The adductor pectoral fin muscle of Micropogonias furnieri (Perciformes: Sciaenidae): a morphological and histochemical study

Abstract

The adductor pectoral fin muscle in post-spawning females of the white croaker Micropogonias furnieri (Desmarest, 1823) was described from the morphological, histochemical and morphometric point of view. A morphological description performed by planes down to the deep layer was done, having found five muscles: superficial, medial, radial and deep adductors, and dorsal arrector. Their fibers were studied applying histochemical techniques: succinic dehydrogenase (SDH) to evidence mitochondria, periodic acid-Schiff (PAS) for glycogen, Sudan black for lipids, myosin adenosinetriphosphatase (mATPase) to evidence fiber types and modified mATPase for capillaries. Fiber diameters were measured and the number of capillaries was counted. Fiber subtypes called small, medium and large were found within red, pink and white fibers, the latter prevailing. A staining homogeneity was observed in white fibers after alkaline pre-incubations. The number of capillaries decreased from red to white fibers. Due to the high prevalence of white fibers, the adductor muscle of the pectoral fins would be related to rapid and discontinuous movements and with the body stabilization during subcarangiform swimming. The white fibers staining homogeneity observed in this research would correspond to the post-spawning gonad stage studied.