Vitellogenin plays a role in regulating honey bee swarming

Swarming, or colony reproduction, in honey bees (Apis mellifera) is an indicator of colony-level fitness. The drivers of swarming remain elusive at both the colony and individual bee level. Floral abundance, rapid colony growth, and congestion are colony correlates and partial triggers of swarming but are not singularly causal. The nutritional and physiological state of individual bees within colonies preparing to swarm has been understudied. We hypothesized that vitellogenin (Vg), a phospholipoglycoprotein that influences the honey bee age-based division of labor in individual bees, might also mediate the cascade of physiological and behavioral processes that lead to reproductive swarming. Over two years, we compared vitellogenin(Vg) gene expression levels in age-marked worker bees sampled at various intervals before a swarm (pre-swarming colonies) to samples of same-aged bees collected from non-swarming colonies at the same time intervals. Vg levels were significantly higher in 10- and 14-day old bees from pre-swarming colonies three days prior and within 24 h of swarm issuance. Vg levels normally decrease in 10-14d old bees that are transitioning to the forager behavioral state. We provide a hypothesis for how Vg levels in individual bees might influence the colony-level regulatory processes that lead to swarming. This work may show for the first time, the link between a highly conserved protein associated with individual reproduction across oviparous animal taxa and its function as a mechanism of social reproduction in honeybees colonies.