University of Regensburg, Institute for Zoology, Universitätsstraße 31, 93053, Regensburg, Germany.
J Chem Ecol. 2012 Apr;38(4):331-9. doi: 10.1007/s10886-012-0103-0. Epub 2012 Apr 5.
Chemical defense mechanisms are widespread among insects but have rarely been demonstrated in parasitoid wasps. Here, we show that the Drosophila parasitoid Leptopilina heterotoma (Hymenoptera, Figitidae) produces (-)-iridomyrmecin and (+)-isoiridomyrmecin in a cephalic gland, and that these chemicals have a highly repellent effect on ants. Stereoselective synthesis of 4 stereoisomers of iridomyrmecin allowed us to demonstrate that the repellent effect of iridomyrmecins depends on the stereochemistry. Potential food items impregnated with natural doses of (-)-iridomyrmecin were avoided by ants much longer than those impregnated with (+)-iridomyrmecin, (+)-isoiridomyrmecin, or (-)-isoiridomyrmecin, respectively. Quantitative headspace analyses revealed furthermore that females and males of L. heterotoma released iridomyrmecins in higher amounts when confronted with ants. This is the first time, that (-)-iridomyrmecin and (+)-isoiridomyrmecin are reported as natural products. Females synthesize more iridomyrmecins than males, and the most active (-)-iridomyrmecin is produced by females only. We, therefore, hypothesize that this defense mechanism is used mainly by female wasps when foraging for Drosophila larvae on rotten fruits, but also may protect male wasps during dispersal.
昆虫体内广泛存在化学防御机制，但在寄生性胡蜂中却很少见。在这里，我们发现黑腹果蝇的寄生蜂长柄胡蜂（膜翅目，姬蜂科）在头部腺体中产生 (-)-iridomyrmecin 和 (+)-isoiridomyrmecin，并且这些化学物质对蚂蚁具有很强的驱避作用。4 种立体异构体的立体选择性合成使我们能够证明 iridomyrmecin 的驱避作用取决于立体化学。用天然剂量的 (-)-iridomyrmecin 浸渍的潜在食物比 (+)-iridomyrmecin、(+)-isoiridomyrmecin 或 (-)-isoiridomyrmecin 浸渍的食物更能长时间被蚂蚁避免。此外，定量顶空分析还表明，当面临蚂蚁时，L. heterotoma 的雌性和雄性释放出更多的 iridomyrmecin。这是首次报道 (-)-iridomyrmecin 和 (+)-isoiridomyrmecin 是天然产物。雌性合成的 iridomyrmecin 多于雄性，并且最活跃的 (-)-iridomyrmecin 仅由雌性产生。因此，我们假设这种防御机制主要由雌性胡蜂在腐烂的水果上寻找果蝇幼虫时使用，但也可能在雄性胡蜂扩散期间保护它们。
