Morphological and morphometric analysis of skeletal muscle between male and female young adult Colossoma macropomum (Characiformes: Serrasalmidae)

Abstract

This study aimed to evaluate muscle organization in tambaqui in order to describe the muscle growth process. We analyzed the morphometric pattern of fibers from white muscle of young-adults (300 days) by smaller diameter. The organization of white muscle exhibited a typical morphological pattern found in other fish species. Heavier animals showed higher frequency of larger diameter fibers (>50 fim) and smaller animals had higher frequency of smaller diameter fibers (<20 fim) (P=0.005). However, both animals showed the same frequency of intermediate diameter fibers (20-50 fm). Body weight showed a positive correlation with muscle diameter fiber (r=0.45), being 20-50 fim the diameters that contributed the most to animal weight (P <0.0001). A weak correlation between fiber diameter and animal sex was observed (r=0.2). Females showed higher frequency of large fiber diameters (>50 fm) than males. However, there was no difference between body weight and sex (P=0.8). Our results suggest that muscle growth is by hypertrophy and hyperplasia due to a mosaic appearance from different diameters fibers, which is characteristic of large size fish species.