Perrot-Minnot Marie-Jeanne, Sanchez-Thirion Kevin, Cézilly Frank
Université de Bourgogne, UMR CNRS 6282 Biogéosciences, Dijon, France
Université de Bourgogne, UMR CNRS 6282 Biogéosciences, Dijon, France.
Proc Biol Sci. 2014 Dec 7;281(1796):20141915. doi: 10.1098/rspb.2014.1915.
Manipulative parasites often alter the phenotype of their hosts along multiple dimensions. 'Multidimensionality' in host manipulation could consist in the simultaneous alteration of several physiological pathways independently of one another, or proceed from the disruption of some key physiological parameter, followed by a cascade of effects. We compared multidimensionality in 'host manipulation' between two closely related amphipods, Gammarus fossarum and Gammarus pulex, naturally and experimentally infected with Pomphorhynchus laevis (Acanthocephala), respectively. To that end, we calculated in each host-parasite association the effect size of the difference between infected and uninfected individuals for six different traits (activity, phototaxis, geotaxis, attraction to conspecifics, refuge use and metabolic rate). The effects sizes were highly correlated between host-parasite associations, providing evidence for a relatively constant 'infection syndrome'. Using the same methodology, we compared the extent of phenotypic alterations induced by an experimental injection of serotonin (5-HT) in uninfected G. pulex to that induced by experimental or natural infection with P. laevis. We observed a significant correlation between effect sizes across the six traits, indicating that injection with 5-HT can faithfully mimic the 'infection syndrome'. This is, to our knowledge, the first experimental evidence that multidimensionality in host manipulation can proceed, at least partly, from the disruption of some major physiological mechanism.
操纵性寄生虫常常会在多个维度上改变宿主的表型。宿主操纵中的“多维度性”可能包括同时独立改变多个生理途径，或者源于某些关键生理参数的破坏，随后引发一系列效应。我们比较了两种亲缘关系密切的双足类动物——分别自然感染和实验感染了平滑棘头虫（棘头虫纲）的溪钩虾和蚤状钩虾——在“宿主操纵”方面的多维度性。为此，我们在每种宿主 - 寄生虫组合中，计算了感染个体和未感染个体在六个不同性状（活动、趋光性、趋地性、对同种个体的吸引力、避难所使用和代谢率）上差异的效应大小。宿主 - 寄生虫组合之间的效应大小高度相关，这为相对恒定的“感染综合征”提供了证据。使用相同的方法，我们比较了在未感染的蚤状钩虾中通过实验注射血清素（5 - HT）所诱导的表型改变程度，与通过平滑棘头虫实验感染或自然感染所诱导的表型改变程度。我们观察到六个性状的效应大小之间存在显著相关性，表明注射5 - HT能够忠实地模拟“感染综合征”。据我们所知，这是首个实验证据，表明宿主操纵中的多维度性至少部分可能源于某些主要生理机制的破坏。
