Exploring how starvation and insulin regulate olfactory preference in Apis cerana cerana

The olfactory senses of Apis cerana cerana are crucial to their essential activities. This study aimed to investigate the effect of phased starvation, insulin injections and insulin silencing on the olfactory abilities of A. cerana cerana. A starvation regression curve was established; it was found that the mortality of bees increased significantly after 9 h of starvation. Measurement of insulin levels in the bees revealed a gradual decrease after 3 and 6 h of starvation, followed by a sudden rise at 9 h. Additionally, starvation induced changes in the olfactory responses of bees: starvation decreased the electroantennogram values of antennae for most odorants, changed behavioral preferences for some floral odorants and affected the expression of olfactory genes. High insulin levels enhanced electroantennogram response values of the antennae, changing most odorant selections from attraction or neutrality to avoidance. In contrast, low insulin levels decreased the electroantennogram response values of the antennae and predominantly shifted odor preferences toward attraction. These two insulin conditions resulted in opposite results, and changes in olfactory gene expression also exhibited differing trends. It was found that low-insulin conditions caused by starvation for 3 h and 6 h as well as insulin silencing exhibited similarities in multiple olfactory metrics. This suggests that starvation-induced olfactory changes may be attributed to the reduction of endogenous insulin levels. The study results reveal a strong correlation between insulin and olfaction in A. cerana cerana, providing a foundation for future investigations into the underlying regulating mechanisms of insulin/insulin-like signaling on olfaction. These findings also offer research directions for enhancing bee pollination capacity and regulating other olfactory behaviors.