Dianne Lucile, Perrot-Minnot Marie-Jeanne, Bauer Alexandre, Guvenatam Arnaud, Rigaud Thierry
Université de Bourgogne, Laboratoire Biogéosciences, UMR CNRS 6282, équipe Ecologie Evolutive, 21000 Dijon, France.
Université de Bourgogne, Laboratoire Biogéosciences, UMR CNRS 6282, équipe Ecologie Evolutive, 21000 Dijon, France.
Int J Parasitol. 2014 Mar;44(3-4):211-6. doi: 10.1016/j.ijpara.2013.11.001. Epub 2013 Dec 1.
Larvae of many trophically-transmitted parasites alter the behaviour of their intermediate host in ways that increase their probability of transmission to the next host in their life cycle. Before reaching a stage that is infective to the next host, parasite larvae may develop through several larval stages in the intermediate host that are not infective to the definitive host. Early predation at these stages results in parasite death, and it has recently been shown that non-infective larvae of some helminths decrease such risk by enhancing the anti-predator defences of the host, including decreased activity and increased sheltering. However, these behavioural changes may divert infected hosts from an optimal balance between survival and foraging (either seeking food or a mate). In this study, this hypothesis was tested using the intermediate host of the acanthocephalan parasite Pomphorhynchus laevis, the freshwater amphipod Gammarus pulex. We compared activity, refuge use, food foraging and food intake of hosts experimentally infected with the non-infective stage (acanthella), with that of uninfected gammarids. Behavioural assays were conducted in four situations varying in predation risk and in food accessibility. Acanthella-infected amphipods showed an increase in refuge use and a general reduction in activity and food intake. There was no effect of parasite intensity on these traits. Uninfected individuals showed plastic responses to water-borne cues from fish by adjusting refuge use, activity and food intake. They also foraged more when the food was placed outside the refuge. At the intra-individual level, refuge use and food intake were positively correlated in infected gammarids only. Overall, our findings suggest that uninfected gammarids exhibit risk-sensitive behaviour including increased food intake under predation risk, whereas gammarids infected with the non-infective larvae of P. laevis exhibit a lower motivation to feed, irrespective of predation risk and food accessibility.
许多经营养传播的寄生虫的幼虫会改变其中间宿主的行为，从而增加它们在生命周期中传播到下一个宿主的概率。在达到对下一个宿主具有感染性的阶段之前，寄生虫幼虫可能会在中间宿主体内经历几个对终末宿主无感染性的幼虫阶段。在这些阶段的早期被捕食会导致寄生虫死亡，最近有研究表明，一些蠕虫的非感染性幼虫通过增强宿主的反捕食防御能力来降低这种风险，包括活动减少和躲避增加。然而，这些行为变化可能会使受感染的宿主偏离生存和觅食（寻找食物或配偶）之间的最佳平衡。在本研究中，我们使用棘头虫寄生虫平滑巨吻棘头虫的中间宿主——淡水双足虾类蚤状钩虾对这一假设进行了检验。我们比较了实验感染非感染阶段（棘头蚴）的宿主与未感染的钩虾在活动、避难所使用、食物觅食和食物摄入量方面的差异。行为分析在四种捕食风险和食物可及性不同的情况下进行。感染棘头蚴的双足虾类避难所使用增加，活动和食物摄入量普遍减少。寄生虫强度对这些特征没有影响。未感染的个体通过调整避难所使用、活动和食物摄入量，对来自鱼类的水体线索表现出可塑性反应。当食物放在避难所外时，它们也会更多地觅食。在个体水平上，只有感染的钩虾避难所使用和食物摄入量呈正相关。总体而言，我们的研究结果表明，未感染的钩虾表现出风险敏感行为，包括在捕食风险下增加食物摄入量，而感染平滑巨吻棘头虫非感染性幼虫的钩虾，无论捕食风险和食物可及性如何，进食动机都较低。
