Kuramitsu Kazumu, Kainoh Yooichi, Konno Kotaro
Faculty of Life and Environmental Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki, 305-8572, Japan.
Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), 1‑2 Owashi, Tsukuba, Ibaraki, 305‑8634, Japan.
Sci Rep. 2025 Mar 11;15(1):8361. doi: 10.1038/s41598-025-91403-3.
Parasitoid wasps serve as natural enemies of numerous insect species; therefore, knowledge of host-parasitoid interactions is fundamental for understanding ecosystems. Each endoparasitoid wasp taxon exhibits a specific host range. Female parasitoids, however, occasionally oviposit into non-host species. Since the survival probability of eggs in non-host species is virtually zero, these behaviors have long been considered maladaptive. However, in the present study, we found that eggs of a specialist parasitoid, Cotesia kariyai (Hymenoptera: Braconidae), oviposited in unsuitable host caterpillars, Mythimna loreyi (Lepidoptera: Noctuidae), successfully complete larval development in the non-host when these caterpillars are simultaneously oviposited by another naturally sympatric parasitoid wasp, Meteorus pulchricornis (Hymenoptera: Braconidae), for which My. loreyi is the usual host. This observation suggests that the seemingly maladaptive behavior of ovipositing in unsuitable host insects can be adaptive, allowing them to maintain reproductive potential in environments where their ordinary hosts are absent. We propose a new term, "pirate parasitism", for this type of obligatory multiparasitism. Understanding detailed mechanisms of this phenomenon may provide deeper insights into parasitoid-host dynamics and evolution of host use strategies by parasitoids.
寄生蜂是众多昆虫物种的天敌；因此，了解寄主与寄生蜂之间的相互作用是理解生态系统的基础。每种内寄生蜂类群都有特定的寄主范围。然而，雌性寄生蜂偶尔会将卵产在非寄主物种体内。由于卵在非寄主物种中的存活概率几乎为零，这些行为长期以来一直被认为是适应不良的。然而，在本研究中，我们发现一种专性寄生蜂——狩野小腹茧蜂（膜翅目：茧蜂科）——产在不合适的寄主毛虫——劳氏粘虫（鳞翅目：夜蛾科）——体内的卵，当这些毛虫同时被另一种自然同域分布的寄生蜂——美丽流星茧蜂（膜翅目：茧蜂科）——产卵时（劳氏粘虫是美丽流星茧蜂的常见寄主），能在非寄主体内成功完成幼虫发育。这一观察结果表明，在不合适的寄主昆虫体内产卵这种看似适应不良的行为可能是适应性的，使它们能够在缺少其正常寄主的环境中维持繁殖潜力。我们为这种类型的 obligatory multiparasitism 提出了一个新术语——“海盗寄生”。了解这一现象的详细机制可能会为寄生蜂 - 寄主动态以及寄生蜂寄主利用策略的进化提供更深入的见解。
