Bigeye thresher sharks (Alopias superciliosus) and swordfish (Xiphias gladius) are large, pelagic fishes, which make long-duration, diurnal foraging dives from warm, surface waters (18–24 °C) to cold waters beneath the thermocline (5–10 °C). In bigeye thresher sharks, the subcutaneous position of the red, aerobic swimming muscles (RM) suggests that RM temperature mirrors ambient during dives (i.e., ectothermy). In swordfish, the RM is closer to the vertebrae and its associated with vascular counter-current heat exchangers that maintain RM temperature above ambient (i.e., RM endothermy). Here, we sought to determine how exposure to a wide range of ambient temperatures (8, 16, 24 °C) impacted peak power output and optimum cycle (i.e., tailbeat) frequency (0.25, 0.5, 1 Hz) in RM isolated from both species. Bigeye thresher shark RM did not produce substantial power at high cycle frequencies, even at high temperatures; but it did produce relatively high power at slow cycle frequencies regardless of temperature. Swordfish RM produced more power when operating at a combination of fast cycle frequencies and higher temperatures. This suggests that swordfish RM benefits considerably more from warming than bigeye thresher shark RM, while the RM of both species was able to produce power at cold temperatures and slow cycle frequencies. Despite different thermal strategies (i.e., ectothermy vs. RM endothermy), the ability of the RM to power sustained swimming during foraging-related search behaviors may contribute to the unique ability of these fishes to successfully exploit food resources in deep, cold water.

大眼长鼻鲨（Alopias superciliosus）和箭鱼（Xiphias gladius）是大型的远洋鱼类，它们会进行长时间的昼夜觅食，从温暖的地表水（18–24°C）跳至温床以下的冷水（5–10°C）。在大眼长须鲨中，红色的有氧游泳肌（RM）的皮下位置表明，RM的温度在潜水过程中反映了周围环境（即，外吸）。在箭鱼中，RM靠近椎骨，并且与血管逆流热交换器相关联，该热交换器使RM温度保持在环境温度之上（即RM吸热）。在这里，我们试图确定暴露于大范围环境温度（8、16、24°C）如何影响峰值功率输出和最佳RM（0.25、0.5、1 Hz）周期（0.25、0.5、1 Hz），两者隔离种类。大眼脱粒机鲨鱼RM即使在高温下也不会在高循环频率下产生大量功率。但无论温度如何，它在慢速循环频率下确实会产生相对较高的功率。箭鱼RM在快速循环频率和更高温度下运行时可产生更多功率。这表明箭鱼RM从变暖中获得的收益比大眼脱粒器鲨鱼RM显着多，而两个物种的RM都能在低温和慢循环频率下发电。尽管采取了不同的热策略（例如，外吸与RM吸热），RM在觅食相关搜索行为期间为持续游泳提供动力的能力可能有助于这些鱼独特的能力，从而可以成功地利用深冷水中的食物资源。箭鱼RM在快速循环频率和更高温度下运行时可产生更多功率。这表明箭鱼RM从变暖中获得的收益比大眼脱粒器鲨鱼RM显着多，而两个物种的RM都能在低温和慢循环频率下发电。尽管采取了不同的热策略（例如，外吸与RM吸热），RM在觅食相关搜索行为期间为持续游泳提供动力的能力可能有助于这些鱼独特的能力，从而可以成功地利用深冷水中的食物资源。箭鱼RM在快速循环频率和更高温度下运行时可产生更多功率。这表明箭鱼RM从变暖中获得的收益比大眼脱粒器鲨鱼RM显着多，而两个物种的RM都能在低温和慢循环频率下发电。尽管采取了不同的热策略（例如，外吸与RM吸热），RM在觅食相关搜索行为期间为持续游泳提供动力的能力可能有助于这些鱼独特的能力，从而可以成功地利用深冷水中的食物资源。