Animals often experience changes in their environment that can be perceived as stressful. Previous evidence indicates that different individuals may have distinct stress responses. The role of serotonin (5-HT) in stress adaptation is well established, but its relationship with different defense strategies and the persistence of physiological and behavioral responses in different individuals during repeated acute stress remain unclear. In this study, using olive flounder (Paralichthys olivaceus) as a model, we analyzed the relationship between boldness and neurotransmitter 5-HT activity. We found that 5-HT suppression with 5-HT synthesis inhibitor p-chlorophenylalanine (pCPA) and 5-HT receptor subtype 1A (5-HT_1A) antagonist WAY-100635 increased their oxygen consumption rates and the boldness of shy individuals. We determined the metabolic and behavioral changes in bold and shy individuals to repeated acute stress. The results suggest that bold individuals switch on passive “energy-saving” personality by changing their defense behavior from “fight-flight” to “freeze-hide” during a threat encounter, which manifests high behavioral plasticity. Both behavioral types decreased their spontaneous activity levels, which were also strengthened by limiting metabolic rate. Interestingly, treatment with pCPA and WAY-100635 before stress procedure attenuated stress and increased the boldness across diverse behavioral types. This study provides the initial empirical evidence of how perception of stress impacts both individual defense behavior and personality in this species. These findings can enhance our comprehension of individual variability and behavioral plasticity in animals, thereby improving our ability to develop effective adaptive management strategies.

动物经常会经历环境的变化，这些变化可能会带来压力。先前的证据表明，不同的人可能有不同的压力反应。血清素（5-HT）在应激适应中的作用已得到充分证实，但其与不同防御策略的关系以及不同个体在反复急性应激期间持续的生理和行为反应仍不清楚。在本研究中，我们以牙鲆（Paralichthys olivaceus）为模型，分析了胆量与神经递质5-HT活性之间的关系。我们发现，使用 5-HT 合成抑制剂对氯苯丙氨酸 (pCPA) 和 5-HT 受体亚型 1A (5-HT _1A ) 拮抗剂 WAY-100635 抑制 5-HT 会增加害羞个体的耗氧率和胆量。我们确定了大胆和害羞的个体在反复急性压力下的代谢和行为变化。结果表明，大胆的个体在遭遇威胁时通过将防御行为从“战斗-逃跑”转变为“冻结-隐藏”来开启被动的“节能”人格，表现出​​较高的行为可塑性。这两种行为类型都会降低自发活动水平，而限制代谢率也会增强自发活动水平。有趣的是，在压力程序之前使用 pCPA 和 WAY-100635 进行治疗可以减轻压力并增加不同行为类型的勇气。这项研究提供了初步的经验证据，证明压力感知如何影响该物种的个体防御行为和性格。这些发现可以增强我们对动物个体变异性和行为可塑性的理解，从而提高我们制定有效的适应性管理策略的能力。