Data from: Social immunity in honeybees—Density dependence, diet, and body mass trade‐offs

Group living is favourable to pathogen spread due to the increased risk of disease transmission between individuals. Similar to individual immune defences, social immunity, i.e. anti-parasite defences mounted for the benefit of individuals other than the actor, are predicted to be altered in social groups. The eusocial honey bee (Apis mellifera) secretes glucose oxidase (GOX), an antiseptic enzyme, throughout its colony, thereby providing immune protection to other individuals in the hive. We conducted a laboratory experiment to investigate the effects of group density on social immunity, specifically GOX activity, body mass and feeding behaviour in caged honey bees. Individual honey bees caged in a low group density displayed increased GOX activity relative to those kept at a high group density. In addition, we provide evidence for a trade-off between GOX activity and body mass: Individuals caged in the low group density had a lower body mass, despite consuming more food overall. Our results provide the first experimental evidence that group density affects a social immune response in a eusocial insect and that the previously reported trade-off between immunity and body mass extends to social immunity. GOX production appears to be costly for individuals, and potentially the colony, given that low body mass is correlated with small foraging ranges in bees. At high group densities individuals can invest less in social immunity than at low densities, whilst presumably gaining shared protection from infection. Thus, there is evidence that trade-offs at the individual level (GOX vs body mass) can affect colony-level fitness.

集群栖息会提升个体间的疾病传播风险，因此有利于病原体的扩散。与个体免疫防御类似，社会免疫（social immunity）——即个体为其他同类而非自身构建的抗寄生虫防御机制——据预测会在集群群体中发生改变。真社会性昆虫西方蜜蜂（Apis mellifera）会在整个蜂群中分泌葡萄糖氧化酶（glucose oxidase, GOX），这是一种抗菌酶类，能够为蜂巢内的其他个体提供免疫保护。本研究通过室内控制实验，探究了群体密度对笼养西方蜜蜂的社会免疫（具体为GOX活性）、体重与取食行为的影响。实验结果显示，与高群体密度笼养的蜜蜂个体相比，低群体密度笼养个体的GOX活性显著升高。此外，本研究还为GOX活性与体重间的权衡关系提供了实验证据：尽管低群体密度笼养个体的整体取食量更高，但其体重却更低。本研究结果首次通过实验证实，群体密度会影响真社会性昆虫的社会免疫应答，且此前报道的免疫与体重间的权衡关系同样适用于社会免疫。鉴于蜜蜂的体重偏低与其觅食范围狭小存在关联，GOX的合成对个体乃至整个蜂群而言似乎都存在代价。在高群体密度下，个体相较于低密度群体可减少对社会免疫的投入，同时大概率能获得群体共享的感染防护。因此，有证据表明个体层面的权衡关系（GOX活性与体重间的权衡）会对蜂群的适合度产生影响。