Data from: Seasonality, alarm pheromone and serotonin: insights on the neurobiology of honeybee defence from winter bees

Honeybees maintain their colony throughout the cold winters, a strategy that enables them to make the most of early spring flowers. During this period, their activity is mostly limited to thermoregulation, while foraging and brood rearing are stopped. Less is known about seasonal changes to the essential task of defending the colony against intruders, which is regulated by the sting alarm pheromone. We studied the stinging responsiveness of winter bees exposed to this scent or a control (solvent). Surprisingly winter bees, while maintaining their responsiveness in control conditions, did not increase stinging frequency in response to the alarm pheromone. This was not due to the bees not perceiving the pheromone, as shown by calcium-imaging of the antennal lobes. Since the alarm pheromone is thought to act through an increase in brain serotonin levels, ultimately causing heightened defensiveness, we checked if serotonin treatments would affect the stinging behaviour of winter bees. Indeed, treated winter bees became more inclined to sting. Thus, we postulate that loss of responsiveness to the sting alarm pheromone is based on a partial or total disruption of the mechanism converting alarm pheromone perception into high serotonin levels in winter bees.

蜜蜂可在寒冷冬季维持蜂群存续，这一策略使其得以充分利用早春花期资源。此阶段蜂群活动主要局限于体温调节，觅食与育幼行为均处于停滞状态。人们对蜂群防御入侵者这一核心任务的季节性变化知之甚少，而该防御行为受螫刺报警信息素（sting alarm pheromone）调控。本研究针对暴露于该信息素或对照溶剂（solvent）的越冬蜂的螫刺反应性展开探究。令人意外的是，越冬蜂在对照条件下仍保有反应性，但在接触报警信息素后并未提升螫刺频次。触角叶（antennal lobes）的钙成像实验表明，该现象并非源于蜜蜂无法感知该信息素。鉴于现有研究认为报警信息素通过提升脑部血清素（serotonin）水平发挥作用，最终增强蜂群防御性，本研究验证了血清素处理是否会影响越冬蜂的螫刺行为。实验结果确证，经血清素处理的越冬蜂螫刺意愿显著提升。据此，我们推测越冬蜂对螫刺报警信息素的反应性丧失，源于其将信息素感知转化为脑部高血清素水平的机制出现了部分或完全紊乱。