Morphology and skeletal muscle growth in pirarucu Arapaima gigas Cuvier, 1817 (Teleostei, Arapaimidae)

Abstract

The aim of this work was to evaluate the morphological and growth characteristics of skeletal muscle tissue in pirarucu (Arapaima gigas) using alevins (50 days old) and juveniles (1 year old). Muscle samples were collected from dorsal, lateral cranial and lateral caudal regions, and then frozen in liquid nitrogen. Histological frozen sections (10 μm) were stained with HE and Gomori Trichrome for morphological analysis, and NADH-TR to evaluate muscle fiber oxidative metabolism. Morphometric analysis samples were obtained from dorsal and lateral cranial regions, and the smallest-diameter white fibers were measured. White dorsal muscle was thicker, and two muscle fiber compartments were identified in the lateral cranial region: red (superficial) and white (deep) muscle. Hyperplasia muscle growth predominated in alevins and hypertrophy in juveniles.