许氏平鲉低氧耐受能力及血液学和鳃组织学变化

Hypoxia tolerance and alternation of hematology and gill morphology in black rockfish(Sebastes schlegelii)

为探明许氏平鲉低氧耐受能力及低氧胁迫过程中其血液生理生化指标和鳃组织形态结构变化,本研究分析了许氏平鲉临界氧分压(Pcrit)和失去平衡点(LOE)时溶解氧含量,观察了低氧胁迫和恢复溶解氧过程中呼吸行为和呼吸频率的变化,分析了血液生理[红细胞数目(RBC),白细胞数目(WBC),血红蛋白(Hb),红细胞积压(HCT)]、生化[葡萄糖、皮质醇]指标以及鳃组织形态学和鳃组织气体交换率(PAGE)变化。结果显示,在温度18℃、盐度30,pH值7.85的条件下,许氏平鲉[(88.01±5.34)g]Pcrit和LOE溶解氧含量分别为(3.96±0.11)和(2.60±0.21)mg/L。随着水体中溶解氧含量下降,血浆皮质醇和葡萄糖分别在LOE和Pcrit达到最高。许氏平鲉血液RBC、Hb和HCT在LOE达到最高。低氧过程中,许氏平鲉呼吸频率和PAGE分别于Pcrit和LOE达到最高,且低氧导致许氏平鲉鳃小片长度(SLL)、间距(ID)、周长显著增加;鳃小片宽度(SLW)则随水中溶解氧含量下降而变窄,在LOE处达到最小值。许氏平鲉鳃小片末端膨大、基质肥大、增生比例在低氧过程中显著增加。恢复正常溶解氧24 h后,上述各项检测指标恢复正常,与对照组无显著差异。实验中对照组各项指标无显著变化。研究表明,许氏平鲉对水体低溶解氧变化反应敏感,低氧应激导致其血液生理生化相关指标和鳃小片形态发生显著改变,恢复正常溶解氧24 h后可以显著缓解低氧胁迫应激。相关结果为研究许氏平鲉低氧耐受生理调控机制和高效健康养殖提供了理论依据和技术支撑。

Dissolved oxygen is an important environmental factor affecting the survival of fish.In this study,the value of dissolved oxygen at critical oxygen partial pressure(Pcrit)and loss of equilibrium(LOE),respiratory rate,plasma cortisol,glucose,white blood cell(WBC),red blood cell(RBC),hemoglobin(Hb),hematocrit(HCT)and the alternation of gill morphology and related parameters[lamellar length(SLL)and width(SLW),interlamellar distance(ID)and perimeter]as well as the proportion of secondary lamellae available for gas exchange(PAGE)were observed during hypoxia to illustrate hypoxia tolerance,physio-biological response and morphological changes in the gills of Sebastes schlegelii during hypoxia stress.Results showed that the value of dissolved oxygen at Pcrit and LOE of S.schlegelii at(88.01±5.34)g were(3.96±0.11)mg/L and(2.60±0.21)mg/L respectively under the condition of water temperature(15.6±0.2)℃,pH value 7.85,and salinity 30.0.The PAGE and respiratory frequency increased first and then decreased,the highest value respectively obtained at Pcrit and LOE(P<0.05)throughout hypoxia stress.Meanwhile,plasma cortisol and glucose levels significantly increased,the highest values observed at LOE and Pcrit(P<0.05).In blood physiology,Hb,HCT,WBC similar results like plasma cortisol,with the highest value at LOE(P<0.05),whereas RBC remained unchanged during hypoxia stress.Besides,the SLL,ID,Perimeter of gills increased significantly during hypoxia stress,and reached the maximum value at LOE point(P<0.05)either;the SLW decreased and reached the minimum value at the LOE(P<0.05).At the same time,the clubbing,hypertrophy,hyperplasia and epithelial cell edema were observed in the secondary lamella.All the aforementioned parameters recovered to normal levels after re-oxygenation 24 h in S.schlegelii.In conclusion,S.schlegelii are sensitive to low dissolved oxygen,have numbers of changes in hematology and morphology for hypoxia stress and reduce hypoxia stress after reoxygenation treatment for 24 h.These findings expand current knowledge on hypoxia tolerance and help in the management of S.schlegeli in captivity.