Reproductive physiology mediates honey bee (Apis mellifera) worker responses to social cues

Abstract

Though social insect colonies are often considered to be models of cooperative behavior, there can be conflict between queens and their workers over reproduction. In honey bees (Apis mellifera), the queen releases a pheromone that attracts workers and inhibits worker ovary activation such that they remain sterile and rear the offspring of the queen. Furthermore, under queenless conditions, workers can rear new queens from the old queen’s eggs or activate their ovaries and lay their own eggs. Workers vary greatly in their ability to activate their ovaries, and this variation is positively correlated with ovary size. Here, we demonstrate that, compared to their sisters, workers with the larger ovaries are less attracted to queen pheromone, less likely to rear new queens if the old queen is lost, and more likely to activate their ovaries in the absence of a queen. Furthermore, surgically increasing a bee’s ovarian mass reduces her attraction to queen pheromone. The additional ovarian mass altered brain expression levels of the octopamine receptor, Oa1, but these differences did not correlate with response to queen pheromone. Overall, these results indicate that honey bee workers’ response to social cues under both queenright and queenless contexts is modified by their reproductive physiology, such that workers with greater ovary activation rates are less likely to engage in behaviors that promote the queen’s reproduction.