Korsmeyer K E, Lai N C, Shadwick R E, Graham J B
Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla 92093-0204, USA.
J Exp Biol. 1997 Jul;200(Pt 14):1975-86. doi: 10.1242/jeb.200.14.1975.
Cardiac performance in the yellowfin tuna (Thunnus albacares, 673-2470 g, 33-53 cm fork length, FL) was examined in unanesthetized fish swimming in a large water tunnel. Yellowfin tuna were fitted with either electrocardiogram electrodes or a transcutaneous Doppler blood-flow probe over the ventral aorta and exposed to changes in swimming velocity (range 0.8-2.9 FLs-1) or to an acute change in temperature (18-28 degrees C). Heart rates (fH) at +/-1 degree C (30-130 beats min-1) were lower on average than previous measurements with non-swimming (restrained) tunas and comparable with those for other active teleosts at similar relative swimming velocities. Although highly variable among individuals, fH increased with velocity (U, in FLs-1) in all fish (fH = 17.93U + 49.93, r2 = 0.14, P < 0.0001). Heart rate was rapidly and strongly affected by temperature (Q10 = 2.37). Blood flow measurements revealed a mean increase in relative cardiac output of 13.6 +/- 3.0% with exercise (mean velocities 1.23-2.10 FLs-1) caused by an 18.8 +/- 5.4% increase in fH and a 3.9 +/- 2.3% decrease in stroke volume. These results indicate that, unlike most other fishes, cardiac output in yellowfin tuna is regulated primarily through increases in fH. Acute reductions in ambient temperature at slow swimming velocities resulted in decreases in cardiac output (Q10 = 1.52) and fH (Q10 = 2.16), but increases in stroke volume (Q10 = 0.78). This observation suggests that the lack of an increase in stroke volume during exercise is not due to the tuna heart operating at maximal anatomical limits.
在大型水洞中游泳的未麻醉黄鳍金枪鱼（Thunnus albacares，体重673 - 2470克，叉长33 - 53厘米，FL）的心脏功能得到了研究。黄鳍金枪鱼被安装了心电图电极或腹主动脉上的经皮多普勒血流探头，并暴露于游泳速度变化（范围0.8 - 2.9 FLs-1）或温度急性变化（18 - 28摄氏度）中。在±1摄氏度（30 - 130次/分钟）时的心率（fH）平均低于之前对非游泳（受限）金枪鱼的测量值，并且与其他活跃硬骨鱼在相似相对游泳速度下的心率相当。尽管个体间差异很大，但所有鱼的fH都随速度（U，单位为FLs-1）增加（fH = 17.93U + 49.93，r2 = 0.14，P < 0.0001）。心率受温度影响迅速且强烈（Q10 = 2.37）。血流测量显示，运动（平均速度1.23 - 2.10 FLs-1）导致相对心输出量平均增加13.6 ± 3.0%，这是由fH增加18.8 ± 5.4%和每搏输出量减少3.9 ± 2.3%引起的。这些结果表明，与大多数其他鱼类不同，黄鳍金枪鱼的心输出量主要通过fH的增加来调节。在慢游泳速度下环境温度的急性降低导致心输出量（Q10 = 1.52）和fH（Q10 = 2.16）下降，但每搏输出量增加（Q10 = 0.78）。这一观察结果表明，运动期间每搏输出量没有增加并非由于金枪鱼心脏在最大解剖极限下运作。
