Dissection of signalling modalities and courtship timing reveals a novel signal in Drosophila saltans courtship

Courtship signalling, necessary for the recognition of potential mates, is often complex, using many modalities with multiple components. Drosophila courtship comprises chemical, tactile, visual and acoustic stimuli. Ablation of single sensory channels, either signal production or reception, can determine the roles of individual modalities in overall reproductive success. Adding measures of courtship timing, particularly courtship latency, the time for the male to initiate courtship, and courtship duration, the time from courtship initiation until the female accepts the male for copulation, allows us to identify the stage of courtship at which a signal acts. This study focuses on Drosophila saltans, a member of the saltans species group. Little is known about sexual behaviour of species in this group, part of the Sophophora subgenus. In the present study, we found that ablation of any one signal in D. saltans did not eliminate mating, thus courtship is multimodal. In addition to examining the signals and signal reception common to most Drosophila species, we also examined the role that the midtarsi play in courtship. The removal of the female's midtarsi significantly reduced mating occurrence. Using timing data, we discerned that the absence of midtarsi in the female did not affect the male's ability to identify the female as a potential mate, but the male may be unable to sufficiently stimulate the female to copulation. Measuring courtship latency and courtship duration, as well as the occurrence of courtship and copulation, allowed us to determine whether a particular signal plays a role in activating the male to initiate courtship or stimulating the female to mate.