Sikkink Kristin L, Bailey Nathan W, Zuk Marlene, Balenger Susan L
Department of Biology University of Mississippi Oxford MS USA.
Centre for Biological Diversity School of Biology University of St Andrews St Andrews UK.
Ecol Evol. 2020 Oct 26;10(23):13312-13326. doi: 10.1002/ece3.6930. eCollection 2020 Dec.
Among the parasites of insects, endoparasitoids impose a costly challenge to host defenses because they use their host's body for the development and maturation of their eggs or larvae, and ultimately kill the host. Tachinid flies are highly specialized acoustically orienting parasitoids, with first instar mobile larvae that burrow into the host's body to feed. We investigated the possibility that field crickets employ postinfestation strategies to maximize survival when infested with the larvae of the parasitoid fly . Using crickets from the Hawaiian Islands of Kauai, where the parasitoid is present, and crickets from the Cook Islands (Mangaia), where the parasitoid is absent, we evaluated fitness consequences of infestation by comparing feeding behavior, reproductive capacity, and survival of males experimentally infested with larvae. We also evaluated mechanisms underlying host responses by comparing gene expression in crickets infested with fly larvae for different lengths of time with that of uninfested control crickets. We observed weak population differences in fitness (spermatophore production) and survival (total survival time postinfestation). These responses generally did not show an interaction between population and the number of larva hosts carried or by host body condition. Gene expression patterns also revealed population differences in response to infestation, but we did not find evidence for consistent differences in genes associated with immunity or stress response. One possibility is that any postinfestation evolved resistance does not involve genes associated with these particular functional categories. More likely, these results suggest that coevolution with the fly does not strongly select for either postinfestation resistance or tolerance of parasitoid larvae in male crickets.
在昆虫寄生虫中，内寄生蜂对宿主的防御构成了代价高昂的挑战，因为它们利用宿主的身体来发育和成熟自己的卵或幼虫，最终杀死宿主。寄蝇是高度特化的、通过声音定向的寄生蜂，其初孵幼虫可移动，会钻入宿主体内取食。我们研究了田野蟋蟀在被寄生蝇幼虫感染后是否会采取感染后策略以最大限度地提高存活率。我们使用来自考艾岛（该寄生蜂存在）和库克群岛（曼加伊亚，该寄生蜂不存在）的蟋蟀，通过比较实验感染幼虫的雄性蟋蟀的取食行为、繁殖能力和存活率，评估了感染的适应性后果。我们还通过比较不同时间感染蝇幼虫的蟋蟀与未感染对照蟋蟀的基因表达，评估了宿主反应的潜在机制。我们观察到在适应性（精包产生）和存活率（感染后总存活时间）方面存在微弱的种群差异。这些反应通常未显示种群与携带的幼虫宿主数量或宿主身体状况之间的相互作用。基因表达模式也揭示了对感染反应的种群差异，但我们没有发现与免疫或应激反应相关基因存在一致差异的证据。一种可能性是，任何感染后进化出的抗性并不涉及与这些特定功能类别相关的基因。更有可能的是，这些结果表明与寄蝇的共同进化并没有强烈地选择雄性蟋蟀对感染后抗性或对寄生蜂幼虫的耐受性。
