温度对红尾沙蜥代谢昼夜节律的影响

Effect of Temperature on the Circadian Rhythms of Metabolism in Phrynocephalus erythrurus

爬行动物很多生理、生化和行为指标都表现出昼夜节律。代谢昼夜节律不仅涉及内在因子的固有控制,而且受到多种外部因素的影响。为了探究温度对代谢昼夜节律的影响,在恒定的温度下(18℃和28℃)测定了红尾沙蜥Phrynocephalus erythrurus体温、心率、标准代谢率(SMR)和血糖浓度的昼夜变化。结果表明:(1)在2个温度下红尾沙蜥体温没有明显的昼夜变化;(2)昼间SMR明显高于夜间,18℃下SMR水平以及SMR昼夜变化的范围都低于28℃下的结果;(3)心率的变化也与代谢率的变化一致,但最低点提前了2 h;(4)28℃下的血糖浓度整体水平显著高于18℃下的,而波动规律却不同:28℃条件下白天平均值高于晚上,血糖浓度在16∶00显著高于20∶00、00∶00和12∶00;18℃条件下,血糖浓度在20∶00和08∶00明显低于00∶00和12∶00(P<0.05),而在04∶00和16∶00处于中间水平。该研究证实了红尾沙蜥SMR、心率和血糖浓度等生理生化指标也存在明显的昼夜节律,虽然这种现象受环境温度的影响,但主要还是由内在因子决定,这可能与某些激素的分泌活动有关。

Many biochemical,physiological,and behavioral parameters of reptiles showed daily fluctuations. Circadian rhythms of metabolism involved not only in the control of endogenous factors but also in the effects of various exogenous factors. To test the influence of temperature on the circadian rhythms of metabolism,the variation of body temperature,heart rate,standard metabolic rate（ SMR） and plasma glucose concentration in Phrynocephalus erythrurus under two temperature regimes（ 18 ℃ and 28 ℃） were investigated. Circadian rhythms were present in the SMR of P. erythrurus with higher values during the day than that during the night in constant conditions and the magnitude of the daily change was reduced at18 ℃. Additionally,the variation of heart rate was consistent with SMR except the nadir which came earlier at 18 ℃,implying a metabolic suppression in the low temperature. However,the body temperature did not show obvious circadian rhythm at constant conditions. The plasma glucose concentration at 28 ℃ was significantly higher than that at 18 ℃ with different circadian fluctuation： the value at 16∶ 00 was significantly higher than that at 20∶ 00,00∶ 00 and 12∶ 00 under 28 ℃. However,the values at 20∶ 00 and 08 ∶ 00 were significantly lower than that at 00 ∶ 00 and 12 ∶ 00 under 18 ℃,and the values at04∶ 00 and 16∶ 00 were moderate. The present study confirmed the circadian rhythms in the SMR,heart rate and plasma glucose concentration of P. erythrurus. The control of some endogenous factors played major role in the circadian rhythms of metabolism,while temperature had notable effects in entraining these rhythms,which may be associated with the secretion of some hormones.