高温—最佳温度循环对褐牙鲆生长、能量分配和身体成分的影响

The growth,energy allocation,and body composition of the brown flounder (Paralichthys olivaceus) during the cycles of high temperature-optimal temperature operation

环境温度短周期波动对鱼类的生长和能量代谢有重要影响,实验在室内可控条件下,对褐牙鲆幼鱼在经历高温-最佳温度循环的生长与能量分配进行了研究。在为期40d的实验中,驯养于20℃的褐牙鲆幼鱼在每个为期10d的循环中分别经历0d(H0)、2d(H2)、4d(H4)、6d(H6)和8d(H8)的26.5℃高温胁迫后,剩余的天数恢复到最佳温度(20℃)下养殖。实验结束时,经历不同天数高温胁迫的各处理组的褐牙鲆幼鱼以干重、湿重、蛋白质和能量表示的鱼体重均显著小于对照组(H0)。实验期间摄食量少和分配于生长的能量减少是导致经历高温胁迫的处理生长减慢的主要原因。经历高温胁迫的处理组的摄食量都显著低于对照组,但摄食率、消化率以及饲料转化效率都与对照组无明显差异。经受高温处理的H2、H4和H6组分配于生长的能量与对照组没有显著差异,但H4组的能量损失于粪便最多,H6组的能量损失于排泄的比例最高。H8组褐牙鲆幼鱼个体分配于生长的能量比例显著低于其他处理,代谢消耗的能量比例显著高于其他处理。经历不同温度循环处理的褐牙鲆幼鱼单位体重日摄食能与对照组相比没有显著差异,但分配于生长的能量却显著低于对照组。结果表明,褐牙鲆幼鱼对高温-最佳温度循环的适应能力较差,生长受到温度周期波动的抑制。

Short-period fluctuations in ambient temperature have a major impact on the growth and energy metabolism of fish.Under indoor controlled conditions,the growth and energy distribution of the brown flounder （ Paralichthys olivaceus） juveniles undergoing the cycles of high temperature-optimal temperature operation were investigated.During a single10-day cycle,the 20 ℃ acclimated juvenile brown flounder were cultured at high temperature（ 26.5 ℃） for different days as follows：0 d（ H0） ,2 d（ H2） ,4 d（ H4） ,6 d（ H6） ,and 8 d（ H8） ,and then maintained at 20 ℃ （ optimal temperature） for the remaining days.The fish were stocked in five recirculating systems and each system was equipped with three aquaria（ 80 cm × 50 cm × 35 cm,about 140 L） .Aeration was continually provided to keep the dissolved oxygen content above 5.5 mg/L.The salinity of the seawater was 30 and pH was 7.5±0.3.A photoperiod of 14 L∶ 10 D was adopted during the experiment.The fish were cultured for 4 cycles（ 40 d） and at the end of the experiment period,the body weight of fish which experienced different periods of high temperature exposure expressed in dry mass,wet mass,protein,and energy were all significantly lower than those of control group （ H0 ） .The lipid contents of the final fish which experienced high temperature were significantly higher than those of H0.Similar trend was observed in the protein contents of the final fish,except that H6 was slightly lower than H0.Through the experimental period, less feed ingestion and smaller fraction of energy allocated to growth mainly depressed the growth of fish which experienced different periods of high temperature exposure.The feed ingestion of the fish which experienced different periods of high temperature exposure was slightly lower than that of the controls,but the feeding rate, digestibility and food conversion efficiency were not significantly different from those of the control group.The energy allocated to growth in H2,H4,and H6 was not significantly different from H0.The highest proportion of energy lost in feces and excretion appeared in H4 and H6 respectively.The energy distribution in the growth in H8 was significantly lower than other treatments and its proportion of metabolic energy consumption was significantly higher than other treatments.The daily unit body weight energy ingestion of the fish which experienced different periods of high temperature exposure were was significantly different from H0,but the energy allocated to growth was significantly lower than that of H0.It could be concluded that the complete and over compensatory growth can not be achieved in similar high-optimal temperature operation.The above results indicated that the juvenile brown flounder showed poor flexibility to the cycle of high-temperature-optimum-temperature operation and temperature fluctuation would impact their growth.