Local differences in myotendinous junctions in axial muscle fibres of carp (Cyprinus carpio L.)

Abstract

We studied the myotendinous junctions of anterior and posterior red and white axial muscle fibres of carp using stereology. In posterior axial muscle fibres of swimming fish, stress (load on the myotendinous junction) must be higher than in anterior fibres as posterior fibres have a longer phase of eccentric activity. As we expected the magnitude of the load on the junction to be reflected in its structure, we compared the interfacial ratio, the ratio between the area of the junctional sarcolemma and the cross-sectional fibre area, of these muscle fibres. This ratio differed significantly between the investigated groups, with red fibres and posterior fibres having the larger ratios. The higher interfacial ratio of posterior myotendinous junctions is in accordance with the proposition mentioned above. The difference between myotendinous junctions of red and white fibres is probably related to a difference in the duration of the load on the junction.