Data from: Learned parasite avoidance is driven by host personality and resistance to infection in a fish-trematode interaction

Cognitive abilities related to the assessment of risk improve survival. While earlier studies have examined the ability of animals to learn avoiding predators, learned parasite avoidance has received little interest. In a series of behavioural trials with the trematode parasite Diplostomum pseudospathaceum, we asked whether sea trout (Salmo trutta trutta) hosts show associative learning in the context of parasitism and if so, whether learning capacity is related to the likelihood of infection mediated through host personality and resistance. We show that animals are capable of learning to avoid visual cues associated with the presence of parasites. However, avoidance behaviour ceased after the likely activation of host resistance following consecutive exposures during learning, suggesting that resistance to infection outweighs avoidance. Further, we found a positive relationship between learning ability and boldness, suggesting a compensation of risky life-styles through increased investment in cognitive abilities. In contrast, an increased risk of infection due to low resistance was not balanced by learning ability. Instead, these traits were positively related, which may be explained by inherent physiological qualities controlling both traits. Overall, the results demonstrate that parasitism, in addition to other biological interactions such as predation, is an important selective factor in the evolution of animal cognition.

与风险评估相关的认知能力可提升生存几率。既往研究多聚焦于动物习得躲避捕食者的能力，而对习得性寄生虫规避行为的关注却相对匮乏。本研究以复殖吸虫（trematode parasite）Diplostomum pseudospathaceum为研究对象，通过一系列行为学实验，探究海鳟（Salmo trutta trutta）宿主是否会在寄生情境下产生联想学习（associative learning）；若存在该学习能力，其学习能力是否与宿主个性、抗性介导的感染风险存在关联。研究结果表明，动物能够学会规避与寄生虫存在相关联的视觉线索。然而，在实验过程中经连续暴露后，宿主的感染抗性被激活，规避行为随即消失，这提示感染抗性的作用强度高于行为规避。进一步分析显示，学习能力与大胆特质（boldness）呈正相关，提示个体可通过提升认知资源投入，代偿其高风险的生活策略。与之相反，因宿主抗性低下导致的感染风险升高，并未通过提升学习能力得到补偿；反而二者呈显著正相关，这一现象可通过同时调控这两种性状的内在生理特性加以解释。综上，相较于捕食等其他生物交互作用，寄生作用是推动动物认知演化的重要选择压力之一。