Histological description of digestive tract segments of commercially-produced pirarucu (Arapaima gigas)

Abstract

The aim of this study was to histologically characterize portions of the digestive tract (esophagus, stomach, pyloric caeca and intestine) of 10 juvenile pirarucu (Arapaima gigas), with an average weight of 3.45 kg ±0.67, captured at fish farms. Histological processing was performed in line with the methods proposed by the UFPI/CPCE Animal Anatomy Laboratory. The sections were analyzed under a trinocular biological microscope (Nova®). The structural composition of the organs was recorded via photomicrographs, using a five-megapixel digital camera coupled to a microscope, with Toupview® capture software. The muscular layer of the mucosa was not observed in the medial segment of the esophagus. Gastric glands were observed in the medial region of the stomach body, in the lamina propria of the mucosa and tunica muscularis, with considerable thickness. The histological characteristics of the pyloric caeca were similar to those of the first segments of the Pirarucu midgut, with apparent variation in the thickness of the mucosal folds, submucosa and tunica muscularis according to organ diameter. Intestinal fold organization and goblet cell distribution varied along the digestive tract. Histologically, the organs of the Pirarucu digestive tract exhibited characteristics similar to those of other carnivorous teleosts.