Analysis of the skin of three fish species: Histology, morphometry and resistance tests

Abstract

This study was carried out to analyse the skin of three species of fish (piavuçu Leporinus macrocephalus, pacu prata Mylossoma sp e piraputanga Brycon hilarii) through histological and morphometrical analysis and resistance tests after hardening. Skin samples from the dorsal region were taken and fixed in Bouin solution for 24 hours. They were embedded in paraffin, cut 5 μm thick and stained by Hematoxylin-eosin technique. The cuts were analyzed by light microscopy. A EMIC dynamometer was used for the physical mechanical analysis of the skin in 10 samples, longitudinally oriented from the dorsal region of each specie of fish. The dermis of those fishes has a structural pattern common to teleosts, but the setting and distribution of collagen fibers was different among the analyzed species. The skin dermis thickness differed among the three species by the morphometrical analysis. No difference was observed for the resistance test to traction in piraputanga leather (16.88 N/mm2) as well as in piavuçu leather (18.50 N/mm2). The results for the skin of both fish species were higher than those for pacu (11.83 N/mm2). The value of stretching as to the point of rupture was higher for piavuçu (52.83%) and piraputanga (60.45%), showing no difference among them, but it was lower for pacu (33.83%). The progressive tearing was greater in pacu skin (36.51 N/mm). The skin of the three analyzed species can be turned into leather for the manufacture of several artifacts.