Histological Study of Digestive System of Common Carp, Cyprinus carpio Var. Sazan during Early Developmental Stages

This study was aimed to evaluate the development of the digestive system in common carp (Cyprinus carpio) var. Sazan, as a commercially valuable species of the Caspian Sea from hatching up to 55 days post hatching (DPH) based on parifinized histological technique and hematoxylin-eosin staining method. The results showed that moth opening, appearance of pancreas on 2 DPH, epithelial layers of the buccal cavity and esophagus along with their Goblet cells on 3 DPH, rectum on 8 DPH and coiled intestine on 12-13 DPH were occurred. In addition, according to morphological and histological characteristics, the early development of the digestive system in common carp var. Sazan can be divided into three main stages: (1) from hatching up to 3 DPH that is coincide with mouth opening and is readiness of the digestive tract to receive food, (2) up to 8 DPH, is a transitional stage from endogenous toward exogenous feeding that digestive system of larvae is developed in terms of structure and function to receive, digest and absorb of food before the absorption of yolk sac, and (3) third stage from 9 DPH that the pancreas is became functional as main characteristic of this stage, and an essential diagnosis feature of transforming the larvae to young fish. Development of the digestive system in common carp var. Sazan during early stages was similar to other bony fishes with differences in oncogenic and function times.