内寄生蜂幼虫于寄主体外取食行为的适应性研究

Host selection, development and reproductive strategies in parasitoids insects are essential topic of parasitoids behavioral ecology. They are correlated with the optimal fitness of parasitoids directly, and then, have an impact on population dynamics between parasitoids and hosts. A number of hypothesis and theories about host selection, development and reproductive strategies have been developed. However, almost all of these hypothesis or theories were proposed basing on the developmental models that the parasitoids larvae feeding within the host bodies fully and egressed outside without subsequent host feeding behavior. According to our investigation, Aulacococentrum Confusum, which is endoparasitoids, exhibit a particular behavior that they continue to feeding on hosts after egression. In the present study, we will use Aulacococentrum Confusum and Glyphodes pyloalis as the model system to study the effect of post-egressed host feeding behavior on the host selection, development and reproductive strategy of A. Confusum, furthermore, we will explore whether this host feeding behavior is adaptive for the female wasps to avoid mortality risk. Fully understandings of this particular parasitism model of post-egression host feeding behavior would be expected. Therefore, it is believed that novel knowledge, essential mechanism and parameters would be obtained and classical hypothesis or theories of parasitoids behavioral ecology would be enriched. Meanwhile, our research could provide reference for biological control on the pests of mulberry trees.

寄生蜂是行为生态学研究的理想模式生物，其寄主选择、发育和繁殖特征在其生活史进化中形成了适合度最大化的策略。长期以来，针对寄主选择及发育和繁殖策略提出了一系列假说或理论，但这些假说或理论都基于寄生蜂幼虫爬出寄主后不再取食寄主的寄生模式。我们在前期调查中发现，内寄生性混腔室茧蜂表现出幼虫钻出寄主桑螟幼虫体壁后继续取食寄主的特殊行为，属于一种新的寄生模式。为揭示该寄生模式的适应意义，本研究以混腔室茧蜂—桑螟为寄生蜂—寄主模式生物，运用行为生态学理论和方法，观察幼虫体外取食寄主行为对混腔室茧蜂寄主选择行为、子代发育和繁殖特性的影响，探究其生活史策略以及体外取食对规避死亡风险的影响。预期将阐释内寄生性寄生蜂幼虫体外取食寄主这种特殊行为的适应性意义。本研究成果将获得关于寄生蜂寄生行为的新知识、重要的机理和参数，从而丰富和完善经典的寄生蜂行为生态学理论，同时也为生物防治桑树螟虫提供参考。

混腔室茧蜂是桑树重大害虫桑螟的优势容性内寄生蜂，其幼虫具有钻出寄主体壁后继续取食寄主的特殊行为，属于一种新的寄生模式。本项目研究了继续取食行为的特征及其适应性，并探究了该寄生蜂的寄主选择行为策略及其与寄主的互作关系。结果表明，继续取食行为历时约5.5h，取食完毕后仅剩寄主头壳。如缺乏该行为，子代蜂蛹重、体型大小等适合度指标均显著下降。寄生蜂诱导寄主建造丝状结构更为致密的蛹室，并利用该蛹室有效规避捕食风险；寄生蜂寄生2至5龄桑螟时，产出子代数量未表现显著差异，表明寄生蜂不依赖寄主龄期做出寄主选择决策，但中间龄期寄主产出的子代显著偏雌性。卵-蛹发育时间随寄主龄期增加而缩短，蛹-成虫发育时间受寄主龄期和子代性别影响显著。雌性子代体型显著大于雄性。子代寿命不受寄生时寄主龄期和子代性别影响。随着寄生蜂日龄的增加，寄生数显著上升；寄生蜂幼虫在寄主体内取食阶段，寄主体质量及血淋巴中总糖、海藻糖和蛋白质的含量均未发生显著变化，但蜕皮激素和保幼激素浓度显著上升，表明混腔室茧蜂能够调控寄主内分泌系统；构建了桑螟响应寄生蜂寄生的差异转录组，共发现有2327个基因发生差异表达，并从中鉴定了96个免疫相关基因，选取10个差异表达基因进行了qRT-PCR验证，为后续深入研究寄生蜂与寄主的互作关系提供了重要依据；鉴定了14个桑螟热激蛋白基因，qRT-PCR结果表明这些基因在寄生后不同时间点差异表达，表明它们可能参与了桑螟响应寄生的生理反应；鉴定了混腔室茧蜂触角的感器类型并筛选验证了12个气味结合蛋白基因，为进行寄生蜂行为生态学的分子机制研究提供了重要参考。本研究获得的结果基本明确了容性内寄生蜂幼虫体外取食行为的特征及其适应性，阐明了该类型寄生蜂寄主选择策略及其对寄主发育和营养的调控机制，从而丰富了对容性内寄生蜂发育模式的认识，也为深入研究桑树害虫寄生蜂提供了重要参考。此外，本项目还研究了寄生蜂的嗅觉基因及糖分营养对寄生蜂生活史特征的影响。