© 1996 by The Society for Integrative and Comparative Biology
The Roles of Pink and Red Muscle in Powering Steady Swimming in Scup, Stenotomus chrysops1
Science Division, Widener University, One University Place Chester, Pennsylvania 19013
University of Pennsylvania, Department of Biology, Leidy Laboratory Philadelphia, Pennsylvania 19104
Fishes power steady, undulatory swimming using both red and pink muscle. In this study we examined the roles of the two fiber types in generating power for swimming by using two-step technique. First, in vivo data is collected from swimming fish, and second, the electrical activity and muscle length change conditions recorded in vivo are recreated in vitro with isolated muscle bundles. Force production and power generation by muscle during swimming can then be estimated. In scup, both red and pink muscle are recruited to power swimming at the maximum sustained swimming speed. For both fiber types, the duration of electrical activity decreases from anterior to posterior. However, the amplitude of muscle length change increases anterior to posterior. Mass-specific power production increases posteriorly for both muscle types. The faster contraction kinetics of pink muscle translate to higher power production pink muscle relative to red muscle for all longitudinal positions of the fish. Determination of absolute power production, based on mass-specific power and muscle mass, shows that the posterior regions of the fish generate the most power for swimming. At 20°C, red muscle generates more absolute power than pink due to its higher muscle mass. However, at 10°C, pink muscle generates more absolute power than red, because red muscle produces little or no positive power for all longitudinal positions.