Impact of dietary treatments on longevity and body weight of Apis mellifera winter bees

In eusocial honey bees, Apis mellifera, diet, gut microbiota and nestmates can all contribute to the health of freshly-emerged individual workers, but their relative importance for longevity and body weight is currently unknown. Here, we show that diet is most relevant, followed by gut microbiota and the presence of nestmates. Freshly emerged workers were randomly assigned to eight treatments (with or without honey/pollen, protein-substitute lactalbumin, antibiotic tetracycline and nestmates for 24 h) and maintained under standardized laboratory conditions. Longevity and food consumption were measured daily and fresh body weight was assessed at day seven. The data show a significantly better survival and a higher body weight in workers supplied with honey/pollen. Survival was higher in the lactalbumin treatments compared to the ones restricted to sucrose only, but lower compared to those with honey/pollen, highlighting the importance of micronutrients. In contrast, antibiotic treatment had a significant negative effect on longevity and body weight, which may be explained by inactivated gut microbiota and/or toxicity of the antibiotics. There was no positive effect of nestmates, probably due to the short exposure period. In contrast, nestmates showed a negative effect on survival in antibiotic-treated workers, possibly by transmitting pathogens and antibiotic-induced gut dysbiosis. In conclusion, a macro- and micronutrient-rich diet appears to be the key to individual honey bee worker health. Providing an optimal diet and possibly gut microbiota appears to be a promising way to promote managed A. mellifera health.

在真社会性蜜蜂中，西方蜜蜂（Apis mellifera）的饮食、肠道菌群（gut microbiota）与巢友均可影响新羽化工蜂的健康，但目前尚不清楚这三者对工蜂寿命与体重的相对重要性。本研究结果显示，饮食的影响最为显著，其次为肠道菌群与巢友的存在。本研究将新羽化工蜂随机分为8个处理组，各处理组分别设置有无蜂蜜/花粉、蛋白替代物乳清蛋白（lactalbumin）、抗生素四环素（tetracycline）以及是否接触巢友，处理时长为24小时，随后将工蜂置于标准化实验室条件下饲养。每日记录工蜂的寿命与食物消耗量，并在第7天时测定其鲜体重。数据显示，饲喂蜂蜜/花粉的工蜂存活率与鲜体重均显著更高。饲喂乳清蛋白的处理组存活率高于仅饲喂蔗糖的组别，但低于饲喂蜂蜜/花粉的组别，这凸显了微量营养素的重要性。与之相反，抗生素处理对工蜂寿命与体重存在显著负面影响，这或许可归因于肠道菌群被灭活以及/或抗生素本身的毒性。巢友未表现出正向影响，这可能与暴露时长较短有关。但在经抗生素处理的工蜂中，巢友却对其存活率产生了负面影响，这可能是通过传播病原体以及抗生素诱导的肠道菌群失调（gut dysbiosis）所致。综上，富含宏量与微量营养素的饮食似乎是维持西方蜜蜂工蜂个体健康的关键。提供最优饮食及适宜的肠道菌群，或许是提升人工饲养西方蜜蜂健康水平的可行途径。