The purpose of the present study was to investigate the morphology, histochemistry and ultrastructure of the stomach of African Catfish Clarias gariepinus. Grossly, the stomach was J-shaped sac divided into cardiac, fundic and pyloric portions. Histologically, the wall of the stomach composed of four distinct tunics; mucosa, submucosa, muscularis externa and serosa.
The mucosa of the three portions showed thick longitudinal folds lined with simple high columnar cells containing oval basally located nuclei. These columnar cells contained apically located mucosubstances that reacted positively with Periodic Acid Schiff (PAS) and negatively with Alcian-Blue (AB) stains. Many gastric pits were formed by invaginations of
the mucosal layer. Both cardiac and fundic regions contained mucosal glands while the pyloric did not. The fundic glands lined with one cell type; oxynticopeptic cells. Enteroendocrine cells were distributed all over the gastric wall within the epithelial cells lining the gastric mucosa and glands. The lamina propria composed of extensive collagen fibers, many blood vessels and nerves. Strands of smooth muscle fibers separated the lamina propria from the submucosa forming lamina muscularis mucosa. Loose connective tissue was the main component of the tunica submucosa. The pyloric portion had the thickest musclosa that composed of three layers; thin inner and outer longitudinal and thick middle circular layers of SMF. A thin layer of loose connective tissue containing many blood vessels covered by a single layer of mesothelial cells constituting the serosal coat of the stomach. Based on the obtained results in the current study, we concluded that African Catfish Clarias gariepinus possessed a stomach resembles that of a carnivorous nutritious habits.