Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA.
Proc Biol Sci. 2012 Sep 7;279(1742):3572-6. doi: 10.1098/rspb.2012.1050. Epub 2012 Jun 20.
Egg parasitoids face unique developmental constraints. First, they have exceptionally limited resources to support themselves and their siblings through three life stages. Second, they develop within the physiological system of another species, which they modify to their own ends. We examined how these constraints affect the metabolic physiology of egg parasitism, and whether parasitoids retool their host eggshell to account for their different metabolic demands. Higher-conductance eggshells allow more oxygen to reach the developing parasitoids, but also allow more water to leave the egg. We used Manduca sexta (Lepidoptera: Sphingidae) eggs and Trichogramma (Hymenoptera: Trichogrammatidae) parasitoids from southeastern AZ, USA. Compared with unparasitized Manduca eggs, eggs parasitized by Trichogramma had lower peak metabolic rates and approximately 50 per cent lower metabolic efficiency. However, developing Trichogramma were far more efficient than typical transfer efficiencies between tropic levels (approx. 10%). Even within a few hours of parasitization, eggs containing more Trichogramma had lower per-parasitoid metabolic rates, suggesting that parasitoid larvae have mechanisms for rapidly adjusting their metabolic rates based on number of siblings. Parasitoids also appear to control the conductance of their host eggshell: their different metabolic demands were mirrored by shifts in rates of water loss.
卵寄生蜂面临独特的发育限制。首先，它们拥有异常有限的资源来支持自己和兄弟姐妹完成三个生命阶段。其次，它们在另一个物种的生理系统中发育，而这种系统会被它们改造以满足自身的需求。我们研究了这些限制因素如何影响卵寄生的代谢生理学，以及寄生蜂是否会调整宿主卵壳以适应其不同的代谢需求。较高传导率的卵壳允许更多的氧气到达发育中的寄生蜂，但也允许更多的水分离开卵。我们使用了来自美国亚利桑那州东南部的烟夜蛾（鳞翅目：夜蛾科）卵和赤眼蜂（膜翅目：赤眼蜂科）寄生蜂。与未被寄生的烟夜蛾卵相比，被赤眼蜂寄生的卵的代谢峰值较低，代谢效率约低 50%。然而，正在发育的赤眼蜂比典型的营养级间转移效率（约 10%）要高效得多。即使在被寄生后的几个小时内，卵中寄生的赤眼蜂数量越多，每个寄生蜂的代谢率越低，这表明寄生蜂幼虫具有根据兄弟姐妹数量快速调整代谢率的机制。寄生蜂似乎也在控制宿主卵壳的传导率：它们不同的代谢需求反映在水分流失率的变化上。
