Reproduction in mallards exposed to dietary concentrations of methylmercury |
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Authors: | Gary H Heinz David J Hoffman Jon D Klimstra Katherine R Stebbins |
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Institution: | (1) U.S. Geological Survey, Patuxent Wildlife Research Center, BARC-East, Building 308, 10300 Baltimore Avenue, Beltsville, MD 20705, USA |
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Abstract: | The purpose of this experiment was to use mallards (Anas platyrhynchos) tested under controlled conditions to determine how much harm to reproduction resulted from various concentrations of mercury
in eggs. Breeding pairs of mallards were fed a control diet or diets containing 1, 2, 4, or 8 μg/g mercury, as methylmercury
chloride. Mean concentrations of mercury in eggs laid by parents fed 0, 1, 2, 4, or 8 μg/g mercury were 0.0, 1.6, 3.7, 5.9,
and 14 μg/g mercury on a wet-weight basis. There were no signs of mercury poisoning in the adults, and fertility and hatching
success of eggs were not affected by mercury. Survival of ducklings and the number of ducklings produced per female were reduced
by the 4 and 8-μg/g dietary mercury treatments (that resulted in 5.9 and 14 μg/g mercury in their eggs, respectively). Ducklings
from parents fed the various mercury diets were just as heavy as controls at hatching, but by 6 days of age ducklings whose
parents had been fed 4 or 8 μg/g mercury weighed less than controls. Because we do not know if absorption of mercury from
our diets would be the same as absorption from natural foods, the mercury concentrations we report in eggs may be more useful
in extrapolating to possible harmful effects in nature than are the dietary levels we fed. We conclude that mallard reproduction
does not appear to be particularly sensitive to methylmercury. |
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