Histological development of the alimentary channel of Caspian Roach (Rutilus rutilus caspicus)

The histology of digestive tract of Caspian roach (Rutilus rutilus caspicus) were studied for 53 days from hatching to fingerling size at the natural habitat of the larval stage. Ages 1، 4، 10، 18، 28، 39 and 53 days after hatching (DAH) were selected for the histological studies. after sampling and fixation with 10 percent formalin the histological process were conduct. The newly hatched larvae showed a simple and undifferentiated digestive tube. The oral cavity was still closed. Tubular shape liver and primary swim bladder was other features of this stage. The larvae at 4 DAH had the mouth opened and a few goblet cells between stratified cells of pharynx and a small esophagus with stratified squamous epithelium were observed. The most important incident at 10 DAH was starting the exogenous feeding. The buds and goblet cells in boccopharingeal cavity were changed position deeper in epithelium. Fully absorption of yolk sac and final differentiation of esophagus happened until 28 DPH. The complete differentiate of pharyngeal teeth، deletion of microscopic observed yolk sac and twisting the intestine were other features until the end of the study. Intestine was the first and the pharyngeal teeth were the last region differentiated. Keeping endogenous feed long time after starting exogenous feed shows a good point in this fish to increase survival in lack of food conditions. The ontogeny features were discussed in this study showed that this organ differentiate same in this fish as other Ostariophisy fish although there are some Interspecies differences like what we saw in pharyngeal teeth.