Dj. Coughlin et Lc. Rome, THE ROLES OF PINK AND RED MUSCLE IN POWERING STEADY SWIMMING IN SCUP,STENOTOMUS CHRYSOPS, American zoologist, 36(6), 1996, pp. 666-677
Fishes power steady, undulatory swimming using both red and pink muscl
e. In this study we examined the roles of the two fiber types in gener
ating power for swimming by using a two-step technique. First, in vice
data is collected from swimming fish, and second, the electrical acti
vity and muscle length change conditions recorded in vivo are recreate
d in vitro with isolated muscle bundles, Force production and power ge
neration by muscle during swimming can then be estimated. In scup, bot
h red and pink muscle are recruited to power swimming at the maximum s
ustained swimming speed. For both fiber types, the duration of electri
cal activity decreases from anterior to posterior. However the amplitu
de of muscle length change increases anterior to posterior. Mass-speci
fic power production increases posteriorly for both muscle types. The
faster contraction kinetics of pink muscle translate to higher power p
roduction by pink muscle relative to red muscle for all longitudinal p
ositions of the fish. Determination of absolute power production based
on mass-specific power and muscle mass, shows that the posterior regi
ons of the fish generate the most power for swimming. At 20 degrees C,
red muscle generates more absolute power than pink due to its higher
muscle mass. However, at 10 degrees C, pink muscle generates more abso
lute power than red, because red muscle produces little or no positive
power for all longitudinal positions.