急性低盐胁迫对绿鳍马面鲀幼鱼存活、鳃组织结构及肝脏抗氧化能力的影响

Effects of acute low salt stress on survival,gill structure and hepatic antioxidant capacity of juvenile bluefin leatherjacket(Thamnaconus septentrionalis)

为揭示绿鳍马面鲀(Thamnaconus septentrionalis)幼鱼在低盐胁迫下的生理生化响应机制,试验设置3个盐度处理组(盐度15、20、25)和1个空白对照组(盐度30),对体质量为(20±5)g的绿鳍马面鲀幼鱼进行为期96 h的低盐胁迫试验,分别于胁迫试验后的24、48、72、96 h对幼鱼进行相关组织采样,分析急性低盐胁迫对绿鳍马面鲀幼鱼存活、鳃组织结构、鳃丝Na^(+)/K^(+)-ATP酶活性和肝脏抗氧化能力的影响。结果表明:在25~30盐度下,绿鳍马面鲀幼鱼的存活不受盐度影响,盐度小于20时对幼鱼存活有显著性影响(P<0.05),幼鱼在胁迫时间为24、48、72、96 h时所对应的低盐半致死盐度(LC 50)分别为5.649、7.058、10.041和10.260;与对照组(盐度30)相比,25盐度组幼鱼鳃组织出现轻微鳃小片弯曲、末端膨大和细胞空泡化等现象,20、15盐度组鳃组织则出现不同程度的鳃小片弯曲粗大、不规则排列、基部增生与融合、线粒体丰富细胞增多、细胞空泡化和上皮细胞破裂等现象;20、15盐度组幼鱼鳃丝Na^(+)/K^(+)-ATP酶活性和肝脏抗氧化能力显著高于对照组(P<0.05),酶活生化指标大多在72 h时达到最高,在96 h时降低,除谷胱甘肽过氧化物酶(GSH-PX)活性、抗超氧阴离子能力和抑制羟自由基能力外,25盐度组的其他抗氧化酶活性在96 h时与对照组无显著性差异(P>0.05)。研究表明,盐度为25~30时适宜绿鳍马面鲀幼鱼生活,盐度小于25时,幼鱼机体会发生一系列应激反应,幼鱼鳃组织结构产生不同程度的适应性变化,在低盐胁迫下幼鱼有一定的自我调节能力。

To probe into the physiological and biochemical response mechanisms of juvenile bluefin leatherjacket(Thamnaconus septentrionalis)under low-salt stress,survival,gill histological structure,gill filament Na^(+)/K^(+)-ATPase activity,and hepatic antioxidant capacity were determined in juvenile bluefin leatherjacket with body weight of(20±5)g exposed to acute salinity of 15,20,25 and 30(control group 30)for 24,48,72,and 96 h.The results showed that the survival of the juveniles was significantly affected by salinity below 20(P<0.05),without significant effect at salinity of 25 and 30.The juvenile bluefin leatherjacket had median lethal salinity(LC 50)of 5.649 for 24 h,7.058 for 48 h,10.041 for 72 h,and 10.260 for 96 h.Compared to control group 30,the gill of the juvenile in salinity 25 group was shown to be slight lamellae curvature,terminal expansion,and cell vacuolization,while gill in salinity 20 and 15 groups showed varying degrees of gill lamellae curvature and coarseness,irregular arrangement,basal hyperplasia and fusion,as well as increase in number of mitochondria-rich cells,cell vacuolization,and rupture of epithelial cells.There were significantly higher Na^(+)/K^(+)-ATPase activity and hepatic antioxidant capacity in salinity 20 and 15 groups than those in control group(P<0.05),with the maximal points in most of the biochemical indices of enzyme activities at 72 h and decrease at 96 h,without significant difference in other enzyme activities in salinity 25 group at 96 h compared to control group,except for GSH-PX activity,anti-superoxide anion capacity and inhibition of hydroxyl radical capacity(P>0.05).The findings indicated that the salinity of 25-30 was suitable for the juvenile,and that the juvenile experienced a series of stress reactions at salinity of below 25,with different extents of adaptive changes including activity of gill filament Na^(+)/K^(+)-ATPase,and the antioxidant capacity in liver.