Animals engage in a plethora of mutualistic interactions with microorganisms that can confer various benefits to their host but can also incur context-dependent costs. The sawtoothed grain beetle Oryzaephilus surinamensis harbors nutritional, intracellular Bacteroidetes bacteria that supplement precursors for the cuticle synthesis and thereby enhance desiccation resistance of its host. Experimental elimination of the symbiont impairs cuticle formation and reduces fitness under desiccation stress but does not disrupt the host’s life cycle. For this study, we first demonstrated that symbiont populations showed the strongest growth at the end of metamorphosis and then declined continuously in males, but not in females. The symbiont loss neither impacted the development time until adulthood nor adult mortality or lifespan. Furthermore, lifetime reproduction was not influenced by the symbiont presence. However, symbiotic females started to reproduce almost two weeks later than aposymbiotic ones. Thus, symbiont presence incurs a metabolic and context-dependent fitness cost to females, probably due to a nutrient allocation trade-off between symbiont growth and sexual maturation. The O. surinamensis symbiosis thereby represents an experimentally amenable system to study eco-evolutionary dynamics under variable selection pressures.

中文翻译：

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营养共生体在谷物害虫甲虫中延迟繁殖的代谢成本。

动物与微生物进行过多的交互作用，可以给宿主带来各种好处，但也会产生与环境有关的成本。锯齿状甲虫Oryzaephilus surinamensis带有营养的细胞内拟杆菌属细菌，可补充表皮合成的前体，从而增强宿主的抗干燥性。实验性消除共生体会损害角质层形成并降低干燥压力下的适应能力，但不会破坏宿主的生命周期。对于这项研究，我们首先证明了共生体种群在变态结束时显示出最强的生长，然后在雄性中持续下降，而在雌性中则没有。共生体的丧失既不影响成年前的发育时间，也不影响成年死亡率或寿命。此外，终生繁殖不受共生体存在的影响。但是，共生雌性比非共生雌性快两周开始繁殖。从而，共生体的存在会给女性带来新陈代谢和与环境有关的健身成本，这可能是由于共生体生长与性成熟之间的营养分配权衡所致。的因此，苏里南O.共生代表了一个实验上可适应的系统，用于研究在可变选择压力下的生态进化动力学。