Mechanisms of enhanced cardiorespiratory performance under hyperoxia differ with exposure duration in yellowtail kingfish

Hyperoxia has been shown to expand the aerobic capacity of some fishes, although there have been very few studies examining the underlying mechanisms and how they vary across different exposure durations. Here, we investigated cardiorespiratory function of yellowtail kingfish (Seriola lalandi) acutely (~20 hours) and chronically (3-5 weeks) acclimated to hyperoxia (~200 % air saturation). Our results show that aerobic performance of kingfish is limited in normoxia and increases with environmental hyperoxia. Aerobic scope was elevated in both hyperoxia treatments driven by a ~33% increase in maximum O2 uptake (MO2max), although the mechanisms differed across treatments. Fish acutely transferred to hyperoxia primarily elevated tissue O2 extraction, while increased stroke volume-mediated maximum cardiac output was the main driving factor in chronically acclimated fish. Still an improved O2 delivery to the heart in chronic hyperoxia was not the only explanatory factor as such. Here, maximum..., We recorded the rate of whole-animal O2 uptake (MO2) using intermittent-flow respirometry where the % air saturation inside the respirometer was continuously measured using an O2 optode connected to a Firesting O2 system. Automated flush pumps, were set to flush the respirometers for 5 min every 7 min (i.e., 2 min measurement cycles). MO2 was calculated from the slope of the decline in % air saturation between flushes using the following formula: MO2 = (Vr – Vf) × (Δ%Sat/t) × α; where Vr is the volume of the respirometer, Vf is the volume of the fish assuming that 1 g of tissue equals 1 ml of water, Δ%Sat/t is the change in % O2 saturation per time and α is the temperature-, salinity- and atmospheric pressure-dependent solubility coefficient of O2. The first ~30 s of each measurement cycle was excluded from the slope determination to ensure the inclusion of only the linear section of the decline in O2. SMR (standard metabolic rate) was calculated as the mean of the lowest 20% of all MO2..., , # Mechanisms of enhanced cardiorespiratory performance under hyperoxia differ with exposure duration in yellowtail kingfish

[https://doi.org/10.5061/dryad.n2z34tn3v](https://doi.org/10.5061/dryad.n2z34tn3v)

## Description of the data and file structure

The sheet named \"rest, max and scope cardiorespiratory\" contains information on the resting, maximum, and scope cardiorespiratory parameters, i.e., MO2 (SMR, maximum MO2 and aerobic scope, mg O2 h-1), cardiac output (ml min-1), stroke volume (ml), heart rate (beats min-1) and arterial venous O2 content difference (A-VO2, mg O2 ml-1). MO2 stands for O2 uptake and SMR for standard metabolic rate. It also includes, fish ID, weight (g), length (cm), EPOC (excess post-exercise O2 consumption, mg O2), EPOC duration (EPOC duration, h) and EPOC repayment rate (mg O2 h-1), ventricular mass (g), relative ventricular mass (%), relative spleen mass (%), haematocrit (%), haemoglobin concentration (g l-1), MCHC (mean corpuscular haemoglobin concent...

已有研究表明，高氧（hyperoxia）可提升部分鱼类的有氧代谢能力，但目前针对其潜在调控机制，以及该效应随暴露时长差异而变化规律的相关研究仍较为匮乏。本研究针对暴露于约200%空气饱和度高氧环境中的黄条𫚕（Seriola lalandi），分别对其进行急性（约20小时）与慢性（3~5周）驯化处理，以此探究其心肺呼吸功能特征。研究结果显示，黄条𫚕在常氧（normoxia）环境下的有氧代谢能力存在限制，且其有氧表现会随环境高氧水平提升而增强。两种高氧处理组的有氧代谢范围均显著升高，这主要源于最大摄氧量（MO2max）提升约33%，但不同处理组的调控机制存在差异。急性转移至高氧环境的黄条𫚕，主要通过提升组织摄氧效率来实现代谢能力增强；而慢性驯化组的核心调控机制则是每搏输出量介导的最大心输出量提升。不过，慢性高氧环境下心脏氧输送能力的改善，并非该效应的唯一解释因素。本研究中，我们采用间歇式流动呼吸代谢仪（intermittent-flow respirometry）记录全鱼的摄氧速率（MO2）；呼吸代谢箱内的空气饱和度百分比通过连接至Firesting O2系统的氧气光学传感器（O2 optode）进行连续监测。自动冲洗泵设置为每7分钟冲洗呼吸代谢箱5分钟（即采用2分钟的测量周期）。MO2通过两次冲洗之间空气饱和度百分比的下降斜率计算得出，计算公式如下：MO2 = (Vr – Vf) × (Δ%Sat/t) × α；其中Vr为呼吸代谢箱体积，Vf为鱼体体积（假设1克组织对应1毫升水），Δ%Sat/t为单位时间内氧气饱和度百分比的变化量，α为受温度、盐度与大气压力影响的氧气溶解系数。每个测量周期的前约30秒数据被排除在斜率计算之外，以确保仅纳入氧气浓度下降的线性阶段。标准代谢率（SMR, standard metabolic rate）通过所有MO2值中最低的20%的平均值计算得到……
# 高氧暴露下黄条𫚕心肺呼吸功能增强的调控机制随暴露时长而异
[https://doi.org/10.5061/dryad.n2z34tn3v]

## 数据与文件结构说明
名为"rest, max and scope cardiorespiratory"的工作表包含静息、最大及代谢范围心肺呼吸相关参数，具体包括：摄氧速率（MO2，涵盖标准代谢率SMR、最大MO2及有氧代谢范围，单位：mg O2 h⁻¹）、心输出量（单位：ml min⁻¹）、每搏输出量（单位：ml）、心率（单位：次 min⁻¹）以及动静脉血氧含量差（A-VO2，单位：mg O2 ml⁻¹）。其中MO2代表摄氧量，SMR代表标准代谢率。该工作表同时收录了鱼编号、体重（g）、体长（cm）、运动后过量氧耗（EPOC, excess post-exercise O2 consumption，单位：mg O2）、EPOC持续时长（单位：h）、EPOC偿还速率（单位：mg O2 h⁻¹）、心室重量（g）、相对心室质量（%）、相对脾脏质量（%）、红细胞比容（haematocrit，%）、血红蛋白浓度（haemoglobin concentration，单位：g l⁻¹）以及平均红细胞血红蛋白浓度（MCHC, mean corpuscular haemoglobin concent……