OVULATION STIMULATING SUBSTANCES IN DROSOPHILA BIARMIPES MALES - THEIR ORIGIN, GENETIC-VARIATION IN THE RESPONSE OF FEMALES, AND MOLECULAR CHARACTERIZATION

Ovulation responses of Drosophila biarmipes females to an injection of methanolic extract from conspecific males vary with the strains of fe males. This strain difference seems to be controlled by a small number of autosomal genes, with low responsiveness being recessive. Strangel y, all D. biarmipes strains show a high level of ovulation after matin g. We pursued the reason for this discrepancy and found that D. biarmi pes males produce two different substances with ovulation-inducing act ivity. One of them is derived from the accessory glands and effective in females of all strains. Another originates in the ejaculatory duct and is inactive in some strains. In an active HPLC fraction of the eja culatory duct extract, we found a peptide consisting of 32 amino acids . Its C-terminal region has a striking similarity to the sex-peptide o f D. melanogaster, but the N-terminal region was entirely different. E volutionary implications of these findings are discussed. (C) 1998 Els evier Science Ltd. All rights reserved.