Female Olfactory Sensitivity Is Temporally Asynchronous with Male Courtship in a Butterfly

Signal efficacy is crucial to communicative behaviours. To be effective, a signal once broadcast must be capable of being received and interpreted by a receiver or receivers. In addition to maximizing the amount that a signal stimulates receptive organs, optimally the timing of when a signal is broadcast would synchronize with a receivers peak receptivity. Here, we investigated whether peak timing of male courtship, which includes release of a pheromone required for copulation to occur, is synchronized with female pheromone sensitivity in the butterfly Bicyclus anynana. To do this, we performed behavioural and electrophysiological assays at dawn, noon, and dusk. We also investigated the circadian rhythmicity of antennae gene expression by performing RNA-Sequencing on antennae tissues collected at dawn, noon and dusk. We found that although males court most often near dusk, females are more sensitive to odorants in the morning. Furthermore, antennae exhibited differential and diurnally rhythmic expression of odorant receptors and genes associated with learning and sexual receptivity, as well as GO terms related to fatty acid metabolism and trehalose biosynthesis, supporting our circadian electrophysiological results. Previous literature indicates females form both positive and negative associations with male pheromones in the morning, regardless of whether males court females. Thus, this asynchrony may enable female B. anynana to learn mate preferences before they are courted by conspecific (or potentially heterospecific) males.