2. Lecturer of Comparitive Anatomy of Vertebrates, Zoology department, Faculty of science, Tanta university, Egypt.
This study aims to illustrate the morphological, histological and ultrastructural differences in the stomach of a carnivorous fish, Clarias gariepinus and an herbivorous fish Oreochromis niloticus in correlation with their feeding habits .Twenty live O. niloticus and C. gariepinus were collected from Nile River. After capture, they were capitated; the entire digestive tract was removed from the body. The stomach was separated and then cut into three parts; the cardiac region was separated and examined. The histological characterizations revealed that the wall of the stomach in both species is composed of four layers. The tunica mucosa of O. niloticusis was thrown up into several broad folds which is lined with high columnar mucous-secreting cells with homogenous faintly stained cytoplasm and basal oval nuclei, large mucous glands were noticed and gastric pits appeared short and shallow in depth while the mucosa layer of C. gariepinus characterized by absence of mucous glands among its epithelial cells and gastric pit is deep and wide .The muscularis layer is thicker in C. gariepinus compared to O. niloticus. TEM of the mucosa layer of the stomach of both species revealed that oxyntic cell that exhibits tubulovesicular system with microvilli and mucous neck cells with extensive masses of mucous secretions, entero-endocrine cells that characterized by electron dense granules .Finally we concluded that there are differences between two studied species according to their feeding habits.
Keywords: Histology- TEM- Oreochromis niloticus- Clarias gariepinus