Histological, histochemical and ultrastructural study of the intestine of rainbow trout (Oncorhynchus mykiss).

Abstract: The histological and histochemical characteristics of the intestine and the ultrastructure of it's mucosa were studied in rainbow trout. The histological characterizations revealed that the wall of the intestine is composed of the tunica mucosa, tunica submucosa, tunica muscularis and tunica serosa. Intestinal mucosa displays many villi and a simple columnar epithelium in associated with goblet cells and intraepithelial lymphocytes. Muscularis mucosae and mucosal tubular glands were not seen. Eosinophilic granular cells (mast cells) observed along the intestine mainly beneath the stratum compactum, an acidophilic longitudinal layer. Histochemical analysis showed that the goblet cells have acidic and neutral mucosubstances. At the ultrastructural level, the columnar cells of the intestine have microvilli toward the lumen and are joined together at the apical surfaces by the junctional complexes. Lysosomes, rough endoplasmic reticulum and polymorphic mitochondria are scattered in the supranuclear cytoplasm of enterocytes. Many pinocytotic vesicles were observed in the enterocytes of the middle part of the intestine. Key words: Histology • histochemistry • ultrastructure • intestine • rainbow trout