Data from: A carbohydrate-rich diet increases social immunity in ants

Increased potential for disease transmission among nest-mates means living in groups has inherent costs. This increased potential is predicted to select for disease resistance mechanisms that are enhanced by cooperative exchanges among group members, a phenomenon known as social immunity. One potential mediator of social immunity is diet nutritional balance because traits underlying immunity can require different nutritional mixtures. Here, we show how dietary protein–carbohydrate balance affects social immunity in ants. When challenged with a parasitic fungus Metarhizium anisopliae, workers reared on a high-carbohydrate diet survived approximately 2.8× longer in worker groups than in solitary conditions, whereas workers reared on an isocaloric, high-protein diet survived only approximately 1.3× longer in worker groups versus solitary conditions. Nutrition had little effect on social grooming, a potential mechanism for social immunity. However, experimentally blocking metapleural glands, which secrete antibiotics, completely eliminated effects of social grouping and nutrition on immunity, suggesting a causal role for secretion exchange. A carbohydrate-rich diet also reduced worker mortality rates when whole colonies were challenged with Metarhizium. These results provide a novel mechanism by which carbohydrate exploitation could contribute to the ecological dominance of ants and other social groups.

巢伴间疾病传播风险的提升，意味着群居生活存在固有代价。这种传播风险的提升被认为会筛选出可通过群体成员间协作交流增强的疾病抵抗机制，这一现象被称为社会免疫（social immunity）。社会免疫的潜在介导因子之一是膳食营养平衡，因为免疫相关的性状往往需要不同的营养组合。本研究揭示了膳食蛋白质-碳水化合物平衡如何影响蚂蚁的社会免疫：当被寄生真菌绿僵菌（Metarhizium anisopliae）侵染时，取食高碳水化合物膳食的工蚁，在群体环境中的存活时长约为单独饲养时的2.8倍；而取食等热量高蛋白膳食的工蚁，在群体环境中的存活时长仅为单独饲养时的1.3倍。营养水平对作为社会免疫潜在机制的社交梳理（social grooming）几乎无影响。然而，通过实验阻断分泌抗生素的后胸侧板腺（metapleural glands）后，群体饲养和营养对免疫的影响完全消失，这表明分泌物交换在其中发挥了因果性作用。当整个蚁群受到绿僵菌侵染时，高碳水化合物膳食同样降低了工蚁的死亡率。本研究结果揭示了一种全新的机制：碳水化合物的利用可助力蚂蚁及其他社会群体获得生态优势。