Morris Alex, Green Michael, Martin Hayley, Crossland Katie, Swaney William T, Williamson Sally M, Rae Robbie
Liverpool John Moores University, School of Natural Sciences and Psychology, Byrom Street, L33AF, United Kingdom.
Liverpool John Moores University, School of Natural Sciences and Psychology, Byrom Street, L33AF, United Kingdom.
Behav Processes. 2018 Jun;151:73-80. doi: 10.1016/j.beproc.2018.02.021. Epub 2018 Feb 27.
The ability of parasites to manipulate the behaviour of their hosts has evolved multiple times, and has a clear fitness benefit to the parasite in terms of facilitating growth, reproduction and transfer to suitable hosts. The mechanisms by which these behavioural changes are induced are poorly understood, but in many cases parasite manipulation of serotonergic signalling in the host brain is implicated. Here we report that Phasmarhabditis hermaphrodita, a parasite of terrestrial gastropod molluscs, can alter the behaviour of slugs. Uninfected slugs (Deroceras panormitanum, Arion subfuscus and Arion hortensis) avoid areas where P. hermaphrodita is present, but slugs infected with P. hermaphrodita are more likely to be found where the nematodes are present. This ability is specific to P. hermaphrodita and other nematodes (Steinernema carpocapsae and Heterorhabditis bacteriophora) do not induce this behavioural change. To investigate how P. hermaphrodita changes slug behaviour we exposed slugs to fluoxetine (a selective serotonin reuptake inhibitor) and cyproheptadine (a serotonin receptor antagonist). Uninfected slugs fed fluoxetine no longer avoided areas where P. hermaphrodita was present; and conversely, infected slugs fed cyproheptadine showed no increased attraction to areas with nematodes. These findings suggest that a possible mechanism by which P. hermaphrodita is able to manipulate parasite avoidance behaviour in host slugs is by manipulating serotonergic signalling in the brain, and that increased serotonin levels are potentially associated with a reduction in parasite avoidance.
寄生虫操纵宿主行为的能力已经多次进化，就促进其生长、繁殖以及转移到合适的宿主而言，这对寄生虫具有明显的适应性益处。这些行为变化是如何被诱导的机制尚不清楚，但在许多情况下，寄生虫对宿主大脑中血清素信号传导的操纵被认为与此有关。在此我们报告，陆生腹足纲软体动物的寄生虫——雌雄同体细线虫（Phasmarhabditis hermaphrodita）能够改变蛞蝓的行为。未感染的蛞蝓（泛全环蛞蝓（Deroceras panormitanum）、暗褐蛞蝓（Arion subfuscus）和庭园蛞蝓（Arion hortensis））会避开存在雌雄同体细线虫的区域，但感染了雌雄同体细线虫的蛞蝓更有可能出现在有线虫的地方。这种能力是雌雄同体细线虫所特有的，其他线虫（小卷蛾斯氏线虫（Steinernema carpocapsae）和嗜菌异小杆线虫（Heterorhabditis bacteriophora））不会诱导这种行为变化。为了研究雌雄同体细线虫如何改变蛞蝓行为，我们让蛞蝓接触氟西汀（一种选择性5-羟色胺再摄取抑制剂）和赛庚啶（一种5-羟色胺受体拮抗剂）。喂食氟西汀的未感染蛞蝓不再避开存在雌雄同体细线虫的区域；相反，喂食赛庚啶的感染蛞蝓对有线虫区域没有表现出更强的吸引力。这些发现表明，雌雄同体细线虫能够操纵宿主蛞蝓的寄生虫回避行为的一种可能机制是通过操纵大脑中的血清素信号传导，并且血清素水平升高可能与寄生虫回避行为的减少有关。
