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Fig. 3. Fiber-type composition in the muscles of Weddell seals. (A-C)
Representative sections from metachromatic ATPase-stained muscle samples from
(A) M. longissimus dorsi (swimming muscle), (B) M. pectoralis (non-swimming
muscle) and (C) hindlimb (swimming muscle). I, Type I (slow oxidative) fibers;
IIA, Type IIA (fast-twitch oxidative) fibers; Type IIB (fast-twitch
glycolytic) fibers are completely absent. (D-F) Representative sections of
specific immunohistochemical staining of the M. longissimus dorsi for the
different fiber types. Darkly stained fibers are positive for: (D) Type I
myosin (slow oxidative) and (E) Type IIA myosin (fast-twitch oxidative). (F)
Type IIB myosin (fast-twitch glycolytic) are completely absent.