A Comparative Study of Fibre Type Characteristics and Terminal Innervation in Head and Axial Muscle of the Carp (Cyprinus Carpio L.) : a Histochemical and Electron-Microscopical Study

Abstract

In the axial muscles and in a head muscle (m. hyohyoideus) of the carp two slow (red) and three fast (white, large pink and small pink) fibre types were distinguished on the basis of reactions with antisera, the pH stability of ATPase and succinatedehydrogenase activity. The gradual transition in histochemical characteristics between small and large pink fibres and the occurrence of stadia intermediate between myosatellite cells and small muscle fibres suggest that the small fibres are a growth stage. Density of nerve terminations was highest on red fibres, which is in accordance with physiological data. White axial muscle fibres had the lowest termination density. Pink fibres of the m. hyohyoideus had significantly more terminations per millimeter fibre length than pink fibres of the axial muscles. Vesicle densities per endplate profile and per synaptic contact were similar in all types. Endplates on white fibres had narrower synaptic clefts and vesicles that were slightly more elliptical than those on other types. The presence of swollen mitochondria in endplates on red head muscle fibres may reflect the continuous rhytmic activity of these fibres. The absence of subjunctional folds on slow as well as on fast fibres suggest that endplates on both types release but little acetylcholine per stimulus.