Data from: Food makes you a target: disentangling genetic, physiological, and behavioral effects determining susceptibility to infection

Genetics, physiology and behavior are all expected to influence the susceptibility of hosts to parasites. Furthermore, interactions between genetic and other
factors are suggested to contribute to the maintenance of genetic polymorphism in resistance when the relative susceptibility of host genotypes is context dependent. We
used a maternal sibship design and long- and short-term food deprivation treatments to test the role of family-level genetic variation, body condition, physiological
state and foraging behavior on the susceptibility of Lymnaea stagnalis snails to infection by a trematode parasite that uses chemical cues to locate its hosts. In
experimental exposures, we found that snails in the long-term food deprivation treatment contracted fewer parasites than snails that were continuously well-fed,
possibly because well-fed snails grew larger and attracted more transmission stages. When we kept the long-term feeding rates the same, but manipulated the
physiological state and foraging behavior of the snails with short-term food deprivation treatment, we found that snails that were fed before the exposure contracted
more parasites than snails that were fed during the exposure. This suggests that direct physiological effects of food processing, but not foraging behavior, predisposed
snails to infection. Feeding treatments also affected the family-level variation in snail susceptibility, suggesting that the relative susceptibility of host genotypes
was context dependent.

宿主的遗传特征、生理状态与行为模式，均会影响其对寄生虫的易感性。此外，当宿主基因型的相对易感性依赖于环境背景时，遗传与其他因素的互作被认为有助于维持抗性相关的遗传多态性。本研究采用母系半同胞实验设计（maternal sibship design），并设置长期、短期食物剥夺两种处理，以探究家系水平的遗传变异、身体状况、生理状态以及觅食行为，对静水椎实螺（Lymnaea stagnalis）被一种利用化学信号定位宿主的吸虫纲寄生虫（trematode parasite）感染的易感性的影响。在感染暴露实验中，我们发现长期食物剥夺处理组的静水椎实螺，其感染的寄生虫数量较持续饱食组更少，这可能是因为饱食个体体型更大，可吸引更多的感染阶段虫体。当我们保持长期摄食速率一致，通过短期食物剥夺处理调控螺类的生理状态与觅食行为时，我们发现暴露前摄食的个体，其感染寄生虫的数量多于暴露期间摄食的个体。这表明，是食物消化过程带来的直接生理效应，而非觅食行为，使得螺类更易被感染。摄食处理还会影响螺类易感性的家系水平变异，这也印证了宿主基因型的相对易感性确实依赖于环境背景。