Atmospheric CO₂ levels have been rising due to an increase in anthropic activities and its implications over marine ecosystems are unprecedented. The present study focused on the effects of ocean acidification (OA) on key hematological parameters of the juvenile small‐spotted catsharks (Scyliorhinus canicula). Eggs were reared throughout the entire embryogenesis (~4 months) plus 5 additional months, in two experimental treatments (control: pCO₂ ~ 400 μatm; and high CO₂: pCO₂ ~ 900 μatm, Δ −0.3 pH units). After blood collection, the following hematological parameters were evaluated: (a) normal blood cells count (erythrocytes, leukocytes, and thrombocytes), (b) presence of erythrocytes with nuclear abnormalities, and (c) erythrocyte nucleus to cytoplasmic ratio. Concomitantly, to determine the cardiac and hematopoietic conditions, the spleen and heart to body ratios were also assessed. The present findings indicate that the measured variables may not be affected by elevated pCO₂ in this temperate species, as no significant differences were observed between treatments across all the endpoints tested. Nonetheless, it is worth mentioning a decreasing trend observed in a number of thrombocytes associated with OA, which should foster further investigation, regarding other aspects of their coagulation response. Along with OA, other stressors are expected to impact marine life, such as warming and hypoxia. Thus, future research should aim to investigate the cumulative effect of these stressors on hematological parameters in sharks.

中文翻译：

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二氧化碳浓度升高对温带猫鲨血液学参数的影响。

由于人类活动的增加，大气中的CO ₂水平一直在上升，其对海洋生态系统的影响是前所未有的。本研究的重点是海洋酸化（OA）对幼小斑纹树鲨（Scyliorhinus canicula）关键血液学参数的影响。卵在整个胚胎（约4个月）加上额外5个月饲养在两个实验性治疗（对照：p CO ₂  〜400μatm;以及高CO ₂：p CO ₂ 〜900μatm，Δ-0.3 pH单位）。采血后，评估以下血液学参数：（a）正常血细胞计数（红细胞，白细胞和血小板），（b）存在核异常的红细胞，以及（c）红细胞核与细胞质的比率。同时，为了确定心脏和造血条件，还评估了脾脏和心脏与身体的比率。目前的发现表明，测得的变量可能不受p CO ₂升高的影响。在这种温带物种中，由于在所有测试终点之间的处理之间未观察到显着差异。尽管如此，值得一提的是，与OA相关的许多血小板中观察到了下降的趋势，这应促进对其凝血反应其他方面的进一步研究。与OA一起，预计其他压力因素也会影响海洋生物，例如变暖和缺氧。因此，未来的研究应旨在调查这些压力源对鲨鱼血液学参数的累积影响。