Clark T D, Seymour R S
Earth and Environmental Sciences, University of Adelaide, South Australia 5005, Australia.
J Exp Biol. 2006 Oct;209(Pt 19):3940-51. doi: 10.1242/jeb.02440.
This study utilizes a swimming respirometer to investigate the effects of exercise and temperature on cardiorespiratory function of an active teleost, the yellowtail kingfish (Seriola lalandi). The standard aerobic metabolic rate (SMR) of S. lalandi (mean body mass 2.1 kg) ranges from 1.55 mg min(-1) kg(-1) at 20 degrees C to 3.31 mg min(-1) kg(-1) at 25 degrees C. This 2.1-fold increase in SMR with temperature is associated with a 1.5-fold increase in heart rate from 77 to 117 beats min(-1), while cardiac stroke volume remains constant at 0.38 ml beat(-1) kg(-1) and the difference in oxygen content between arterial and mixed venous blood [(Ca(O2)-Cv(O2))] increases marginally from 0.06 to 0.08 mg ml(-1). During maximal aerobic exercise (2.3 BL s(-1)) at both temperatures, however, increases in cardiac output are limited to about 1.3-fold, and increases in oxygen consumption rates (up to 10.93 mg min(-1) kg(-1) at 20 degrees C and 13.32 mg min(-1) kg(-1) at 25 degrees C) are mediated primarily through augmentation of (Ca(O2)-Cv(O2)) to 0.29 mg ml(-1) at 20 degrees C and 0.25 mg ml(-1) at 25 degrees C. It seems, therefore, that the heart of S. lalandi routinely works close to its maximum capacity at a given temperature, and changes in aerobic metabolism due to exercise are greatly reliant on high blood oxygen-carrying capacity and (Ca(O2)-Cv(O2)). Gross aerobic cost of transport (GCOT) is 0.06 mg kg(-1) BL(-1) at 20 degrees C and 0.09 mg kg(-1) BL(-1) at 25 degrees C at the optimal swimming velocities (U(opt)) of 1.2 BL s(-1) (opt) and 1.7 BL s(-1), respectively. These values are comparable with those reported for salmon and tuna, implying that the interspecific diversity in locomotor mode (e.g. subcarangiform, carangiform and thunniform) is not concomitant with similar diversity in swimming efficiency. A low GCOT is maintained as swimming velocity increases above U(opt), which may partly result from energy savings associated with the progressive transition from opercular ventilation to ram ventilation.
本研究利用游泳呼吸仪，调查运动和温度对活跃硬骨鱼黄尾鰤（Seriola lalandi）心肺功能的影响。黄尾鰤（平均体重2.1千克）的标准有氧代谢率（SMR）范围为：20℃时为1.55毫克·分钟⁻¹·千克⁻¹，25℃时为3.31毫克·分钟⁻¹·千克⁻¹。随着温度升高，SMR增长2.1倍，心率从77次·分钟⁻¹增加到117次·分钟⁻¹，增长1.5倍，而心搏量保持恒定，为0.38毫升·次⁻¹·千克⁻¹，动脉血与混合静脉血之间的氧含量差值[(Ca(O₂)-Cv(O₂))]从0.06毫克·毫升⁻¹略微增加到0.08毫克·毫升⁻¹。然而，在两个温度下进行最大有氧运动（2.3体长·秒⁻¹）时，心输出量的增加限制在约1.3倍，耗氧率的增加（20℃时高达10.93毫克·分钟⁻¹·千克⁻¹，25℃时为13.32毫克·分钟⁻¹·千克⁻¹）主要是通过将(Ca(O₂)-Cv(O₂))分别提高到20℃时的0.29毫克·毫升⁻¹和25℃时的0.25毫克·毫升⁻¹来实现的。因此，似乎黄尾鰤的心脏在给定温度下通常接近其最大容量工作，运动引起的有氧代谢变化在很大程度上依赖于高血液携氧能力和(Ca(O₂)-Cv(O₂))。在20℃时，最佳游泳速度（U(opt)）为1.2体长·秒⁻¹时，总有氧运输成本（GCOT）为0.06毫克·千克⁻¹·体长⁻¹；在25℃时，最佳游泳速度为1.7体长·秒⁻¹时，GCOT为0.09毫克·千克⁻¹·体长⁻¹。这些值与鲑鱼和金枪鱼报道的值相当，这意味着运动模式的种间差异（例如亚鲹形、鲹形和金枪鱼形）与游泳效率的类似差异并不相关。当游泳速度高于U(opt)时，GCOT保持较低水平，这可能部分是由于与从鳃盖通气逐渐过渡到冲压通气相关的能量节省。
