Qingdao Key Laboratory for Marine Fish Breeding and Biotechnology, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, No. 106 Nanjing Road, Qingdao, 266071, People's Republic of China.
Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China.
Fish Physiol Biochem. 2021 Aug;47(4):1133-1147. doi: 10.1007/s10695-021-00970-5. Epub 2021 May 31.
Hypoxia has gradually become common in aquatic ecosystems and imposes a significant challenge for fish farming. The loss of equilibrium (LOE), 50% lethal time (LT50), plasma cortisol, glucose, red blood cells (RBC), hemoglobin (Hb), gill histological alteration, and related parameters (lamellar length [SLL] and width [SLW], interlamellar distance [ID], basal epithelial thickness [BET], lamellar surface area [LA], and gill surface area [GSA]); respiratory rate; the proportion of the secondary lamellae available for gas exchange (PAGE); and hypoxia-inducible factor (hif-1α, hif-2α) mRNA expression were determined during progressive hypoxia and reoxygenation (R-0, R-12, R-24 h) to illustrate the underlying physiological response mechanisms in black rockfish Sebastes schlegelii. Results showed that the DO concentration significantly decreased during progressive hypoxia, while DO at LOE and LT50 were 2.42 ± 0.10 mg L and 1.67 ± 0.38 mg L, respectively. Cortisol and glucose were significantly increased at LOE and LT50, with the highest levels observed at LT50, and then gradually recovered to normal within reoxygenation 24 h. RBC number and Hb results were like those of glucose. Hypoxia stress resulted in lamellar clubbing, hypertrophy, and hyperplasia. Respiratory frequency significantly increased at LOE and decreased at LT50. Lamellar perimeters, SLL, ID, LA, GSA, and PAGE, significantly increased at LOE and LT50, with the highest values observed at LT50. However, SLW and BET significantly decreased at LOE, LT50, and R-0. These parameters recovered to nearly normal levels at R-24 h. hif-1α mRNAs in gill and liver were significantly upregulated at LOE and LT50, and recovery to normal after reoxygenation 24 h. hif-2α mRNAs in gill was similar to that of hif-1α, whereas hepatic hif-2α mRNAs remained unchanged during hypoxia-reoxygenation. These results indicated that progressive hypoxia stress elevated RBC number, Hb, cortisol, and glucose levels, induced the alteration of gill morphology, increased LA and GSA, stimulated respiratory frequency and PAGE, and upregulated the transcription of hif-1α and hif-2α in gill and liver. Reoxygenation treatment for 24 h alleviated the stress mentioned above effects. These findings expand current knowledge on hypoxia tolerance in black rockfish Sebastes schlegelii.
缺氧在水生生态系统中逐渐变得普遍，给鱼类养殖带来了重大挑战。平衡丧失 (LOE)、50%致死时间 (LT50)、血浆皮质醇、葡萄糖、红细胞 (RBC)、血红蛋白 (Hb)、鳃组织学改变以及相关参数 (板层长度 [SLL] 和宽度 [SLW]、板层间距离 [ID]、基底上皮厚度 [BET]、板层表面积 [LA] 和鳃表面积 [GSA])；呼吸率；用于气体交换的次级板层比例 (PAGE)；以及缺氧诱导因子 (hif-1α、hif-2α)mRNA 表达在进行性缺氧和再氧合 (R-0、R-12、R-24 h) 期间确定，以说明黑鲷 Sebastes schlegelii 中潜在的生理反应机制。结果表明，DO 浓度在进行性缺氧期间显著下降，而 LOE 和 LT50 时的 DO 浓度分别为 2.42±0.10 mg L 和 1.67±0.38 mg L。皮质醇和葡萄糖在 LOE 和 LT50 时显著增加，LT50 时达到最高水平，然后在再氧合 24 h 内逐渐恢复正常。RBC 数量和 Hb 结果与葡萄糖相似。缺氧应激导致板层变钝、肥大和增生。呼吸频率在 LOE 和 LT50 时显著增加，在 LT50 时降低。LOE 和 LT50 时板层周长、SLL、ID、LA、GSA 和 PAGE 显著增加，LT50 时达到最高值。然而，SLW 和 BET 在 LOE、LT50 和 R-0 时显著降低。这些参数在再氧合 24 h 时恢复到接近正常水平。LOE 和 LT50 时，鳃和肝脏中的 hif-1α mRNA 显著上调，再氧合 24 h 后恢复正常。鳃中的 hif-2α mRNA 与 hif-1α 相似，而肝 hif-2α mRNA 在缺氧-再氧合过程中保持不变。这些结果表明，进行性缺氧应激会增加 RBC 数量、Hb、皮质醇和葡萄糖水平，引起鳃形态改变，增加 LA 和 GSA，刺激呼吸频率和 PAGE，并上调鳃和肝脏中 hif-1α 和 hif-2α 的转录。再氧合处理 24 h 可缓解上述应激作用。这些发现扩展了黑鲷 Sebastes schlegelii 对缺氧耐受性的现有知识。
