De Boeck Gudrun, Lardon Isabelle, Eyckmans Marleen, Vu Trung Nghia, Laukens Kris, Dommisse Roger, Wood Chris M
ECOSPHERE, Department of Biology, University of Antwerp, Groenenborgerlaaan 171, 2020 Antwerp, Belgium.
Bamfield Marine Sciences Centre, 100 Pachena Rd, Bamfield BC V0R 1B0, Canada.
Conserv Physiol. 2024 Aug 13;12(1):coae054. doi: 10.1093/conphys/coae054. eCollection 2024.
Pacific spiny dogfish, , move to shallow coastal waters during critical reproductive life stages and are thus at risk of encountering hypoxic events which occur more frequently in these areas. For effective conservation management, we need to fully understand the consequences of hypoxia on marine key species such as elasmobranchs. Because of their benthic life style, we hypothesized that are hypoxia tolerant and able to efficiently regulate oxygen consumption, and that anaerobic metabolism is supported by a broad range of metabolites including ketones, fatty acids and amino acids. Therefore, we studied oxygen consumption rates, ventilation frequency and amplitude, blood gasses, acid-base regulation, and changes in plasma and tissue metabolites during progressive hypoxia. Our results show that critical oxygen levels ( ) where oxyregulation is lost were indeed low (18.1% air saturation or 28.5 Torr at 13°C). However, many dogfish behaved as oxyconformers rather than oxyregulators. Arterial blood PO levels mostly decreased linearly with decreasing environmental PO. Blood gases and acid-base status were dependent on open versus closed respirometry but in both set-ups ventilation frequency increased. Hypoxia below P resulted in an up-regulation of anaerobic glycolysis, as evidenced by increased lactate levels in all tissues except brain. Elasmobranchs typically rely on ketone bodies as oxidative substrates, and decreased concentrations of acetoacetate and β-hydroxybutyrate were observed in white muscle of hypoxic and/or recovering fish. Furthermore, reductions in isoleucine, glutamate, glutamine and other amino acids were observed. After 6 hours of normoxic recovery, changes persisted and only lactate returned to normal in most tissues. This emphasizes the importance of using suitable bioindicators adjusted to preferred metabolic pathways of the target species in conservation physiology. We conclude that Pacific spiny dogfish can tolerate severe transient hypoxic events, but recovery is slow and negative impacts can be expected when hypoxia persists.
太平洋刺鲨在关键的繁殖生命阶段会迁移到沿海浅水区，因此有遭遇这些区域更频繁发生的低氧事件的风险。为了进行有效的保护管理，我们需要充分了解低氧对诸如板鳃亚纲鱼类等海洋关键物种的影响。由于它们的底栖生活方式，我们假设太平洋刺鲨耐低氧且能够有效调节氧气消耗，并且无氧代谢由包括酮、脂肪酸和氨基酸在内的多种代谢物支持。因此，我们研究了渐进性低氧过程中的氧气消耗率、呼吸频率和幅度、血液气体、酸碱调节以及血浆和组织代谢物的变化。我们的结果表明，失去氧调节能力时的临界氧水平（ ）确实很低（13°C时为空气饱和度的18.1%或28.5托）。然而，许多刺鲨表现为氧顺应者而非氧调节者。动脉血PO水平大多随环境PO的降低而呈线性下降。血液气体和酸碱状态取决于开放式与封闭式呼吸测定法，但在两种设置中呼吸频率均增加。低于P的低氧导致无氧糖酵解上调，除大脑外所有组织中的乳酸水平升高证明了这一点。板鳃亚纲鱼类通常依赖酮体作为氧化底物，在低氧和/或恢复中的鱼类的白色肌肉中观察到乙酰乙酸和β-羟基丁酸的浓度降低。此外，还观察到异亮氨酸、谷氨酸、谷氨酰胺和其他氨基酸的减少。在常氧恢复6小时后，变化仍然存在，大多数组织中只有乳酸恢复正常。这强调了在保护生理学中使用适合目标物种首选代谢途径的合适生物指标的重要性。我们得出结论，太平洋刺鲨能够耐受严重的短暂低氧事件，但恢复缓慢，当低氧持续时可能会产生负面影响。
