急性低盐胁迫对斜带石斑鱼幼鱼存活、血清离子浓度和内分泌激素水平的影响

Effects of acute low salinity stress on survival,concentrations of ions and endocrine hormones in serum of Epinephelus coioides juveniles

为探究急性低盐胁迫对斜带石斑鱼(Epinephelus coioides)幼鱼存活、血清离子浓度和激素水平的影响,将斜带石斑鱼幼鱼从盐度30(对照组)的水体直接转移至盐度0、5、10、20的水体中,于2 h、6 h、12 h、48 h和72 h检测幼鱼血清中的钠离子(Na^+)、钾离子(K^+)、氯离子(Cl^-)浓度和生长激素(GH)、催乳素(PRL)、皮质醇(COR)水平的变化,并记录幼鱼存活情况。结果显示,血清Na^+和Cl^-浓度随盐度增加显著上升(P<0.05)。盐度0组和对照组血清Na^+浓度随实验时间变化不大,较稳定(P>0.05);而盐度5和盐度10组血清Na^+浓度在6 h降低,随后升高并保持稳定(P<0.05);盐度20组血清Na^+浓度随时间的延长出现显著波动(P<0.05)。随时间延长Cl^-浓度在盐度0组呈显著下降趋势(P<0.05),在盐度5、10和20组和对照组变化不明显(P>0.05)。K^+浓度在盐度0组显著高于其它组(P<0.05)。随时间延长K^+浓度在盐度0组先升后降(P<0.05),而在盐度5、10和20组以及对照组则先降后升(P<0.05)。GH水平在盐度20和对照组显著高于其它3组(P<0.05)。随时间延长GH水平在盐度0、5和10组呈先下降至6 h处达到最低点,而后上升的趋势(P<0.05),而在盐度20和对照组无显著变化(P>0.05)。PRL在各试验组显著高于对照组(P<0.05)。随时间延长各试验组血清PRL水平先下降后上升至12 h达到最大值后又下降(P<0.05),最后趋于稳定。COR水平在盐度0、5和10组显著高于盐度20和对照组(P<0.05)。随时间延长在盐度0、5和10组的变化规律与PRL水平类似,而在盐度20和对照组无显著变化(P>0.05)。随时间延长在盐度0组幼鱼死亡率逐渐升高,72 h内全部死亡;盐度5组幼鱼在实验期间仅有极少数死亡,而其它组幼鱼无死亡情况,这表明斜带石斑鱼幼鱼能够适应在盐度低至5的急性胁迫下存活,但在淡水急性胁迫条件下不能长时间存活。

In order to study the relationship between serum ions and osmoregulatory function of gill mitochondrion-rich cells（MRCs） , and the function of serum hormones in gill MRCs osmoregulation, effects of acute low salinity stress on survival, concentrations of ions and hormones in serum of Epinephelus coioides juveniles were studied. E. coioides juveniles [ body weight （ 16.68 ± 2.62 ） g ] were directly transferred to water with salinities at 0, 5, 10, 20 from water with salinity at 30 （ the control group）. Na＋ , K＋ , Cl- concentrations, growth hormone （GH） , cortisol （COR）, prolactin （PRL） in serum and the deaths of E. coioides juveniles were investigated at 2 h, 6 h, 12 h ,24 h, 48 h, and 72 h after transferring. The results showed that death rate of E. coioides juveniles in water with salinity 0 was gradually increasing , and E. coioides were all dead at 72 h, while E. coioides in other groups were living well. Na＋ and Cl- concentrations significantly increased with the rise of water salinity（P 〈 0.05 ）. Na ＋ concentration in water with salinity 0 and the control group remained stable （ P 〉 0.05 ）, but the other groups were just the opposite , they demonstrated a similar tendency of decreasing first to its lowest value at 6 h and increasing thereafter（ P 〈 0.05 ）. C1 - concentration in serum increased with the rise of water salinity, and showed a downward trend in the water with salinity 0 （ P 〈 0.05 ） , while there was no significant change at salinities 5, 10, 20 and the control group（ P 〉 0.05 ）. K＋ concentration in water with salinity 0 was significantly higher than that at other salinities （P 〈 0.05 ）. K＋ concentration in serum in water with salinity 0 increased and then decreased（P 〈0.05）, while K＋ concentration in water with salinities of 5, 10, 20 and the control group showed a downward trend and then increased （ P 〈 0.05 ） , and there was no significant difference among them （ P 〉 0.05 ）. GH level increased with the rise of water salinity , and there was no significant change in GH in the water with salinity of 20 and the control group （P 〉 0.05 ） , but significantly higher than that at salinities 0, 5 and 10. PRL displayed a significant downward with the rise of salinity（ P 〈0.05 ） , and in salinity stress groups displayed a similar trend of decreasing first, increasing to its peak at 12 h, then decreasing （P 〈 0.05 ）, and being stable at last. COR also showed a significant downward with the rise of salinity, and displayed the same trend in water with salinities of 0 , 5 and 10 as PRL, but significantly higher than that at salinity 20 and the control group （ P 〈 0.05 ）. In conclusion, when adapted to the low salinity water, if the osmotic pressure is beyond the physiological permeability range , the osmoregulatory function of gill MRCs will be damaged. So in this study, E. coioidesjuveniles can not survive for long in fresh water. permeability range of fish, gill MRCs will play a balance . And in this process, the serum hormones But if osmotic pressure is in the normal physiological crucial role in osmoregulation through maintaining ionic play an important role, so that in this study E. coioides juveniles can adapt to water with salinity≥5.