Shikano Ikkei, Cory Jenny S
Department of Biological Sciences, Simon Fraser University, Burnaby, BC V5A1S6, Canada.
Department of Biological Sciences, Simon Fraser University, Burnaby, BC V5A1S6, Canada.
J Invertebr Pathol. 2016 Sep;139:25-33. doi: 10.1016/j.jip.2016.07.005. Epub 2016 Jul 11.
Infection by parasites can alter the feeding behaviour of hosts. Some animals seek out substances that can therapeutically clear infections (self-medication), some may seek out resources to recoup resources lost while fighting off infection (compensatory feeding) and others may be manipulated to ingest substances that benefit parasite fitness (parasite manipulation of host). Recent studies have indicated that pathogen-challenged insects can self-medicate by increasing their protein intake relative to carbohydrate, which is thought to act by boosting the insect's immune response. However, increased protein intake could also be due to compensatory feeding or pathogen manipulation of the host, and a rigorous examination of all four of the testable predictions, which is necessary for verifying self-medication behaviour, has not been conducted. The therapeutic behaviour must (1) only be employed by infected individuals and (2) alleviate the potential fitness loss of the infected individual. (3) If an uninfected individual engages in the behaviour, they suffer a decrease in fitness, and lastly, (4) the parasite cannot benefit from the behaviour. In response to baculovirus-challenge (AcMNPV) at 24°C, the cabbage looper, Trichoplusia ni, increased proportional protein intake, by increasing protein intake rather than decreasing carbohydrate intake. Increased protein intake did not benefit virus fitness, but it also did not increase the probability of host survival. Increased proportional protein intake did not occur in response to TnSNPV-challenge at 24°C or in response to AcMNPV-challenge at a higher temperature (32°C), indicating that the virus-induced change in nutrient intake depends on virus identity and temperature. Since virus-challenged T. ni did not show the typical costs associated with infection, the altered nutrient intake is likely to be a compensatory response. Understanding the motivation behind pathogen-induced changes in feeding behaviour could have significant implications for determining its importance for species interactions at multiple trophic levels.
寄生虫感染会改变宿主的摄食行为。一些动物会寻找能够治疗性清除感染的物质（自我药疗），一些动物可能会寻找资源来弥补在抵抗感染过程中损失的资源（补偿性摄食），还有一些动物可能会被操控去摄取有利于寄生虫健康的物质（寄生虫对宿主的操控）。最近的研究表明，受到病原体挑战的昆虫会通过相对于碳水化合物增加蛋白质摄入量来进行自我药疗，这被认为是通过增强昆虫的免疫反应来发挥作用。然而，蛋白质摄入量的增加也可能是由于补偿性摄食或病原体对宿主的操控，并且尚未对所有四个可测试的预测进行严格检验，而这对于验证自我药疗行为是必要的。这种治疗行为必须（1）仅由受感染个体采用，并且（2）减轻受感染个体潜在的健康损失。（3）如果未受感染的个体进行这种行为，它们的健康会下降，最后，（4）寄生虫无法从这种行为中获益。在24°C下受到杆状病毒（AcMNPV）挑战时，甘蓝夜蛾（Trichoplusia ni）通过增加蛋白质摄入量而非减少碳水化合物摄入量来增加蛋白质摄入比例。蛋白质摄入量的增加对病毒健康没有益处，但也没有增加宿主存活的概率。在24°C下受到TnSNPV挑战或在更高温度（32°C）下受到AcMNPV挑战时，并没有出现蛋白质摄入比例增加的情况，这表明病毒诱导的营养摄入变化取决于病毒种类和温度。由于受到病毒挑战的甘蓝夜蛾没有表现出与感染相关的典型代价，营养摄入的改变很可能是一种补偿反应。了解病原体诱导的摄食行为变化背后的动机，对于确定其在多个营养级的物种相互作用中的重要性可能具有重大意义。
