Response of puffing pattern to in vivo treatments with organomercurials in Drosophila melanogaster.

Abstract

Survival rate and length of development time were used as indicators of toxicity of methoxyethylmercuric acetate, methoxyethylmercuric chloride and methylmercuric chloride in Drosophila melanogaster. The two methoxyethyl compounds exhibit toxic effects (prolongation of development time) only in the highest concentration tested (10.0 mg Hg/l), while methylmercury already has toxic effects (lethality and prolongation of development) in concentrations of ≥ 1.25 mg Hg/l. Similar concentrations were used to test the effects of mercuric compounds on genetic balance in 0-hour prepupae, as revealed by the puffing patterns of polytene salivary chromosomes. Four aspects of puffing pattern response were observed in 20% of the 300 inspected larvae: (1) regression of total gene activity, expressed in terms of decreases in puff sizes/chromosome, (2) inhibition of normal puff regression, characterized by puff activity in 2B, 74EF, 75B and 78D which, during normal development, should be regressed by this stage, (3) inhibition of normal puff activation, which is characterized by puffs 3A, 4F, 28A, 46F, 61C, 62C, 62F and 73B being inactive, though they normally should be induced by this stage, and (4) induction of a new locus (45AB) which is not normally observed in a puffed state. Changes in the puffing pattern have been observed when all three mercuric compounds were used, but mainly in concentrations ≥ 1.25 mg Hg/l. Consequently, puffing pattern response does not necessarily correlate with toxic concentrations; instead, the variability in puff response between individuals seems to indicate interindividual variations in sensitivity to mercuric compounds.