Physiological and Biochemical Thermoregulatory Responses in Male Chinese Hwameis to Seasonal Acclimatization: Phenotypic Flexibility in a Small Passerine

摘要

Many small birds living in regions with seasonal fluctuations and ambient temperaturestypically respond to cold by increasing metabolic thermogenesis, internal organ mass andthe oxidative capacity of certain tissues. In this study, we investigated seasonaladjustments in body mass, resting metabolic rate (RMR), evaporative water loss (EWL), themass of selected internal organs, and two indicators of cellular aerobic respiration(mitochondrial state-4 respiration and cytochrome oxidase activity) inChinese hwamei ( ) that had been captured in summer orwinter from Wenzhou, China. RMR and EWL were higher in winter than in summer. State-4respiration in the heart, liver, kidneys and pectoral muscle, as well as cytochrome oxidase activity in the liver, kidneys and pectoral muscle were alsohigher in winter than summer. In addition, there was a positive correlation between RMRand EWL, and between RMR and indicators of cellular metabolic activity in the heart,liver, kidneys and pectoral muscle. This phenotypic flexibility in physiological andbiochemical thermoregulatory responses may be important to the hwamei’s ability to survivethe unpredictable, periodic, cold temperatures commonly experienced in Wenzhou in winter.