Histological and Cytological Studies on Gastrointestinal Tract of Some Nile Fish Species with Special Reference To ages variations

The present investigation aimed to study the microscopic structure of the alimentary ct of two different fresh water fish species concerning age variation, to throw more lighttheir structure and how such diet changes affect the histological pictureThe study was conducted on 150 apparently healthy of two different fish species varying habitats, carnivorous fish, catfish (Clarias lazera) and herbivorous one, grass. Both species were at different age period as mature and immature (finger lings) of’aried lengthes. The fish species were obtained from Abbasa fish farm at Sharkeia ’hovince, Egypt. The organs examined in both fish species included the esophagus, Itomachtxamined with light microscope. For transmision electron microscopy, the specimens were nxed in 2.5% glutaraldehyde, then post fixed in 2% Osmium tetroxide for 1.5 h, then~repared and examined by electron microscope. The esophagus of carnivorous fish was short with highly branched mucosal folds forming secondary and tertiary folds, it ends on the cardia of the stomach, whereas that of the herbivorous was very short with le