GENETIC-EVIDENCE THAT OVULATION REDUCES SEXUAL RECEPTIVITY IN DROSOPHILA-MELANOGASTER FEMALES

Drosophila females start ovulation shortly after mating, and at the sa me time they become unreceptive to courting males. Both physiological changes are induced by the ''sex-peptide'' derived from the male acces sory glands. It is conceivable, therefore, that the first effect of th e peptide is to induce ovulation, and some signal derived from ovulate d eggs makes females unreceptive. To test this hypothesis, I examined the mating receptivity of virgin D. melanogaster females homozygous fo r lozenge mutants that showed a high-frequency spontaneous ovulation. These females were reluctant to mate. However, when mature eggs were g enetically deprived using nonallelic female sterile mutants,their rece ptivity increased significantly, although mating speed was still slowe r than that of normal virgin females. Essentially the same was found w ith the females that were ectopically expressing the sex-peptide gene. The results indicate that ovulation induced by the sex-peptide has an effect of reducing the sexual receptivity of mated females.