxins, -dibenzofurans, p,p'-DDE, metals and selenium in specifically the aquatic environment specifically (Walker & Livingstone, 1992;Heinz & Hoffman, 1998). OPs prevent the formation of the enzyme cholinesterase (ChE), which ensures that the chemical signal that causes a nerve impulse is stopped at the appropriate time and because of this, is neurotoxic to vertebrates and non-target invertebrates.…”