Exploiting the plasticity in social life history; physiology of extreme longevity in honeybee diutinus workers

Our studies have documented direct effects of vitellogenin on stress resistance and longevity during summer. However, although vitellogenin RNAi in workers living under favorable ambient conditions provides functional insight, it does not directly address the role of vitellogenin in extreme worker longevity. Diutinus bees normally develop at the onset of the unfavorable season (winter) in temperate climates and have lifespans comparable to queens (about 1 year). They represent a subcaste adaptation specif ic to Apis mellifera mellifera and A. m. carnica (North European) races, being absent from bees of African origin. Diutinus bees have very high vitellogenin titers. This physiology develops in the absence of brood, when less vitellogenin and vitellogenin derived products are transferred from nurse bees. However, there is also a lack of brood pheromone in wintering colonies. Brood pheromone affects worker behavior, physiology and gene expression, and recent results from Drosophila demonstrate that lifespan can be modulated by odors alone. Previous studies further have established that JH titers are low in workers, including foragers, immediately prior to wintering. It is unclear if these low JH levels are vitellogenin-dependent, or if they feed into a sepa rate pathway that also affects longevity. We will decouple these factors to understand the role of vitellogenin in extreme life spans, and also determine to what extent the winter survival of worker bees constitutes a no-cost extension of life.