Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950, USA; Centre for Sustainable Aquatic Ecosystems, Harry Butler Institute, Murdoch University, 90 South Street, Murdoch, Western Australia 6150, Australia.
Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950, USA.
Comp Biochem Physiol A Mol Integr Physiol. 2019 May;231:131-139. doi: 10.1016/j.cbpa.2019.01.025. Epub 2019 Feb 5.
Bluefin tunas are highly specialized fish with unique hydrodynamic designs and physiological traits. In this study, we present results in a captive population that demonstrate strong effects of ambient temperature on the tail beat frequency and swimming speed of a pelagic fish in both pre- and post-prandial states. We measured the responses of a ram ventilator, the Pacific bluefin tuna (Thunnus orientalis), after digestion of a meal to explore the impacts of the metabolic costs of digestion on behavior and respiration. A combination of respirometry, physiological biologging of visceral temperatures, and activity monitoring with accelerometry were used to explore the metabolic costs of digestion and the impacts on ventilation and swimming speed. Experiments were conducted at temperatures that are within the metabolic optimum for Pacific bluefin tuna (17 °C), and at a second temperature corresponding to the upper distributional limit of the species in the California Current (24 °C). Warmer temperatures resulted in higher tail-beat frequency and greater elevation of body temperature in pre-prandial Pacific bluefin tuna. Specific dynamic action (SDA) events resulted in a significant postprandial increase in tail-beat frequency of ~0.2 Hz, compared to pre-prandial levels of 1.5 Hz (17 °C) and 1.75 Hz (24 °C), possibly resulting from ventilatory requirements. Data of fish exercised in a swim-tunnel respirometer suggest that the observed increase in tail-beat frequency comprise 5.5 and 6.8% of the oxygen demand during peak SDA at 24 °C and 17 °C respectively. The facultative increase in swimming speed might increase oxygen uptake at the gills to meet the increasing demand by visceral organs involved in the digestive process, potentially decreasing the available energy of each meal for other metabolic processes, such as growth, maturation, and reproduction. We hypothesize that these post-prandial behaviors allow tuna to evacuate their guts more quickly, ultimately permitting fish to feed more frequently when prey is available.
蓝鳍金枪鱼是高度特化的鱼类，具有独特的流体力学设计和生理特征。在这项研究中，我们展示了圈养种群的结果，表明环境温度对洄游性鱼类在进食前后的尾拍频率和游泳速度有强烈影响。我们测量了一个 ram 通风机（太平洋蓝鳍金枪鱼）在进食后的反应，以探索消化代谢成本对行为和呼吸的影响。结合呼吸测量、内脏温度的生理生物记录和加速度计的活动监测，我们探索了消化代谢成本及其对通风和游泳速度的影响。实验在代谢最适温度（17°C）和物种在加利福尼亚海流中分布上限对应的第二温度（24°C）下进行。温暖的温度导致进食前的太平洋蓝鳍金枪鱼的尾拍频率更高，体温升高。与 17°C 时的 1.5Hz 和 24°C 时的 1.75Hz 相比，特定动力作用（SDA）事件导致进食后尾拍频率显著增加约 0.2Hz，可能是由于通气需求所致。在游泳隧道呼吸测量仪中运动的鱼的数据表明，在 24°C 和 17°C 时，观察到的尾拍频率增加分别占峰值 SDA 期间耗氧量的 5.5%和 6.8%。游泳速度的兼性增加可能会增加鳃的氧气摄取量，以满足参与消化过程的内脏器官不断增加的需求，这可能会减少每顿饭用于其他代谢过程（如生长、成熟和繁殖）的可用能量。我们假设这些进食后的行为使金枪鱼能够更快地排空肠道，最终使鱼在有猎物时能够更频繁地进食。
