In aquatic animals, hypoxia is associated with growth retardation, impaired immunity, susceptibility to pathogens, oxidative stress, and mortality. However, the relative long-term effects of hypoxia on bivalves, including abalone, are not well understood. In this study, we examined the effects of exposure to hypoxic (2.5 and 4 mg O₂ L⁻¹) and normoxic (8 mg O₂ L⁻¹) conditions on the growth, survival, and immune and antioxidant responses of the economically important Pacific abalone Haliotis discus hannai over a 4 month period. We observed that exposure to 2.5 mg O₂ L⁻¹ resulted in marked reductions in assessed shell parameters, average meat weight, and survival compared with exposure to 4 and 8 mg O₂ L^–1. There were also significant reductions in oxygen consumption and ammonia-N excretion in abalone exposed to 2.5 mg O₂ L⁻¹. We also detected initial immunosuppression in the 2.5 mg O₂ L⁻¹-treated abalone, as evidenced by a significant reduction in total hemocytes and inhibition of antibacterial and lysozyme activities. Furthermore, intracellular malondialdehyde concentrations were significantly elevated at 1 month in the 2.5 mg O₂ L⁻¹ treatment group, whereas there were reductions in the levels of glutathione and enzymatic activities of catalase and superoxide dismutase, thereby indicating potential hypoxia-induced oxidative stress and a depression of antioxidant capacity. After 4 months of treatment, severe hypoxia (2.5 mg O₂ L⁻¹) had significantly modulated all measured parameters, whereas exposure to 4 and 8 mg O₂ L⁻¹ had induced no significant effects. Collectively, our observations indicate that under long-term exposure to hypoxia, Pacific abalone failed to maintain an effective antioxidant defense system and adequate immunity, with the observed biochemical disruptions leading to a reduction in growth and survival.

在水生动物中，缺氧与生长发育迟缓，免疫力下降，对病原体的敏感性，氧化应激和死亡率有关。然而，对缺氧对包括鲍鱼在内的双壳类动物的相对长期影响尚不清楚。在这项研究中，我们研究了暴露于低氧（2.5和4 mg O ₂ L ^-1）和常氧（8 mg O ₂ L ^-1）条件对经济上重要的生长，存活以及免疫和抗氧化反应的影响太平洋鲍鱼Haliotis discus hannai，历时4个月。我们观察到暴露于2.5 mg O ₂ L ^-1与暴露于4和8 mg O ₂ L ^–1相比，可评估的壳参数，平均肉重和存活率显着降低。暴露于2.5 mg O ₂ L ^-1的鲍鱼的耗氧量和氨氮排泄量也显着降低。我们还检测到2.5 mg O ₂ L ^-1处理的鲍鱼的初始免疫抑制作用，这可通过总血细胞的显着减少以及抑制细菌和溶菌酶活性来证明。此外，在2.5 mg O ₂ L ^-1中，细胞内丙二醛浓度在1个月时显着升高治疗组，谷胱甘肽水平和过氧化氢酶和超氧化物歧化酶的酶活性下降，从而表明潜在的低氧诱导的氧化应激和抗氧化能力下降。治疗4个月后，严重缺氧（2.5 mg O ₂ L ^-1）可以显着调节所有测量参数，而暴露于4和8 mg O ₂ L ^-1则无明显影响。总体而言，我们的观察结果表明，在长期暴露于缺氧条件下，太平洋鲍鱼无法维持有效的抗氧化防御系统和足够的免疫力，并且观察到的生化破坏导致生长和存活率降低。