Abstract:
Background In recent years, factors such as extreme climate, high-density aquaculture and water eutrophication have led to increased fluctuations in dissolved oxygen concentration in water bodies, and hypoxia in aquatic animals has become more frequent. Pike perch (Sander lucioperca) is an economically important fish species highly sensitive to hypoxic conditions.
Objective To investigate the effects of hypoxia stress on the gill tissue structure, antioxidant capacity and gene expression of S. lucioperca.
Methods Acute stress (0 h, 6 h, 48 h) and reoxygenation (6 h) experiments were conducted to analyze the structural changes, oxidative stress status and gene expression differences of gill tissues in S. lucioperca.
Results Hypoxic stress resulted in significant damage to the structure of pike gill lamellae, significant increase (P<0.05) in the activities of antioxidant enzymes (SOD, CAT, GSH-Px), significant increase (P<0.05) in the mRNA expression of pro-apoptotic genes (Bax, Caspase 3), and significant decrease (P<0.05) in the mRNA expression of anti-apoptotic genes (Bcl-2). The mRNA expression of Egln-2 mRNA, a gene encoding prolyl hydroxylase, decreased and then increased, while the mRNA expression of Hif-1a mRNA, a key factor of the hypoxia signalling pathway, increased and then decreased. After reoxygenation, the gill tissue structure and related indexes recovered but did not fully reach the level of the control group.
Conclusion Hypoxic stress significantly altered physiological and biochemical indicators as well as gill lamellae morphology in S. lucioperca, while short-term reoxygenation (6 h) markedly alleviated hypoxic stress responses.Significance This study could provide basic information for further elucidation of the regulatory mechanism of hypoxic stress in S. lucioperca.
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