We evaluated the combined effects of temperature and salinity on the energy metabolism of Nile tilapia juveniles (Oreochromis niloticus, GIFT strain). We used a two-factor central composite experimental design (CCD) and response surface methodology (RSM) to test the effects of temperature (13-36°C) and salinity (0-20) on the oxygen consumption rate (OR), ammonia excretion rate (NR), and CO2 excretion rate (CR) under laboratory conditions. The linear effects of temperature and salinity, the quadratic effect of salinity, and the interaction between salinity and temperature had significant effect on OR, NR and CR (PO.05). The quadratic effect of temperature was not associated with changes in OR and CR (P>0.05). The model equations for OR, NR, and CR had R2 values of 0.958 1, 0.977 8, and 0.979 5, respectively (P<0.01), and could be used for prediction. The OR, NR, and CR were influenced more by temperature than by salinity. At lower salinities, energy metabolism was sensitive to changes in temperature, and OR, NR, and CR were higher around the iso-osmotic point. However, when salinity exceeded the iso-osmotic point, lower temperatures and higher salinity inhibited metabolism. The O : N ratio did not vary with temperature, but vary with salinity (P>0.05). Within the temerature range of 13-36°C and salinity range of 0-10, tilapia juveniles utilized protein-lipid- dominated metabolism. Conversely, the juveniles depended on lipid-dominated catabolism at salinity of 20. The mean respiratory quotient value was 0.752. Our results provide insight into the joint influence of temperature and salinity on the metabolism of tilapia juveniles and provides a bioenergetic basis for the study of how environmental factors govern the spatial and temporal pattern of energy distribution in this species.%在实验室条件下采用中心复合设计和响应曲面法,以影响能量代谢的2个重要环境因子(温度和盐度)为自变量,以耗氧率、排氨率与CO2排泄率为响应值,研究并探讨了温度(13～36℃)与盐度(0～20)对吉富罗非鱼幼鱼能量代谢的联合影响.结果表明,温度与盐度的一次效应、盐度的二次效应及其互作效应对耗氧率、排氨率与CO2排泄率均有显著影响(P＞0.05)；温度的二次效应对耗氧率和CO2排泄率没有显著影响(P＞0.05)；所考察因子与耗氧率、排氨率与CO2排泄率间二次多项回归方程的决定系数分别达到0.9581、0.9778和0.9795 (P＜0.01),可用于预测.温度效应较盐度明显,盐度较低时,能量消耗对温度变化较为敏感；在等渗点附近,耗氧率、排氨率和CO2排泄率较高;盐度超过等渗点时,低温和高盐环境对幼鱼的能量代谢有抑制作用.氧氮比(O∶N)随盐度变化而变化,温度对其没有显著影响(P＞0.05).当温度与盐度分别为13～36℃与0～10时,罗非鱼幼鱼主要依靠蛋白质和脂肪氧化供能;盐度为20时,脂肪成为主要供能物质；本实验条件下呼吸商的均值为0.752.本研究有助于更好地解释温度与盐度对罗非鱼新陈代谢的影响,同时可以为研究环境因子对能量的时空分配模式的改变提供生物能量学依据.
展开▼
