Zheng Wei-Hong, Liu Jin-Song, Swanson David L
School of Life and Environmental Sciences, Wenzhou University, Wenzhou 325035, China; and Zhejiang Provincial Key Lab for Subtropical Water Environment and Marine Biological Resources Protection, Wenzhou 325035, China; 2Department of Biology, University of South Dakota, 414 East Clark Street, Vermillion, South Dakota 57069.
Physiol Biochem Zool. 2014 May-Jun;87(3):432-44. doi: 10.1086/675439. Epub 2014 Apr 9.
Survival of small birds in fluctuating environments is facilitated by seasonal metabolic and morphological flexibility. Chinese bulbuls Pycnonotus sinensis show winter increases in resting metabolic rate (RMR), nutritional organ masses, and liver and muscle cellular aerobic capacity relative to summer. In this study, we build on these findings from previous studies by measuring seasonal adjustments in body mass (Mb), RMR, nutritional and exercise organ masses, and several physiological, biochemical, and hormonal markers over the entire annual cycle in wild-trapped Chinese bulbuls from Wenzhou, China. Furthermore, we analyzed the relationships between variation in organ masses and cellular aerobic capacity and variation in RMR in individual birds. Mb and RMR were higher in spring (March-May) and winter (December-February) than in summer (June-August). The dry masses of several nutritional organs and mitochondrial protein content, state 4 respiration, and cytochrome c oxidase (COX) activity in liver and muscle were all heightened in winter relative to other seasons. In addition, dry masses of heart and pectoral muscle, but not nutritional organs, and biochemical markers of cellular aerobic capacity in liver and muscle were positively correlated with RMR. Plasma triiodothyronine (T3) concentration was higher in winter and spring than in summer and autumn, and it was positively correlated with RMR, mitochondrial protein content, state 4 respiration, and COX activity in liver and muscle. These results suggest that seasonal changes in nutritional and exercise organ masses and liver and muscle cellular aerobic capacity interact to promote seasonal metabolic flexibility in Chinese bulbuls. T3 appears to promote these seasonal thermoregulatory adjustments.
季节性的代谢和形态灵活性有助于小型鸟类在波动的环境中生存。相对于夏季，白头鹎冬季的静息代谢率（RMR）、营养器官质量以及肝脏和肌肉细胞的有氧能力均有所增加。在本研究中，我们基于先前研究的这些发现，对从中国温州野外捕获的白头鹎在整个年度周期内的体重（Mb）、RMR、营养和运动器官质量以及一些生理、生化和激素指标进行了季节性测量。此外，我们分析了个体鸟类器官质量和细胞有氧能力的变化与RMR变化之间的关系。春季（3月至5月）和冬季（12月至2月）的Mb和RMR高于夏季（6月至8月）。相对于其他季节，冬季时几种营养器官的干质量、肝脏和肌肉中的线粒体蛋白含量、状态4呼吸以及细胞色素c氧化酶（COX）活性均有所提高。此外，心脏和胸肌的干质量（而非营养器官）以及肝脏和肌肉中细胞有氧能力的生化指标与RMR呈正相关。血浆三碘甲状腺原氨酸（T3）浓度在冬季和春季高于夏季和秋季，并且与肝脏和肌肉中的RMR、线粒体蛋白含量、状态4呼吸以及COX活性呈正相关。这些结果表明，营养和运动器官质量以及肝脏和肌肉细胞有氧能力的季节性变化相互作用，促进了白头鹎的季节性代谢灵活性。T3似乎促进了这些季节性体温调节调整。
