Data from: Increased behavioural lateralization in parasitized coral reef fish

Preferential use of one side of the body for cognitive or behavioural tasks (lateralization) is common in many animals, including humans. However, few studies have demonstrated whether lateralization is phenotypically plastic, and varies depending on the ecological context. We studied lateralization (measured as a turning preference) in the bridled monocle bream (Scolopsis bilineatus). This coral reef fish is commonly infected by a large, ectoparasitic isopod (Anilocra nemipteri) that attaches to the left or right side of its host's head. Fish that were parasitized showed no turning bias with respect to the side on which the parasite had attached. On average, however, parasitised fish were significantly more lateralized (i.e. had a strong side bias) than unparasitized fish. The extent of lateralization declined significantly when we experimentally removed the parasite. Our results indicate that lateralization can vary with the ecological context. One possible explanation is that lateralization shortens the response time until fish flee after encountering a predator. A stronger side bias might be advantageous for parasitized individuals to overcome their recently documented lower maximum swimming speed.

身体单侧在认知或行为任务中的偏好性使用（偏侧化，lateralization）在包括人类在内的众多动物中均普遍存在。然而，目前鲜有研究证实偏侧化是否具备表型可塑性，且会随生态情境发生变化。我们以带纹眶棘鲈（Scolopsis bilineatus）为研究对象，对其偏侧化（以转向偏好为衡量指标）展开了研究。该珊瑚礁鱼类常会被一种大型外寄生等足类动物（Anilocra nemipteri）感染，这类寄生虫会附着在宿主头部的左侧或右侧。被寄生的个体并未表现出与寄生虫附着侧相关的转向偏倚。但平均而言，被寄生个体的偏侧化程度显著高于未被寄生个体——即前者呈现出更强的单侧偏好。当我们通过实验移除寄生虫后，个体的偏侧化程度出现了显著下降。本研究结果表明，偏侧化可随生态情境发生动态变化。一种可能的解释是，偏侧化能够缩短鱼类遭遇捕食者后的逃逸反应时长。对于被寄生个体而言，更强的单侧偏好或许有助于弥补此前已有研究记录的较低最大游泳速度劣势。