To investigate the matebolize response of different physiological performances to decreased temperature of long term high-temperature-acclimated juvenile qingbo (Spinibarbus sinensis),the experimental fish were reared at 15 or 25℃ for 8 weeks,respectively;then the temperature of the 25℃ group was decreased to 15℃ (treatment group),and the temperature of the 15℃ group remained the same (control group).The thermal tolerance capacity (critical maximum temperature,CTmax and critical minimum temperature,CTmin),maximum sustainable swimming speed (critical swimming speed,Ucrit),spontaneous activities (percent time spent moving (PTM) and total distance moved (TDM)),specific dynamic action (peak postprandial metabolic rate (PMR)),and growth performance (feed rate,feed efficiency,and weight gain) of fish in both temperature groups were measured at 1,2,4,and 8 weeks after the temperature was decreased.There was no significant difference in cold tolerance capacity as suggested by CTmin between the treatment and control groups,whereas the heat tolerance capacity,as suggested by CTmax of the treatment group,was significantly higher than that of the control group one week after the temperature decrease,and thereafter there was no difference between the groups.The temperature decrease resulted in a significant improvement of spontaneous activities suggested by higher PTM and TDM than those of the control group (P ＜ 0.05),and such differences persisted throughout the experimental period.The Ucrit of the treatment group was significantly lower than that of the control group at 1 and 2 weeks after the temperature decrease,and the impaired swimming capacity disappeared after 4 weeks of temperature acclimation.The PMR and SDA duration did not show any differences between the treatment and control groups from 1 to 4 weeks after the temperature decrease.The food efficiency and weight gain of the treatment group were generally lower than those of the control group,although the treatment group unusually showed a higher food rate.This suggested that there were profound differences among response speeds of different physiological performances to decreased temperature,which were possibly related to differences in their ecological correlations and underlying mechanisms.The temperature decrease in the treatment group resulted in impaired growth performance,which was mainly due to the additional energy expenditure involved in thermal stress responses,regulation of physiological functions,and elevated spontaneous activities.%为了考查长期高温驯化的中华倒刺鲃(Spinibarbus sinensis)幼鱼快速降温后不同生理功能对低温环境的响应速率,将实验鱼分为2组分别在15℃和25℃条件下长期驯养(8周),随后25℃组快速降温至15℃(降温组),同时15℃组(恒低温对照组)温度保持不变;在降温后的第1、2、4和8周分别测定和比较降温组和恒温对照组实验鱼的温度耐受能力、游泳能力、自发活动水平、摄食代谢和生长性能等相关生理指标.结果显示:降温后,低温耐受能力(CTin)1周时就达到稳定与对照组不再有差异,而高温耐受能力(CTmax)2周时才达到稳定;与对照组相比,降温处理导致实验鱼自发活动水平(运动时间百分比,PTM和运动总距离,TDM)显著上升,且此差异持续整个驯化周期(P＜0.05);降温组的临界游泳速度(Critical swimming speed Ucrit)在降温的1-2周均显著小于对照组(P＜0.05),直到4周才达到稳定;降温组实验鱼特殊动力作用(Specific dynamic action SDA)持续时间和摄食后代谢峰值(Peak metabolic rate PMR)与对照组在降温1-4周均没有显著差异;尽管降温组有更高的摄食率,其食物转化效率和增重率均显著低于对照组(P＜0.05).研究表明:中华倒刺鲃在水体温度下降后,不同生理功能的稳定速率存在差异,这可能与不同生理功能的生态关联及内在机制的不同有关;降温处理导致机体生长受阻,其主要原因可能是由于应对环境温度变动的逆境胁迫、生理功能调整以及自发活动增加所导致的能量消耗上升所致.
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