ニシン仔稚魚の体側筋の発達と遊泳速度の変化

Abstract

A morphometric analysis was made of myotomal musculature, together with the measure-ment of the burst swimming speeds in Pacific herring larvae and juveniles. The frequency distribution of white muscle diameter showed that mean fiber diameter increased gradually with development but new small fibers, clearly differing from primitive fibers, were added from about 20mm SL (standard length) to 30mm SL. The diameters of red muscle fibers, however, rather continuously increased with development. The logarithmic plots of cross-sectioned area of white and red muscle against the standard length showed that both relationships in white and red muscle had two regression lines with one inflection point at 30.4mm SL and at 20.1mm SL, re-spectively. The relationships between log estimated fiber numbers of red muscle against log SL had also two regression lines with one inflection point at 24.1mm, whereas those in white muscle had two inflection point at 15.4mm and at 26.9mm. Swimming speed increased exponentially with development, but the relation between log swimming speed (V) and log standard length (L) differed from about 28mm SL (p<0.005):V=0.63L exp (1.04) and V=1.55L exp (0.90). The length in 28mm SL was fit for the changes of morphometry mentioned above in white muscle. This suggested that the maximum swimming speed may be correlated with the development of myotomal musculature, at least in the white muscle.