中国特有分布种画眉鸟和红嘴相思鸟的适应性产热特征与机制

Fluctuating environments necessitate adjustments in physiology, behavior and morphology in small birds. Adjustments of thermoregulatory mechanisms presumably promote the survival of birds subjected to seasonal changes in their natural environment, including temperature, photoperiod, and food quality and availability. Phenotypic flexibility refers to phenotypic changes that are reversible, temporary, and repeatable. Resident birds of temperate climates provide a natural experiment in phenotypic flexibility, and in these birds winter increments of thermogenic capacity and cold tolerance are often associated with changes in exercise or nutritional organ masses and cellular aerobic capacity. Seasonal adjustment of cellular aerobic capacity potentially involves modulation of activities of key catabolic enzymes in oxidative pathways and/or activities of enzymes and transporters involved in substrate mobilization and delivery pathways. Thyroid hormones may regulate thermogenesis, especially basal and cold-induced thermogenesis in birds and mammals. Elevation of thyroid hormones in plasma increases the obligatory and facultative thermogenesis in some avian species. Thyroid hormones can also enhance adaptive thermogenesis by influencing several aspects of energy metabolism, such as substrate cycling, ion cycling, and mitochondrial proton leakage. Hwameis (Garrulax canorus) and red-billed leiothrix (Leiothrix lutea) belong to Passeriformes, Timaliidae. As an endemic Asian species, Hwameis mainly inhabit central and southern China, northern Indochina, Hainan and Taiwan. Within their ranges, Hwameis preferentially inhabit scrubland, open woodland, secondary forest. Due to the male's elaborate songs, Hwameis are one of the most popular caged birds in the global Chinese community. In this study, we used an integrative approach to investigate whether seasonal phenotypic variation is associated with physiological, hormonal, or biochemical differences in the hwamei and red-billed leiothrix. In the final, from the perspective of energy, we clarify the metabolism and adaptive strategy in hwamei and red-billed leiothrix, and provide a scientific basis for Timaliidae which adapt to different environments.

鸟类的代谢产热特征与其地理分布的气候带和栖息环境密切相关，某一地区某种鸟类的代谢水平与总体鸟类代谢一般模式的差异，可以反映出该物种对环境独特的适应机制和进化对策，体现出生物多样性与环境相适应的关系。中国现有画眉科鸟类分别占世界属、种的57.4%和45.9%，是画眉科分布的辐射中心，画眉科鸟类不仅是我国野生动物资源的一个重要组成部分，而且对全球生物多样性保护具有重要意义。本项目以画眉鸟和红嘴相思鸟为研究对象，以进化生理学的理论为基础，从不同组织层次（整体、器官、细胞及分子水平等）上整合研究画眉鸟和红嘴相思鸟的代谢产热特征；探讨外部环境因素（温度和光周期等）和内部调节因子（甲状腺激素、鸟类解偶联蛋白和瘦素等）对画眉鸟和红嘴相思鸟适应性产热的影响，确定限制其地理分布的产热特征，揭示其生存对策及适应机制，为对其管理与保护提供科学依据。

本项目从自然环境的季节性驯化、实验室的温度光周期的适应实验及甲状腺激素亢进实验探讨画眉鸟和红嘴相思鸟适应性产热，以进化生理学的理论为基础，从不同组织层次（整体、器官、细胞及分子水平等）上整合研究画眉鸟和红嘴相思鸟的代谢产热特征；探讨外部环境因素和内部调节因子对画眉鸟和红嘴相思鸟适应性产热的影响。研究结果表明：①冬季画眉和红嘴相思鸟有更高的体重、基础代谢率和代谢活性器官重量；画眉和红嘴相思鸟肌肉和肝脏中细胞色素氧化酶活力和线粒体呼吸冬季显著高于夏季，心脏中仅线粒体呼吸冬季显著高于夏季，肾脏中细胞色素氧化酶活力冬季显著高于夏季。画眉和红嘴相思鸟表现出对季节性驯化的生理反应，利用这种能力应对野外环境温度的波动；②甲状腺素对画眉体重没有显著影响，但甲亢组画眉的代谢率比对照组画眉的代谢率明显升高，甲状腺激素使肝脏和肌肉的线粒体状态呼吸及细胞色素氧化酶活力明显升高；③低温增加画眉和红嘴相思鸟的代谢产热，肌肉、肝脏、心脏和肾脏的状态四呼吸和细胞色素氧化酶的活力在冷适应后也显著升高，并与基础代谢率显著相关，表明画眉和相思鸟表现出对温度适应的生理反应，利用这种能力应对野外环境温度的波动；④温度和光周期实验表明低温影响画眉的体重、代谢产热、器官的重量（肾脏和小肠）；低温组肾脏和肝脏组织线粒体状态呼吸以及细胞色素氧化酶活力显著高于暖温组，小肠细胞色素氧化酶活力受低温影响显著增加。相比于光周期，环境因子中温度的改变似乎是驱动画眉鸟代谢产热季节性变化的主要因素，且画眉鸟代谢产热对温度变化的响应更敏感。适应性产热是鸟类生理生态学的重要指标，能反映鸟类不同物种及同种不同个体间的能量消耗水平，确定限制其地理分布的产热特征，揭示其生存对策及适应机制。