Camponotus floridanus ants incur a trade-off between phenotypic development and pathogen susceptibility from their mutualistic Endosymbiont Blochmannia

Various insects engage in microbial mutualisms in which the reciprocal benefits exceed the costs. Ants of the genus Camponotus benefit from nutrient supplementation by their mutualistic endosymbiotic bacteria, Blochmannia, but suffer a cost in tolerating and regulating the symbiont. This cost suggests that the ants face secondary consequences such as susceptibility to pathogenic infection and transmission. In order to elucidate the symbiont’s effects on development and disease defence, Blochmannia floridanus was reduced in colonies of Camponotus floridanus using antibiotics. Colonies with reduced symbiont levels exhibited workers of smaller body size, smaller colony size, and a lower major-to-minor worker caste ratio, indicating the symbiont’s crucial role in development. Moreover, these ants had decreased cuticular melanisation, yet higher resistance to the entomopathogen Metarhizium brunneum, suggesting that the symbiont reduces the ants’ ability to fight infection, despite the availa...多种昆虫均存在互惠收益高于成本的微生物共生关系。弓背蚁属（Camponotus）蚂蚁可通过其共生的内共生细菌布洛赫曼菌（Blochmannia）获得营养补充，但需付出耐受与调控该共生体的代价。这一代价提示，蚂蚁会面临次生后果，例如对病原感染与传播的易感性上升。为阐明该共生体对宿主发育与疾病防御的影响，研究人员通过抗生素处理佛罗里达弓背蚁（Camponotus floridanus）的蚁群，降低了其体内佛罗里达布洛赫曼菌（Blochmannia floridanus）的丰度。共生体丰度降低的蚁群，其工蚁体型更小、蚁群整体规模更小，且大工蚁与小工蚁的品级比例更低，这表明该共生体在蚂蚁发育过程中发挥关键作用。此外，该类蚂蚁的体壁黑化（cuticular melanisation）程度下降，但对昆虫病原物（entomopathogen）布氏白僵菌（Metarhizium brunneum）的抗性反而升高，这提示该共生体虽会削弱蚂蚁的抗感染能力，尽管[原文内容未完整呈现]。