Nest architecture is a fundamental character shaping immune strategies of social insects. The arboreal ant Temnothorax unifasciatus nests in cavities such as oak galls where the entire colony lives in a unique small chamber. In these conditions, physiological and behavioural strategies likely prevail over compartmentalisation and are presumably tuned with colony size. We designed two experiments to study chemical and behavioural immune strategies against the entomopathogenic fungus Metarhizium anisopliae in colonies of different sizes. First, we compared spore germination and length of germinal tubes inside artificial nests, designed to impede the contact between the ants and the fungus, in colonies of different size. In the absence of direct contact, Temnothorax unifasciatus colonies inhibit fungal growth inside their nests, presumably through volatile compounds. The analysis revealed a positive correlation between fungistatic activity and colony size, indicating that workers of smaller colonies do not invest a higher per capita effort in producing such substances compared to larger colonies. Second, we performed a removal experiment of contaminated and non-contaminated items introduced inside the nests of colonies of different size. Small colonies challenged with contaminated fibres showed an increased removal of all the items (both contaminated and non-contaminated) compared to small colonies challenged with non-contaminated fibres only. Conversely, larger colonies moved items regardless of the presence of the spores inside the nest. Colony size qualitatively affected removal of waste items showing a pathogen elicited reaction in small colonies to optimise the reduced workforce, while the removal behaviour in larger colonies revealed to be expressed constitutively.

中文翻译：

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橡树胆中的家政学：针对Temnothorax蚁巢中真菌病原体的行为和化学免疫策略

巢式建筑是塑造社交昆虫免疫策略的基本特征。树栖蚂蚁Temnothorax unifasciatus筑巢于诸如橡树胆的洞中，整个殖民地都生活在一个独特的小房间里。在这些情况下，生理和行为策略可能会优先于隔离，并可能会根据菌落的大小进行调整。我们设计了两个实验，研究在不同大小的菌落中针对昆虫病原真菌Metanhizium anisopliae的化学和行为免疫策略。首先，我们比较了人工巢中孢子的萌发和发芽管的长度，这些巢旨在阻止蚂蚁和真菌在大小不同的菌落之间的接触。在没有直接联系的情况下，特发性坦胸菌落可能通过挥发性化合物抑制其巢内的真菌生长。分析显示，抑菌活性与菌落大小之间呈正相关，表明与大菌落相比，小菌落的工人在生产此类物质上的人均投入较高。其次，我们对引入不同大小的菌落巢中的受污染和未受污染的物品进行了清除实验。与仅受未污染纤维攻击的小菌落相比，受污染纤维攻击的小菌落显示出所有物品（受污染和未污染）的去除率增加。相反，无论巢中是否存在孢子，较大的菌落都会移动物品。