Rome L C, Funke R P, Alexander R M
Department of Biology, Leidy Laboratories, University of Pennsylvania, Philadelphia 19104.
J Exp Biol. 1990 Nov;154:163-78. doi: 10.1242/jeb.154.1.163.
The aim of this study was to evaluate how fish locomote at different muscle temperatures. Sarcomere length excursion and muscle shortening velocity, V, were determined from high-speed motion pictures of carp, Cyprinus carpio (11-14 cm), swimming steadily at various sustained speeds at 10, 15 and 20 degrees C. In the middle and posterior regions of the carp, sarcomeres of the lateral red muscle underwent cyclical excursions of 0.31 microns, centered around the resting length of 2.06 microns (i.e. from 1.91 to 2.22 microns). The amplitudes of the sarcomere length excursions were essentially independent of swimming speed and temperature. As tail-beat frequency increased linearly with swimming speed regardless of temperature, the sarcomeres underwent the same length changes in a shorter time. Thus, V increased in a linear and temperature-independent manner with swimming speed. Neither temperature nor swimming speed had an influence on tail-beat amplitude or tail height. Our findings indicate that muscle fibres are used only over a narrow, temperature-independent range of V/Vmax (0.17-0.36) where power and efficiency are maximal. Carp start to recruit their white muscles at swimming speeds where the red muscle V/Vmax becomes too high (and thus power output declines). When the V/Vmax of the active muscle falls too low during steady swimming, carp switch to 'burst-and-coast' swimming, apparently to keep V/Vmax high. Because Vmax (maximum velocity of shortening) of carp red muscle has a Q10 of 1.63, the transition speeds between swimming styles are lower at lower temperatures. Thus, carp recruit their white anaerobic muscle at a lower swimming speed at lower temperatures (verified by electromyography), resulting in a lower maximum sustainable swimming speed. The present findings also indicate that, to generate the same total force and power to swim at a given speed, carp at 10 degrees C must recruit about 50% greater fibre cross-sectional area than they do at 20 degrees C.
本研究的目的是评估鱼类在不同肌肉温度下的运动方式。通过对鲤鱼（鲤科鲤属，体长11 - 14厘米）在10℃、15℃和20℃下以各种稳定速度持续游泳的高速运动图像进行分析，确定了肌节长度变化和肌肉缩短速度V。在鲤鱼的中部和后部区域，外侧红色肌肉的肌节进行周期性变化，变化幅度为0.31微米，以2.06微米的静息长度为中心（即从1.91微米到2.22微米）。肌节长度变化的幅度基本上与游泳速度和温度无关。由于尾鳍摆动频率随游泳速度线性增加，与温度无关，因此肌节在更短的时间内经历相同的长度变化。因此，V随游泳速度呈线性且与温度无关的方式增加。温度和游泳速度对尾鳍摆动幅度或尾鳍高度均无影响。我们的研究结果表明，肌肉纤维仅在V/Vmax的一个狭窄的、与温度无关的范围内使用（0.17 - 0.36），在此范围内功率和效率最大。当红色肌肉的V/Vmax变得过高（从而功率输出下降）时，鲤鱼开始在游泳速度增加时募集白色肌肉。在稳定游泳过程中，当活跃肌肉的V/Vmax降得过低时，鲤鱼会切换到“爆发 - 滑行”游泳方式，显然是为了保持V/Vmax较高。由于鲤鱼红色肌肉的Vmax（最大缩短速度）的Q10值为1.63，在较低温度下，游泳方式之间的转换速度更低。因此，在较低温度下，鲤鱼以较低的游泳速度募集白色无氧肌肉（通过肌电图证实），导致最大可持续游泳速度较低。目前的研究结果还表明，为了在给定速度下产生相同的总力和功率来游泳，10℃的鲤鱼必须比20℃的鲤鱼募集约50%更大的纤维横截面积。
