Varaldi J, Petit S, Boulétreau M, Fleury F
Laboratoire de Biométrie et Biologie Evolutive, UMR 5558, CNRS, Univ. Lyon 1, 43 bd 11 nov, 69622, Villeubanne Cedex, France.
Parasitology. 2006 Jun;132(Pt 6):747-56. doi: 10.1017/S0031182006009930.
Parasites often induce behavioural changes in their host. However, it is not necessarily easy to determine whether these changes are representative of an adaptation of the parasite (parasite manipulation), an adaptive response of the host or a side-effect of infection. In a solitary parasitoid of Drosophila larvae (Leptopilina boulardi), viral particles (LbFV) modify the host acceptance behaviour of infected females by increasing their tendency to superparasitize. This behavioural alteration allows for the horizontal transmission of the virus within superparasitized Drosophila larvae. To add support for or against the 'manipulation hypothesis', we investigated whether other behavioural components of the parasitoid are affected by viral infection, and whether other forms of horizontal transmission exist. Neither the ability of females to locate host kairomones nor their daily rhythm of locomotor activity was affected by viral infection. However, infected females showed a lower rate of locomotor activity, suggesting a physiological cost of infection. The searching paths of females were also unaffected. Males from infected and uninfected lines showed the same ability to locate females'sexual pheromones. Moreover, alternative modes of horizontal transmission (through food consumption and/or contact with the same Drosophila larvae) did not lead to viral contamination of the parasitoid. The overall specificity of behavioural alteration and of viral horizontal transmission is consistent with the hypothesis that the virus manipulates the behaviour of the parasitoid.
寄生虫常常会诱导其宿主的行为发生变化。然而，要确定这些变化是代表寄生虫的一种适应性表现（寄生虫操控）、宿主的适应性反应还是感染的副作用，并非总是易事。在一种果蝇幼虫的独居寄生蜂（布氏潜蝇茧蜂）中，病毒颗粒（LbFV）通过增加其过度寄生的倾向，改变了受感染雌蜂的宿主接受行为。这种行为改变使得病毒能在被过度寄生的果蝇幼虫中进行水平传播。为了支持或反对“操控假说”，我们研究了病毒感染是否会影响寄生蜂的其他行为成分，以及是否存在其他形式的水平传播。病毒感染既不影响雌蜂定位宿主信息素的能力，也不影响其日常运动活动节律。然而，受感染的雌蜂表现出较低的运动活动速率，这表明感染存在生理代价。雌蜂的搜索路径也未受影响。来自受感染和未受感染品系的雄蜂在定位雌蜂性信息素方面表现出相同的能力。此外，水平传播的替代模式（通过食物摄取和/或与相同的果蝇幼虫接触）并未导致寄生蜂被病毒污染。行为改变和病毒水平传播的总体特异性与病毒操控寄生蜂行为的假说相符。
