Biogéosciences, UMR 6282 CNRS, Université Bourgogne Franche-Comté, 6 Boulevard Gabriel, 21000 Dijon, France.
Parasitology. 2019 Sep;146(10):1296-1304. doi: 10.1017/S0031182019000520. Epub 2019 Jun 28.
Many trophically-transmitted parasites induce behavioural alteration in their intermediate hosts that tend to increase host vulnerability to predation. Inter-population variability in parasite-induced alterations is expected to arise from variable local opportunities for trophic transmission. Yet, this hypothesis has not been investigated so far. We addressed the issue in four populations of the fish parasite Pomphorhynchus tereticollis (Acanthocephala), using variable fish biomass density as a proxy for transmission opportunities. We found variation in the intensity of parasite-induced changes in phototaxis and refuge use among populations. Two of the populations with the lowest predator biomass exhibited the highest levels of behavioural manipulation and prevalence, as expected at low transmission opportunities. They also exhibited micro-habitat segregation between infected and uninfected gammarids in the field. In addition, infection had variable effects on two physiological defence systems, immunity and antioxidant capacity, and on total protein content. Overall, our study brings partial support to the prediction that host manipulation and prevalence should be higher at low predator biomass. Although stronger evidence should be sought by increasing population replicates, our study points to the importance of the ecological context, specifically transmission opportunities brought about by predation pressure, for the evolution of parasite manipulation in trophically-transmitted parasites.
许多营养传播寄生虫会改变其中间宿主的行为，使其更容易受到捕食者的攻击。寄生虫诱导的改变在种群间的变异性预计是由于营养传播的局部机会变化引起的。然而，到目前为止，这一假设还没有得到调查。我们在四个鱼类寄生虫 Pomphorhynchus tereticollis（棘头虫）种群中解决了这个问题，使用可变的鱼类生物量密度作为传播机会的替代物。我们发现，在种群间，趋光性和避难所使用的寄生虫诱导变化的强度存在差异。在捕食者生物量最低的两个种群中，如预期的那样，在低传播机会的情况下，行为操纵和流行率最高。它们还在野外表现出受感染和未受感染的gammarids 之间的微生境分离。此外，感染对两种生理防御系统（免疫和抗氧化能力）和总蛋白含量有不同的影响。总的来说，我们的研究为宿主操纵和流行率在低捕食者生物量时应该更高的预测提供了部分支持。尽管应该通过增加种群重复来寻求更强的证据，但我们的研究表明，生态背景，特别是捕食压力带来的传播机会，对于营养传播寄生虫中寄生虫操纵的进化非常重要。
