The dynamic terminal investment threshold model posits that the propensity of an individual to terminally invest in response to an immediate survival threat, such as an infection, depends on other factors that alter an individual's residual reproductive value. Here, we explore the potential for dynamic terminal investment in burying beetles, insects that inter small vertebrate carcasses as the sole source of food for their offspring and that exhibit extensive biparental care. We injected males at two different ages with heat-killed bacteria and measured their reproductive output, predicting that immune-challenged males would show a longer period of parental care, consume less of the carcass and produce a greater number of larvae in the current reproductive attempt compared with control males. We further predicted that terminal investment would be more evident in older males than in younger ones. Males challenged with heat-killed bacteria as virgins prior to their first reproductive attempt showed no evidence of terminal investment, whereas these same individuals when challenged at a later age as reproductively experienced breeders in a subsequent reproductive attempt showed increased reproductive output. Older, immune-challenged individuals gained less mass during the time on the carcass than control males, suggesting that this terminal investment was subsidized, at least in part, by males refraining from eating as much of the carcass as they might have otherwise done in the absence of an immune challenge, leaving more carrion for their offspring to consume at the expense of their own maintenance and future reproduction. Because it seems likely than an individual's residual reproductive value decreases with both increasing age and reproductive experience, the context-specific terminal investment shown by immune-challenged males in the current study aligns with theory.

中文翻译：

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雄性埋藏甲虫的动态终端投资

动态终端投资阈值模型假设，个人为应对直接生存威胁（例如感染）而进行终端投资的倾向取决于改变个人剩余生殖价值的其他因素。在这里，我们探索了埋藏甲虫的动态终端投资潜力，这种昆虫在小型脊椎动物尸体中作为其后代的唯一食物来源，并表现出广泛的双亲照顾。我们给两个不同年龄的雄性注射了热灭活细菌并测量了它们的繁殖量，预测免疫受到挑战的雄性会表现出更长的父母照顾时间，消耗更少的尸体并在当前的生殖尝试中产生更多的幼虫与对照男性相比。我们进一步预测，老年男性的终端投资将比年轻男性更明显。雄性在第一次生殖尝试之前作为处女受到热灭活细菌的挑战没有显示出最终投资的证据，而这些相同的个体在随后的生殖尝试中作为有生殖经验的繁殖者受到挑战时表现出增加的生殖产量。年长的、免疫受到挑战的个体在屠体期间获得的体重少于对照雄性，这表明这种最终投资至少在一定程度上得到了补贴，因为雄性避免吃掉他们在其他情况下可能会吃的尸体。缺乏免疫挑战，为后代留下更多腐肉，以牺牲其自身的维持和未来的繁殖为代价。