How Changes in Diet Can Enable Caterpillars to Overcome Parasite Infection

饮食的改变如何使毛毛虫克服寄生虫感染饮食行为的改变可以使个体动物治愈寄生虫感染或其他生理困扰。所有动物都有免疫防御系统，其强度可能会根据个体的饮食而改变。此外，像毛毛虫这样的食草动物可能会通过摄入和积累它们所吃植物中的有毒化学物质来杀死它们的寄生虫。本课题将研究毛熊毛虫这两种方法的抗虫行为。从以前的研究中，人们怀疑这种物种通过选择食物来抵御自然寄生虫。首先，行为实验将表征实验寄生幼虫与未寄生幼虫的饮食选择。其次，为了评估特定的饮食在抵抗寄生虫中的作用，我们将测试不同饮食对寄生和未寄生幼虫的存活率。第三，生理实验将评估这些饮食对毛虫对寄生虫的免疫反应的影响。最后，为了分析没有免疫系统的毛虫饲料对寄生虫的直接影响，将幼虫饲养在反映不同毛虫饲料的人工饲料中。新感染具有潜在致命性的寄生蝇蝇蛆（Exorista mella）的毛虫，预计会选择营养丰富的饮食来增强其免疫抵抗力。这一机制预计对毛虫的生理成本最低。然而，受到晚期寄生虫感染威胁的毛毛虫预计会选择富含天然植物毒素的饮食，称为吡咯利西啶生物碱。摄入异常大量的生物碱预计会对毛毛虫造成生理上的损失，因此被用作最后的手段。这项研究的广泛影响包括培养不同的学生和博士后，将行为、生理学和生态学与动物健康联系起来。通过公开演讲，该项目还将教育公众关于动物健康、行为和环境之间的科学联系。

Michael S. Singer, Proposal IOS-0744676How changes in diet can enable caterpillars to overcome parasite infectionChanges in feeding behavior can enable individual animals to cure themselves of parasite infections or other physiological distress. All animals have immunological defenses that can potentially change in strength based on an individual's diet. In addition, herbivores such as caterpillars may kill their parasites by ingesting and accumulating toxic chemicals found in the plants they eat. This research project will investigate these two means of anti-parasite behavior by the woolly bear caterpillar Grammia geneura. This species is suspected from previous study to ward off natural parasites through its feeding choices. First, behavioral experiments will characterize the dietary choices of experimentally parasitized caterpillars in relation to unparasitized caterpillars. Second, to evaluate the role of specific diets in resistance against parasites, the survival of parasitized and unparasitized caterpillars on different diets will be tested. Third, physiological experiments will evaluate the effects of these diets on the caterpillar's immune response to parasites. Finally, to analyze direct effects of caterpillar diet without the immune system, the parasites will be raised on artificial diets that reflect different caterpillar diets. Caterpillars newly infected by the potentially lethal, parasitic fly Exorista mella, are expected to choose a nutritious diet to enhance their immunological resistance. This mechanism is expected to carry minimal physiological costs for the caterpillar. However, caterpillars threatened by late-stage parasitic infections are expected to choose a diet rich in natural plant toxins called pyrrolizidine alkaloids. Ingesting unusually large quantities of alkaloids is expected to be physiologically costly for the caterpillar, and thus used as a last resort. The broader impacts of this research include training diverse students and a post-doctoral fellow in linking behavior, physiology, and ecology to animal health. Through public presentations, this project will also educate the public about the scientific link between animal health, behavior, and the environment.