水体低氧对香鱼幼鱼生长和消化酶活性的影响

Effects of Hypoxia on Growth and Activities of Digestive Enzymes of Juvenile Sweet Fish(Plecoglossus altivelis)

水体溶氧量是影响鱼类的重要环境因子,本研究检测了不同水平的低溶氧胁迫对香鱼幼鱼生长和消化酶活性的影响。结果显示:低氧胁迫后香鱼幼鱼生长受到抑制,溶氧量分别为4.5 mg/L和3.0 mg/L的两组实验鱼在胁迫7 d、14 d和21 d时的体重均显著小于溶氧量为7.5 mg/L的对照组(P<0.05),其中胁迫21 d时两组实验鱼的体重分别比对照组鱼的体重轻10.89%和20.73%;胁迫0~7 d期间两个实验组鱼的体重均为负增长(增重率分别为-2.30%、-4.78%),而对照组鱼的体重为正增长(增重率21.31%);胁迫7 d后两个实验组的鱼均恢复生长,且7~14 d期间的体重增重率均大于对照组,表现为补偿性生长;胁迫14~21 d期间溶氧4.5 mg/L的实验组的增重率与对照组相当,溶氧3.0 mg/L的实验组的增重率则略低于对照组。此外,低氧胁迫下两个实验组的淀粉酶、胃蛋白酶、脂肪酶活性均较对照组显著降低(P<0.05),而胰蛋白酶活性与对照组差异不显著(P>0.05)。其中,胃蛋白酶活性受低氧影响最大,胁迫21 d时两个实验组的胃蛋白酶活性分别仅为对照组的58.40%、62.34%,而淀粉酶活性已恢复至与对照组相当的水平,脂肪酶活性也有所恢复。由此表明,低氧胁迫会降低香鱼幼鱼消化酶活性,阻碍鱼体生长,同时鱼体对低氧环境也有一定的适应性,表现为在低氧环境下生活一段时间后消化酶活性有所恢复,鱼体出现一定程度的补偿性生长。

Dissolved oxygen(DO) in water is an important environmental factor for fish. Herein, growth and digestive enzyme activities of juvenile sweet fish(Plecoglossus altivelis) were analyzed under different levels of hypoxia stress. The results showed that the growth of larval P. altivelis was suppressed. The body weights of the two hypoxia stress groups(DO=4.5 mg/L and 3.0 mg/L, respectively) were both significantly low-er than that of the control group(DO=7.5 mg/L)(P<0.05), losing 10.89% and 20.73%, respectively, as compared with the control group at day 21. During the stress period of day 0 ~7, the two experimental groups showed negative growth(-2.30% and-4.78%, respectively) on body weight, while the control group showed positive growth(21.31%). After that, the growth of fish in the two experimental groups resumed and the weight gain rates were higher than that of the control group during day 7~14, showing compensatory growth. During day 14 ~21, the weight gain rate of DO =4.5 mg/L group was similar to that of the control group, while the weight gain rate of DO=3.0 mg/L group was slightly lower than that of the control group. Furthermore, the activities of amylase, pepsin and lipase were significantly decreased during hypoxia stress(P<0.05), while the activity of trypsin showed no significantly different changes compared with the control group(P>0.05). Pepsin was the most sensitive to hypoxia among these four digestive enzymes. After 21 days of hypoxia stress, the pepsin activities in DO=4.5 mg/L and DO=3.0 mg/L groups were only 58.40% and 62.34%, respectively, of the control level, while the amylase activity was restored to the same level as the control, and the lipase activity also got some recovery after the fish lived in low oxygen environment for a period of time. Altogether,hypoxia could reduce the digestive enzyme activity and restrain the growth of juvenile sweet fish, and the fish also showed some adaptability to hypoxia such as compensatory growth and partial recovery of digestive enzyme activities.