Diving optimality models predict air breathers to routinely dive within aerobic limits, but predator avoidance dives may be an exception. Lengthening submergence times during a predation threat may enhance survival probability, and we therefore hypothesized that predator avoidance dives in juvenile estuarine crocodiles (Crocodylus porosus) would be partially anaerobically fueled. We also predicted that reliance on anaerobic metabolism would increase at elevated temperatures to offset the faster depletion of body oxygen stores. Crocodiles were maintained at 28° and 34°C for 60 d and subsequently underwent simulated predator avoidance dive trials at two test temperatures (28° and 34°C). Blood was sampled immediately on surfacing to measure plasma lactate concentrations relative to nondiving (control) values. Aerobic dive limits (cADL; min) were also calculated using known body mass and oxygen storage relationships and rates of diving oxygen consumption and compared with observed dive durations. Postdive plasma lactate levels were elevated beyond resting levels at both test temperatures, indicating that aerobic thresholds were surpassed during simulated predator avoidance dives. Similarly, ≥90% of dive durations exceeded cADLs at both test temperatures. Postdive plasma lactate concentrations were independent of water temperature and thermal acclimation treatment. Together, these findings suggest that reliance on anaerobiosis during simulated predator avoidance dives is important regardless of temperature.

中文翻译：

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跳水超过有氧极限：在空气呼吸温度中，温度对模拟捕食者避免跳水的厌氧支持的影响。

潜水最优模型预测空气呼吸器通常在有氧极限内潜水，但是避免捕食者潜水可能是一个例外。在捕食威胁期间延长淹没时间可能会提高生存概率，因此我们假设在少年河口鳄（Crocodylus porosus）中避免捕食者的潜水会部分地厌氧燃烧。我们还预测到，在升高的温度下，对厌氧代谢的依赖将增加，以抵消体内氧存储的更快消耗。将鳄鱼在28°C和34°C保持60天，然后在两个测试温度（28°C和34°C）下进行模拟的捕食者躲避潜水试验。立即在表面上采集血样以测量血浆乳酸浓度相对于非潜水（对照）值。有氧潜水极限（cADL; 还使用已知的体重和氧气存储关系以及潜水氧气消耗率来计算最小分钟数），并与观察到的潜水时间进行比较。在两个测试温度下，产后血浆乳酸水平都升高到超过静息水平，这表明在模拟的捕食者回避潜水过程中，有氧阈值已超过。同样，在两种测试温度下，≥90％的潜水时间都超过了cADL。产后血浆乳酸浓度与水温和热适应处理无关。总之，这些发现表明，无论温度如何，在模拟捕食者躲避潜水期间对厌氧菌的依赖都很重要。在两个测试温度下，产后血浆乳酸水平都升高到超过静息水平，这表明在模拟的捕食者回避潜水过程中，有氧阈值已超过。同样，在两种测试温度下，≥90％的潜水时间都超过了cADL。产后血浆乳酸浓度与水温和热适应处理无关。总之，这些发现表明，无论温度如何，在模拟捕食者躲避潜水期间对厌氧菌的依赖都很重要。在两个测试温度下，产后血浆乳酸水平都升高到超过静息水平，这表明在模拟的捕食者回避潜水过程中，有氧阈值已超过。同样，在两种测试温度下，≥90％的潜水时间都超过了cADL。产后血浆乳酸浓度与水温和热适应处理无关。总之，这些发现表明，无论温度如何，在模拟捕食者躲避潜水期间对厌氧菌的依赖都很重要。产后血浆乳酸浓度与水温和热适应处理无关。总之，这些发现表明，无论温度如何，在模拟捕食者躲避潜水期间对厌氧菌的依赖都很重要。产后血浆乳酸浓度与水温和热适应处理无关。总之，这些发现表明，无论温度如何，在模拟捕食者躲避潜水期间对厌氧菌的依赖都很重要。