The impact of QMP on sexual fitness of male Drosophila melanogaster and the extent to which the effect of QMP is mediated by FOXO in the male Drosophila testes

Eusocial species exhibit high levels of complexity and a reproductive division of labour. One of the primary enforcers of reproductive division of labour in Apis mellifera is the production of Queen Mandibular Pheromone (QMP) by the queen. This reproductively restricts the female workers and excites the male drones to mate. Despite a divergence of ~330 million years, QMP also reproductively represses female Drosophila melanogaster and does not impact reproduction in males.

This study aimed to further analyse the degree of sex based differences in response to QMP in Drosophila and identify if low levels of FOXO in the testes mediate the reproductive resistance of males to QMP. We used feeding assays, performed with optical density and semi-quantitative analysis; fluorescence-based visualisation of insulin expression; mating assays and activity monitoring.

We found that QMP increases feeding in males during, but not following, exposure, possibly due to a full crop reducing the ability to further feed. QMP also reduces the activity of male Drosophila. Additionally, low FOXO does not seem to prevent the induction of starvation-like responses in the testes and finally, that the somatic support cells may allow sperm to develop insensitive to nutrition due to low FOXO levels.

The similarity of the sex based differences found between A. mellifera and D. melanogaster may indicate that the path of action of QMP acts through highly conserved signalling systems that differ by sex. This work contributes to the broader understanding of these social systems allowing for greater comprehension of one of the primary signalling systems in one of the most complex social species, contributing to the understanding of the factors that may have facilitated the development of such complexity.