Analysis of acquirement mechanism for nutritional resource in host-parasitoid interaction

寄主和寄生虫之间建立的营养关系从来都不是简单的，往往反映出彼此之间长期的共同进化“军备竞赛”。在这场军备竞赛中，宿主进化出一种机制，使它们能够逃离或消灭寄生虫；另一方面，寄生虫需要克服宿主的防御，并将宿主用作营养库。寄生蜂幼虫选择性地以某些寄主组织为食，以保持对寄主的最小伤害。寄主在发育早期受到严重破坏，可能导致寄生蜂的早熟死亡。仅以营养丰富的血淋巴为食是寄生蜂的一种策略。幼虫被用来将对宿主的损害降到最低。血淋巴具有很高的营养价值，因为它通过一种特殊的代谢途径，通过抑制脂肪体对营养的吸收，或仅通过缓慢减少脂肪体的量，有效地提取已经或即将储存在脂肪体等器官中的营养。然而，眼镜蛇幼虫拥有发育良好的肠道，可以在后期消化一些食物。此外，在幼虫后期，寄生蜂幼虫在化蛹前表现出快速生长。这些事实很难单凭宿主血淋巴的营养吸收来解释。阐明外寄生和内寄生的无核生物是如何利用寄主作为食物来源的，这将有助于阐明无核生物共同或不同策略的进化。我们研究了使寄生蜂能够确保外寄生和内寄生的无核幼虫都有足够的食物资源的策略，并解释了寄生幼虫如何利用寄主资源来提高成功的寄生。

The nutritional relationship that is established between hosts and their parasites is never simple and often reflects a long co-evolutionary ‘arms-race' between each other. In this arms-race, hosts evolve mechanisms that enable them to escape from their parasites or to eliminate them ; on the other hand, the parasites need to overcome host defenses and utilize the host as a nutritional reservoir. The parasitoid larvae feed selectively on certain host tissues in order to keep a minimal damage to the host. Severe damage of the host during early development may lead to precocious death of the parasitoid. Feeding exclusively on the nutrient-rich hemolymph is one strategy that parasitoid. larvae employed to minimize host damage. Hemolymph retains a high nutritional value since it efficiently retrieves nutrients, which have already been or are to be stored in organs like the fat body via a specialized metabolic pathway, through inhibition of absorption of nutrients by the fat body, or only by slowly reducing the amount of fat body. The koinobiont larvae, however, possess well-developed gut to digest some foods during their late stages. Also, during late larval stages, the parasitoid larvae exhibit rapid growth just prior to pupation. These facts are difficult to explain on the sole basis of nutrient uptake from host hemolymph. Elucidation of how ecto- and endo-parasitic koinobionts utilize the hosts as a food resource will be useful in clarifying the evolution of common or different strategies in koinobionts. We studied strategies that enable parasitoids to ensure a sufficient food resource in both ecto- and endoparasitic koinobionts and explain how the parasitoid larvae utilize the host resource to enhance successful parasitism.