Conditioned courtship inDrosophila and its mediation by association of chemical cues

Abstract

AlthoughDrosophila melanogaster males usually court virgin females vigorously, a male will perform very little courtship in response to a virgin female if he has previously been in the presence of a fertilized female. The normal courtship response is restored after approximately 3 h [Siegle, R. W., and Hall, J. C. (1979).Proc. Natl. Acad. Sci. USA 76:3430–3434]. Experiments designed to account for this phenomenon exclude the possibilities that the visible “rejection” behaviors performed by the fertilized female in response, to the male are either a necessary or a sufficient basis for the transitory decrement in courtship. A role for other visual, cues is also ruled out. However, mutant males with olfactory defects do court virgins after experiences with fertilized females. Also, males exposed to extracts from fertilized females while in the presence of a male or virgin female fly thereafter perform very little courtship with virgin females. Finally, we describe a new mutant strain whose males court and mate with wild-type, virgin females normally; but after such a mating, the wild-type female is readily courted by a wild-type male, and that male subsequently exhibits vigorous courtship of other females. Since both virgin and fertilized females can stimulate males to court them, these observations fuggest the following hypothesis. After fertilization by a wild-type male, a female becomes a source of an aversive chemical cue which is sensed by a courting male [cf. Tompkins, L., and Hall, J. C. (1981).J. Insect Physiol. 27:17–21]. The courting male associates that substance with the courtship-stimulating cues emanating from females which he subsequently encounters, and he therefore learns to avoid courting these females.