Institut de Recherche sur la Biologie de l'Insecte, UMR 6035 CNRS, Université François Rabelais, 37200, Tours, France.
J Chem Ecol. 2010 May;36(5):513-21. doi: 10.1007/s10886-010-9781-7. Epub 2010 Apr 13.
In solitary parasitoids, only one adult can emerge from a given host. In some of these species, when several eggs are laid on the same host, supernumerary individuals are eliminated by lethal larval fights. In the solitary parasitoid Anisopteromalus calandrae, the probability of a second larva winning the fight depends on the time elapsed since the first oviposition. The older the first egg is at the moment a second egg is laid, the less chance the second egg has of winning the competition. As a consequence, females of this species lay their eggs preferentially on recently parasitized hosts rather than on hosts parasitized by an egg about to hatch. Anisopteromalus calandrae females parasitize bruchid larvae located in cowpea seeds. In a series of choice test experiments using an artificial seed system, we demonstrated that the cue that allows parasitoid females to differentiate between hosts parasitized for different lengths of time comes from the host and not from the artificial seed or the previously laid egg. This cue is perceived at short range, indicating that the chemicals involved are probably partly volatile. Interestingly, although parasitism stops host development, cuticular profiles continue to evolve, but in a different way from those of unparasitized hosts. This difference in the host's cuticular profile after parasitism, therefore, probably underlies the parasitoid female's discrimination.
在单寄生蜂中，每个宿主只能孵化出一个成虫。在这些物种中的一些中，当多个卵被产在同一个宿主上时，多余的个体通过致命的幼虫战斗被淘汰。在单寄生蜂暗褐臀沟茧蜂中，第二个幼虫赢得战斗的概率取决于第一个卵产下后经过的时间。第一个卵产得越早，第二个卵获胜的机会就越小。因此，这种物种的雌性会优先在最近被寄生的宿主上产卵，而不是在即将孵化的宿主上产卵。暗褐臀沟茧蜂的雌性寄生在豇豆种子中的豆象幼虫上。在一系列使用人工种子系统的选择测试实验中，我们证明了允许寄生蜂雌区分已被寄生不同时间的宿主的线索来自宿主，而不是来自人工种子或先前产的卵。这个线索在短距离内被感知，表明涉及的化学物质可能部分是挥发性的。有趣的是，尽管寄生会阻止宿主的发育，但表皮轮廓继续演变，但与未被寄生的宿主的方式不同。因此，寄生后宿主表皮轮廓的这种差异可能是寄生蜂雌蜂区分的基础。
