Young and old honeybee (Apis mellifera) larvae differentially prime the developmental maturation of their caregivers

Abstract

In eusocial insects, daughters rear the offspring of the queen to adulthood. In the honeybee, Apis mellifera, nurses rear young and old larvae, which emit divergent pheromones. These larval pheromones in turn affect nurse bee behaviour and physiology. To determine whether larvae and their associated pheromones have long-term physiological and behavioural effects (a priming influence) on nurse behaviour, we examined the effects on young workers of exposure to young larvae, old larvae or the young larval pheromone e-beta ocimene (eβ) relative to a broodless control population. We also tested whether exposing nurses to the volatile eβ pheromone of young larvae was sufficient by itself to produce physiological changes similar to those caused by exposure to live larvae. To disentangle the releaser and primer effects of brood pheromones on age of first foraging and collection bias, bees were primed for only the first 10 days of adult life. The early environment of maturing caregivers was found to alter the circulating titres of vitellogenin and juvenile hormone in nurses. Live brood treatments suppressed ovary activation. The brood environments also significantly reduced the age of first foraging, while priming with eβ increased the proportion of pollen foragers. Collectively, these results support the view that the reproductive regulatory network is sensitive to colony conditions, and this network is used to mediate the foraging division of labour.