Primer effects of the honeybee, Apis mellifera, queen pheromone 9-ODA on drones

In many social insect species, pheromones coordinate defining features of social life. Queen-produced pheromones mediate many of these processes, and thus there is substantial interest in understanding both the mechanisms by which queen pheromones organize behaviour and how these chemical communication systems evolved. It is hypothesized that queen social pheromones evolved from sex pheromones found in their solitary ancestors. Here we begin to test this theory in the honeybee, where the queen-produced pheromone 9-ODA (9-oxo-2-decenoic acid) serves as both a social pheromone (priming physiological processes mediating worker behavioural maturation) and sex pheromone (attracting males during mating flights). While we expected the primer effects of 9-ODA on workers to represent a derived worker-specific function, we surprisingly found similar effects in drones. Exposure to 9-ODA resulted in a significant increase in expression levels of vitellogenin in drones. Since previous studies in workers found that vitellogenin levels regulate behavioural maturation, we investigated 9-ODA's effects on sexual maturation in drones. Drones exposed to 9-ODA initiated mating flights later and took fewer flights than control drones. Our results demonstrate that honeybee queen pheromone has primer effects on drone bees, and thus chemical communication systems involving honeybee drones are more complex than previously appreciated.