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The reproductive resistance of mallards (Anas platyrhynchos) to the toxic effects of methyl mercuric chloride was studied over four generations. A control group and a highline group of 30 breeding pairs each of “game farm”-type mallards were developed from a parental generation, P1, of 29 pairs of birds. The test was divided into a 4-week pretreatment and a 4-week posttreatment period. The progeny for subsequent generations were obtained during the pretreatment period and based on individual female performance during the posttreatment period. The highline breeders were selected on the basis of the highest percentage survival of ducklings from fertile eggs after a treatment of two doses of 8 mg methyl mercuric chloride in a 2-week interval. A range of 350 to 600 eggs per test period was processed for each line. Survival of the ducklings in the P1 generation was 57 and 12 percent for the pretreatment and posttreatment periods, respectively. Survival of the ducklings from the control birds ranged between 38 and 56 percent and from 53 to 72 percent for the highline birds. Posttreatment survival ranged from 14 to 25 percent for the control and 22 to 38 percent for the highline females. Separation of the percentage of ducklings that survived between the control and highline birds occurred in the F1 generation and tended to increase slightly. Earlier hatch times were noted in the later generations of the highline compared with the control ducklings.
mallard, methyl mercuric chloride, toxicity, selection, genetic response, hatchability, survival, reproduction, toxicology, wildlife
Professor, Michigan State University, East Lansing, Mich.