Sexual conflict

What determines male mating rate? New research is highlighting the potential importance of variation in reproductive organ size in determining the limits of male mating frequency and reproductive success. The accessory glands provide the material required to synthesise the spermatophore in which the sperm, produced by the testes, are packaged. Male mating rate is both phenotypically and genetically correlated with the size of male accessory glands, but not of the testes. Furthermore, mating causes a significant short-term decrease specifically in accessory gland size. In other Diptera, the accessory glands produce substances that alter female behaviour and physiology, as well as structural proteins that may correspond to those forming spermatophores. Current research with stalk-eyed flies is focussed on identification of accessory gland products and evaluating their role in mediating potential conflicts of interest between the sexes.