As Earth’s temperature continues to rise, sudden warming events, designated as marine heatwaves (MHWs), are becoming more frequent and longer. This phenomenon is already shown to significantly impact marine ecosystems and respective fauna. While experimental acclimation to higher temperatures is known to affect predatory behavior, metabolism and overall fitness of sharks, the effects of short-term exposure to high temperatures on sharks’ physiology has yet to be investigated in a MHW context. Thus, the aim of our work was to study the impact of a category II MHW (Δ3 °C, 15 days) on: i) hematological parameters (total erythrocytes, leukocytes, thrombocytes, erythrocyte nuclear abnormalities (ENAs) counts, and nucleus to cytoplasmic ratio), ii) heart and spleen to body ratios, and iii) ventilation rates of juvenile catsharks (Scyliorhinus canicula). We found that MHW exposure led to significant changes in normal blood cell counts, by lowering erythrocyte counts and nucleus to cytoplasm ratio, and increasing leukocyte and thrombocyte counts. Moreover, ventilation rates increased consistently over the course of the MHW. However, there were no changes regarding the presence of ENA, as well as spleen and heart to body ratios. Our findings indicate limited capabilities for coping with sudden warming events, suggesting potential disruption in shark physiological homeostasis as the frequency, duration and intensity of MHWs are expected to be strengthened.

随着地球温度的持续升高，被称为海洋热波（MHW）的突然变暖事件变得越来越频繁，持续时间越来越长。已经表明，这种现象会严重影响海洋生态系统和相应的动物群。虽然已知实验适应高温会影响鲨鱼的掠食行为，新陈代谢和整体适应性，但短期暴露在高温下对鲨鱼生理的影响尚需在MHW环境中进行研究。因此，我们的工作目的是研究II类MHW（Δ3°C，15天）对以下方面的影响：i）血液学参数（总红细胞，白细胞，血小板，红细胞核异常（ENA）计数以及对ii）心脏和脾脏与身体的比例，以及iii）幼年猫鲨的通风率（Scyliorhinus canicula）。我们发现，MHW暴露通过降低红细胞计数和细胞核与细胞质的比率，以及增加白细胞和血小板计数，导致正常血细胞计数发生显着变化。此外，在MHW过程中，通风率持续增加。但是，ENA的存在以及脾脏和心脏与身体的比例没有变化。我们的研究结果表明，应对突然变暖事件的能力有限，表明鲨鱼的生理动态平衡可能会受到破坏，因为预计MHW的频率，持续时间和强度将得到加强。