秦岭细鳞鲑热生理学研究：最适、耐受及其可塑性

In the context of global warming, the adaptive evolution of species becomes a focus of scientific attention, especially for those specieses with special habitats and in the critical state of distribution. Brachymystax lenok tsinlingensis is the southernmost salmonidae fish in the world, which has been listed as a second class state protected wild animal in China. It is an endangered freshwater fish land-locked and confined to cold-water mountain streams and rivers. Research on thermal physiology of B. lenok tsinlingensis is not only the urgent need for its conservation, but also has important research value and special significance for understanding the adaptive evolution of stenothermal fish in response to climate change. In this project, we scheme to study the effects of temperature on the phenotypes of B. lenok tsinlingensis that are closely associated with fitness, such as growth performance, swimming ability, metabolic characteristics, thermal optima and thermal tolerance, for guidance in accordance with the latest theories of thermal physiology. The main contents of the project are as follows: (1) analysises on the spatial and temporal differences in B. lenok tsinlingensis' phenotypic characteristics that are temperature depended, (2) studies on the reaction norms of phenotypes to temperature, and the trade-off between phenotypes in response to thermal variation, (3) research on the thermal adaptation and plasticity of B. lenok tsinlingensis, and (4) harmful effects of thermal stress on B. lenok tsinlingensis. We aim to reveal the temperature-induced plasticity of phenotypic characteristics in B. lenok tsinlingensis, to discuss the metabolic function and evolutionary adaptation strategies of this species in warming environment, and to test the evolutionary trade-off hypothesis and the beneficial acclimation hypothesis. Additionally, the important theoretical basis for fish farming and ecological protection of B. lenok tsinlingensis is supposed to be provided.

在全球升温的背景下，生境特殊、处于临界分布状态的物种的温度适应性进化备受科学界关注。秦岭细鳞鲑是目前世界上分布最南端的鲑科鱼类，为典型的陆封型冷水性山麓鱼类，是国家Ⅱ级重点保护水生野生动物，开展该物种热生理学方面的研究对理解动物温度适应性进化具有重要的科研价值和特殊意义，同时也是物种保护的迫切现实需要。项目围绕温度对秦岭细鳞鲑热适应特性（最适性、耐受性）、代谢特征、游泳能力、生长性能等适合度紧密关联的表型特征的影响开展研究，包括：①秦岭细鳞鲑表型特征的时空差异及其温度依赖性；②秦岭细鳞鲑表型特征对温度的反应规范及其权衡；③秦岭细鳞鲑热适应特性与可塑性；④热胁迫对秦岭细鳞鲑的应激损伤。本课题旨在揭示秦岭细鳞鲑热适应特性，及其表型特征对温度的可塑性，探究升温背景下秦岭细鳞鲑的代谢功能与进化适应对策，验证"进化权衡"假说和"驯化有益"假说，并为该物种的养殖与生态保护提供理论基础。

秦岭细鳞鲑为国家Ⅱ级重点保护水生野生动物，由于其特殊的生境与分布状态，是研究动物温度适应性进化的理想模型。本项目探究了该物种行为、代谢功率及其运动能量学特征对温度的反应规范，测定了该物种对其栖息地关键环境因子（水温、溶解氧、水流速度）的生理临界值，揭示了该物种的热忍耐特征及其应对升温胁迫的行为响应模式和生理生化应答机制，比较分析了该物种在鲑科鱼类中特殊的热生理学特征。主要研究发现包括：秦岭细鳞鲑对水温变化反应灵敏，并在升温胁迫下表现出三级行为响应模式；在一定范围内，温度升高（12→18 ℃）对其临界游泳速度和最大代谢率无显著影响，但导致代谢范围减少、游泳效率下降，提示该物种代谢与运动的最适温度可能介于12和18 ℃之间；秦岭细鳞鲑应对低氧环境的生理可塑性较差，高温下静止代谢率增加可能是导致其低氧耐受能力降低内在机制之一；相较其它鲑科鱼类而言，秦岭细鳞鲑具有更强的耐高温能力以及更大的可塑性，推测这一现象主要与该物种的地理分布有关。项目研究成果不仅丰富了鱼类温度适应性进化的理论内涵，而且为该物种的养殖与生态保护提供了理论基础。