白头鹎的代谢率与器官重量在季节驯化中的可塑性变化

Adaptive Plasticity in Metabolic Rate and Organ Masses among Pycnonotus sinensis,in Seasonal Acclimatization

动物能量代谢的生理生态特征与物种的分布和丰富度密切相关,基础代谢率(BMR)是恒温动物维持正常生理机能的最小产热速率,是动物在清醒时维持身体各项基本功能所需的最小能量值,是内温动物能量预算的重要组成部分。本研究测定了白头鹎(Pycnonotus sinensis)的BMR、内部器官(肝、心、肌胃、小肠、肾和整体消化道)和肌肉的重量,分析了白头鹎内部器官和肌肉重量的季节性变化及与BMR的关系。方差分析表明,白头鹎的BMR存在明显的季节性变化,冬季较高,夏季最低。其内部器官及肌肉重量的变化同样有明显的季节性。相关分析表明,白头鹎的BMR与肝、心、消化道等内部器官和肌肉重量存在明显的相关性。

The necessity of maintaining energy balance is one of the major factors influencing the abundance and distribution of small birds, and many morphological, physiological and behavioral adaptations are related to energy utilization. Basal metabolic rate （BMR） is the rate of energy transformation in a rest, awake and postabsorptive state in the absence of thermal stress, and is the minimum metabolic rate of animals maintaining normally physiological function. Theoretically, BMR limits might be set by central organs （primarily visceral organs such as the pulmonary＇, cardiovascular, digestive or excretory systems ） or by peripheral organs （primarily skeletal muscles） that support peripheral effectors. These ideas represent the ＇central limitation hypothesis＇ and the ＇peripheral limitation hypothesis,＇ respectively. In this study, we measured seasonal changes in BMR and organ mass, and evaluated the relationship between BMR, organ mass in Chinese Bulbul （Pycnonotus sinensis）. The results were used to test the ＇energy demand＇ hypothesis for adjustments in metabolic rate. The energy demand hypothesis supposed that birds adjust the size of their internal organs relative to food intake, a correlate of energy demand. Winter and autumn bulbuls demonstrated significantly higher BMR than their spring and summer counterparts. Winter and autumn birds also had higher liver, heart, gizzard, small intestine, kidneys, total digestive tract and muscle than spring and summer birds. These data support the hypothesis that prominent winter increases in BMR are components of winter acclimatization in Chinese Bulbuls and that seasonal changes in metabolism in bulbuls are similar to those for other small wintering birds. Meanwhile, these data test the hypothesis that central and peripheral organs have a significant positive relationship with BMR.The relationship between BMR and internal organs could be due to either （or both） increased energy demand or seasonal shifts in diet.