Genetic variation in the susceptibility to mercury and other metal compounds in Drosophila melanogaster.

The tolerance of Drosophila melanogaster to heavy metal compounds was investigated with special emphasis on methylmercury. A pronounced variation in tolerance to CH3HgOH, HgCl2, (C2H5)3PbCl, (CH3)3SnCl, and CdCl2 was recorded between 12 wild-type strains. After ranking the tolerance of the strains with respect to the five compounds rank correlations for experiments within and between compounds were calculated. The results showed a high degree of correlation within compounds but no unequivocal indication of a correlation between compounds, indicating that different mechanisms of genetic control for tolerance were operating for the five compounds. Rank correlations for experiments with 12 different mercury, lead, tin, and cadmium compounds and the same 12 wild-type strains only indicated one significant correlated response, between tripropyltin and tributyltin. A selection experiment for tolerance to methylmercury was performed with a foundation population, synthesized from four wild-type strains, showing a high initial tolerance. One control and two levels of treatment doses were used. A distinct selection response was obtained and a high tolerance was reached particularly for the high-dose selection line after 12 generations, when the experiment ended. Genetic analysis of the tolerance indicated a dominant and polygenic inheritance. Investigation of the uptake and excretion of CH3Hg203OH showed that the level of tolerance to methylmercury was correlated with the uptake of the mercury but apparently not with the rate of excretion. Cystein increased the susceptibility to methylmercury. Inorganic mercury and trimethyl lead exhibited a synergistic toxic effect, evidently as the result of an in vitro transmethylation of mercury. A high somatic susceptibility to methylmercury also applied to the induction of nondisjunction and sex-linked recessive lethals.