Coughlin D J, Zhang G, Rome L C
University of Pennsylvania, Department of Biology, Leidy Laboratory, Philadelphia 19104, USA.
J Exp Biol. 1996 Dec;199(Pt 12):2703-12. doi: 10.1242/jeb.199.12.2703.
Although the contribution of red muscle to sustained swimming in fish has been studied in detail in recent years, the role of pink myotomal muscle has not received attention. Pink myotomal muscle in the scup (Stenotomus chrysops) lies just medial to red muscle, has the same longitudinal fibre orientation and is recruited along with the red muscle during steady sustainable swimming. However, pink muscle has significantly faster rates of relaxation, and the maximum velocity of shortening of pink muscle (7.26 +/- 0.18 muscle lengths s-1, N = 9, at 20 degrees C, and 4.46 +/- 0.15 muscle lengths s-1, N = 6, at 10 degrees C; mean +/- S.E.M.) is significantly faster than that of red muscle. These properties facilitate higher mass-specific maximum oscillatory power production relative to that of red muscle at frequencies similar to the tailbeat frequency at maximum sustained swimming speeds in scup. Additionally, pink muscle is found in anatomical positions in which red muscle is produces very little power during swimming: the anterior region of the fish, which undergoes the lowest strain during swimming. Pink muscle produces more oscillatory power than red muscle under low-strain conditions (+/- 2-3%) and this may allow pink muscle to supplement the relatively low power generated by red muscle in the anterior regions of swimming scup.
尽管近年来已经对红色肌肉在鱼类持续游泳中的作用进行了详细研究，但粉色肌节肌的作用尚未受到关注。鲷鱼（Stenotomus chrysops）的粉色肌节肌位于红色肌肉的内侧，具有相同的纵向纤维方向，并且在稳定的持续游泳过程中与红色肌肉一起被募集。然而，粉色肌肉的松弛速度明显更快，并且粉色肌肉的最大缩短速度（20℃时为7.26±0.18肌长每秒，N = 9；10℃时为4.46±0.15肌长每秒，N = 6；平均值±标准误）明显快于红色肌肉。相对于红色肌肉，这些特性有助于在与鲷鱼最大持续游泳速度时的尾鳍摆动频率相似的频率下产生更高的质量比最大振荡功率。此外，粉色肌肉所在的解剖位置，红色肌肉在游泳时产生的功率非常小：鱼的前部区域，在游泳时受到的应变最小。在低应变条件下（±2 - 3%），粉色肌肉产生的振荡功率比红色肌肉更多，这可能使粉色肌肉能够补充鲷鱼游泳前部区域红色肌肉产生的相对较低的功率。
