Table_1_Non-invasive MRI Studies of Ventilatory and Cardiovascular Performance in Edible Crabs Cancer pagurus During Warming Under Elevated CO2 Levels.docx

The thermal tolerance of marine decapod crustacea is defined through their capacities for oxygen uptake and distribution. High ambient CO2 levels were previously shown to reduce hemolymph oxygen levels at enhanced cardiac performance during warming. This study investigated the impacts of warming under two CO2 levels on ventilation and hemolymph circulation in edible crabs Cancer pagurus. It also highlights changes in the ventilatory and cardiac pauses displayed by Decapoda under routine metabolism. Animals were exposed to step-wise, sub-critical warming (12–20°C over 5 days) under control (470 μatm) and high (1,350 μatm) water PCO2. Flow-through respirometry was combined with magnetic resonance imaging and infra-red photoplethysmography to allow for simultaneous, non-invasive measurements of metabolic rates (M˙O2), ventilation and cardiovascular performance. Crabs spent significantly more time in a low M˙O2 state (metabolic pause), when experiencing high CO2 conditions above 16°C, compared to normocapnic warming. Heart rates leveled off beyond 18°C at any CO2 level. Cardiac output continued to increase with high-CO2-warming, due to elevated cardiac stroke volumes. Consequently, temperature-dependent branchial hemolymph flow remained unaffected by CO2. Instead, a suppressing effect of CO2 on ventilation was found beyond 16°C. These results indicate constrained oxygen uptake at stable cardiovascular performance in a decapod crustacean.
Cancer pagurus: urn:lsid:zoobank.org:act:B750F89A-84B5-448B-8D80-EBD724A1C9D4

海洋十足目甲壳动物的热耐受性由其氧摄取与氧分布能力决定。既往研究表明，在升温过程中，高环境CO₂水平可在增强心脏功能的同时降低血淋巴（hemolymph）氧含量。本研究探究了两种CO₂水平下的升温对食用蟹普通黄道蟹（Cancer pagurus）换气与血淋巴循环的影响，并揭示了十足目动物在常规代谢状态下的换气暂停与心脏停搏变化。
实验动物被置于对照（470 μatm）与高（1350 μatm）水体二氧化碳分压条件下，接受阶梯式亚临界升温（5天内从12℃升至20℃）。本研究将流水式呼吸代谢仪与磁共振成像、红外光体积描记术相结合，实现了代谢率（M˙O2）、换气功能与心血管性能的同步无创测量。
与常碳分压升温组相比，当水温超过16℃且处于高CO₂条件时，螃蟹处于低代谢率状态（代谢暂停）的时间显著更长。在任意CO₂水平下，心率均在18℃以上趋于平稳。由于每搏输出量升高，高CO₂升温组的心输出量仍随温度升高而持续增加。因此，温度依赖性的鳃血淋巴流量并未受CO₂水平影响。相反，当水温超过16℃时，CO₂对换气产生了抑制作用。上述结果表明，十足目甲壳动物在心血管性能稳定的状态下，其氧摄取能力受到限制。
普通黄道蟹（Cancer pagurus）的分类学标识符：urn:lsid:zoobank.org:act:B750F89A-84B5-448B-8D80-EBD724A1C9D4