低盐胁迫对黄姑鱼(Nibea albiflora)幼鱼鳃离子调节、呼吸代谢酶和皮质醇的影响

Effects of Low-Salinity Stress on the Ion Regulation, Respiratory Metabolic Enzymes and Serum Cortisol in the Gill of Nibea albiflora Juvenile

挑选平均体重为(5.0±1.4)g,平均全长为(8.3±0.8)cm的黄姑鱼(Nibea albiflora)幼鱼,进行低盐度胁迫试验,以23盐度组为对照组,设置9和16两个盐度胁迫组,在0、1、3、7 d进行取样。通过检测鳃Na^+/K^+-ATP酶(NKA)、Ca^(2+)-ATP酶、H^+-ATP酶、乳酸脱氢酶(LDH)、琥珀酸脱氢酶(SDH)活力以及血清皮质醇含量,研究低盐度对黄姑鱼离子调节和呼吸代谢的影响。结果显示,鳃NKA活力在盐度胁迫后出现显著增强(P<0.05);Ca^(2+)-ATP酶活力略有上升后即出现下降的变化,而H^+-ATP酶活力呈现上升后恢复的变化。血清皮质醇含量在低盐度胁迫后呈显著的波动变化(P<0.05),9和16盐度组的皮质醇水平交替上升。鳃LDH活力在低盐度胁迫后显著增强(P<0.05),且9盐度组增强程度大于16盐度组。鳃SDH活力先减弱然后增强,9盐度组在7 d时增强十分显著(P<0.05)。试验中,仅9盐度组出现实验鱼死亡两尾的情况,16及23盐度组黄姑鱼进食和活动均正常,9盐度组略差。研究表明,盐度降低可显著影响黄姑鱼幼鱼离子调节能力及呼吸代谢功能。盐度胁迫程度超过黄姑鱼适应能力与机体储备的承受范围会对机体造成伤害。

In this study Nibea albiflora juveniles with the average weight of（5.0±1.4） g and the average length of（8.3±0.8） cm were divided into 3 salinity groups including salinity 23 as the control group and salinity 9 and 16 as the stress groups. Fish samples were collected on the 0, 1st, 3rd and 7th day. To evaluate the effects of low salinity on the ion regulation and respiratory metabolism of N. albiflora, we tested the changes in activities of Na＋/K＋-ATPase（NKA）, Ca2＋-ATPase, H＋-ATPase, lactate dehydrogenase（LDH） and succinate dehydrogenase（SDH） in gills, and the level of cortisol in the serum. In response to the low-salinity stress, the NKA activity increased significantly（P〈0.05）, and the Ca2＋-ATPase activity decreased after a slight increase in the beginning, and the H＋-ATPase activity first increased and then recovered to the initial level. The enhanced activities of NKA, Ca2＋-ATPase and H＋-ATPase could provide more energy for the ion transport to maintain the dynamic balance of the osmotic pressure. The cortisol level in the serum fluctuated significantly（P〈0.05） during the low-salinity stress, and the cortisol levels of salinity 9 or 16 group increased alternately. The LDH activity in the gill increased significantly（P〈0.05）, and the activity of the salinity 9 group was higher than that of the salinity 16 group. The SDH activity in the gill frist increased and then decreased, and the activity of the salinity 9 group increased significantly on the 7th day（P〈0.05）. Environmental stress would affect the normal aerobic respiration of N. albiflora. Along with the osmotic adjustment, the need of oxygen increased, which may significantly enhance the SDH activity. Noticeably, two experimental fishes died in the salinity 9 group during experiment. The feeding and activity of N. albiflora juveniles in the salinity 16 and 23 groups were normal,whereas they were impaired in the salinity 9 group. Our results suggested that low salinity could have significant effects on the ion regulation and respiratory metabolism of N. albiflora. Excessively low salinity may overwhelm the adaption ability of N. albiflora and cause harm to the health of the fish.