Harvey Jeffrey A, Fei Minghui, Lammers Mark, Kos Martine, Zhu Feng, Heinen Robin, Poelman Erik H, Gols Rieta
Department of Terrestrial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Droevendaalsesteeg 10, 6708 PB Wageningen, The Netherlands; Vrije Universeteit Amsterdam, Department of Ecological Sciences, Section Animal Ecology, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands.
Department of Terrestrial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Droevendaalsesteeg 10, 6708 PB Wageningen, The Netherlands.
J Insect Physiol. 2016 Jul;90:36-42. doi: 10.1016/j.jinsphys.2016.05.006. Epub 2016 May 30.
Parasitoid wasps are excellent organisms for studying the allocation of host resources to different fitness functions such as adult body mass and development time. Koinobiont parasitoids attack hosts that continue feeding and growing during parasitism, whereas idiobiont parasitoids attack non-growing host stages or paralyzed hosts. Many adult female koinobionts attack a broad range of host stages and are therefore faced with a different set of dynamic challenges compared with idiobionts, where host resources are largely static. Thus far studies on solitary koinobionts have been almost exclusively based on primary parasitoids, yet it is known that many of these are in turn attacked by both koinobiont and idiobiont hyperparasitoids. Here we compare parasitism and development of a primary koinobiont hyperparasitoid, Mesochorus gemellus (Hymenoptera: Ichneumonidae) in larvae of the gregarious primary koinobiont parasitoid, Cotesia glomerata (Hymenoptera: Braconidae) developing in the secondary herbivore host, Pieris brassicae (Lepidoptera: Pieridae). As far as we know this is the first study to examine development of a solitary primary hyperparasitoid in different stages of its secondary herbivore host. Pieris brassicae caterpillars were parasitized as L1 by C. glomerata and then these parasitized caterpillars were presented in separate cohorts to M. gemellus as L3, L4 or L5 instar P. brassicae. Different instars of the secondary hosts were used as proxies for different developmental stages of the primary host, C. glomerata. Larvae of C. glomerata in L5 P. brassicae were significantly longer than those in L3 and L4 caterpillars. Irrespective of secondary host instar, every parasitoid cluster was hyperparasitized by M. gemellus but all only produced male progeny. Male development time decreased with host stage attacked, whereas adult male body mass did not, which shows that M. gemellus is able to optimally exploit older host larvae in terms of adult size despite their decreasing mass during the pupal stage. Across a range of cocoon masses, hyperparasitoid adult male body mass was approximately 84% as large as primary parasitoids, revealing that M. gemellus is almost as efficient at exploiting host resources as secondary (pupal) hyperparasitoids.
寄生蜂是研究宿主资源如何分配到不同适合度功能（如成虫体重和发育时间）的优良生物。共寄生性寄生蜂攻击在寄生过程中仍继续取食和生长的宿主，而异寄生性寄生蜂则攻击不生长的宿主阶段或麻痹的宿主。许多成年雌性共寄生蜂会攻击广泛的宿主阶段，因此与宿主资源基本静态的异寄生蜂相比，它们面临着一系列不同的动态挑战。到目前为止，关于独居共寄生蜂的研究几乎完全基于初级寄生蜂，但众所周知，其中许多初级寄生蜂又会受到共寄生性和异寄生性重寄生蜂的攻击。在这里，我们比较了初级共寄生性重寄生蜂双斑中啮小蜂（膜翅目：姬蜂科）在群居性初级共寄生蜂菜蛾盘绒茧蜂（膜翅目：茧蜂科）的幼虫体内的寄生和发育情况，菜蛾盘绒茧蜂在二级食草宿主粉纹夜蛾（鳞翅目：粉蝶科）体内发育。据我们所知，这是第一项研究独居初级重寄生蜂在其二阶食草宿主不同阶段发育情况的研究。粉纹夜蛾幼虫在1龄时被菜蛾盘绒茧蜂寄生，然后将这些被寄生的幼虫按不同批次分别在粉纹夜蛾3龄、4龄或5龄时提供给双斑中啮小蜂。二级宿主的不同龄期被用作初级宿主菜蛾盘绒茧蜂不同发育阶段的替代指标。在粉纹夜蛾5龄幼虫体内的菜蛾盘绒茧蜂幼虫明显比在3龄和4龄幼虫体内的长。无论二级宿主龄期如何，每个寄生蜂群体都被双斑中啮小蜂重寄生，但所有群体只产生雄性后代。雄性发育时间随着被攻击的宿主阶段而减少，而成虫雄性体重则没有，这表明双斑中啮小蜂尽管在蛹期宿主质量下降，但在成虫大小方面能够最佳地利用较老的宿主幼虫。在一系列茧质量范围内，重寄生蜂成虫雄性体重约为初级寄生蜂的84%，这表明双斑中啮小蜂在利用宿主资源方面几乎与二级（蛹期）重寄生蜂一样高效。
