Formica fusca ants use aphid supplemented foods to alleviate effects during the acute phase of a fungal infection

The modulation of nutritional intake by animals to combat pathogens is a behaviour which is getting increasing attention. Ant studies using isolated compounds or nutrients in artificial diets have revealed a lot of the dynamics of the behaviour, but natural sources of medicine are yet to be confirmed. Here we explored whether Formica fusca ants exposed to a fungal pathogen can use an artificial diet containing foods spiked with different concentrations of crushed aphids for a medicinal benefit. We show that pathogen exposed colonies adjusted their diet to include more aphid supplemented foods during the acute phase of the infection, reducing the mortality caused by the disease. However, the benefit was only attained when having access to a varied diet, suggesting that while aphids contain nutrients or compounds beneficial against infection, it is a part of a complex nutritional system where costs and benefits of compounds and nutrients need to be moderated.

Methods
Ant nests (Formica fusca) were collected and given unique ID's

For experiments original nests were split into experimental colony fragments (80 workers/fragment) to be used in the different infection treatments (Sham treated Control or exposed to a fungal pathogen (Beauveria bassiana)). Each experimental colony were then given a diet consisting of three different concentrations of supplemented aphids (Megaoura viciae): High concentration, low concentration, standard food (no aphids)). Foraging arenas were photographed 5 times a day for 9 days, from which each foraging ant was counted on the specific foods. Dead and alive ants were counted at the end of the 9 day period.

For the second part, we split original nests into 4 experimental colony fragments to be used in different treatment diet combinations (Control - Standard food, Control - High concentration food, Exposed - Standard food, Exposed High concentration food). Dead ants were counted daily for 9 days.

All data processing and analysis was done using R.

动物为抵御病原体而调节营养摄入的行为正受到日益广泛的关注。此前，借助人工饲料中的分离化合物与营养物质开展的蚂蚁相关研究已阐明该行为的多项动态特征，但天然药用物质来源仍未得到证实。本研究探究了被真菌病原体感染的黑褐蚁（Formica fusca）能否通过喂食添加不同浓度碾碎蚜虫的人工饲料获得药用益处。研究结果显示，受感染的蚁群在感染急性期会调整饮食，增加蚜虫补充饲料的摄入比例，从而降低该病害导致的死亡率。但该益处仅在可获得多样化饲料的情况下才能实现，这表明尽管蚜虫含有对抗感染的营养物质或化合物，但这只是复杂营养系统的一部分，该系统中各类化合物与营养物质的成本与收益需要得到协调平衡。

材料与方法
采集黑褐蚁（Formica fusca）蚁巢，并为每个蚁巢赋予唯一标识编号。
实验阶段，将原始蚁巢拆分为实验蚁群片段（每片段含80只工蚁），用于不同感染处理组：假处理对照组，以及被球孢白僵菌（Beauveria bassiana）感染的处理组。随后，为每个实验蚁群提供三种不同浓度的蚜虫补充饲料（Megaoura viciae）：高浓度组、低浓度组，以及标准饲料组（无蚜虫添加）。在9天的实验周期内，每日对觅食区域进行5次拍照，统计在特定饲料上觅食的蚂蚁数量。实验结束时统计存活与死亡的蚂蚁数量。
第二部分实验中，我们将原始蚁巢拆分为4个实验蚁群片段，用于不同饲料组合的处理组：对照组-标准饲料、对照组-高浓度饲料、感染组-标准饲料、感染组-高浓度饲料。在9天的实验周期内每日统计死亡蚂蚁数量。
所有数据处理与分析均通过R语言完成。