The structure of courtship behavior in Drosophila males: Boundaries of plasticity

Abstract

The courtship ritual of Drosophila males toward females has been extensively studied to elucidate the mechanisms of behavioral plasticity in insects. Courtship is an innate, fixed sequence of behaviors that results in mating. The implementation of this instinct involves adjusting specific parameters of the courtship behaviors, such as sound production, to increase the likelihood of successful copulation. Moreover, courtship can be temporarily suppressed following an unsuccessful attempt with a previously mated female. While the neural mechanisms underlying courtship learning are well described, the interaction between male behavioral sequencing and known female-derived determinants of suppression (e.g., cVA from mated females and active rejection behaviors) remains unclear. In our study, we characterized the structure of male courtship towards virgin, mated, and immature females. We found that changes in the frequencies of transitions between courtship behaviors provide adaptive restructuring in the implementation of this ritual. Courtship towards mated females causes males to reinitiate the ritual more frequently, and we hypothesize that repeated unsuccessful initiations may ultimately result in courtship suppression. When courting immature females, males neither attempt copulation nor restart the ritual, which may explain the absence of courtship suppression with this type of female and raises the question of the evolutionary significance of courtship towards immature females.