M. Zakeri Nasab - Department of Marine Biology, Faculty of Natural Resources and Environment, Science and Research Branch, Islamic Azad University, Tehran, Iran
Sh. Jamili - Iranian Fisheries Sciences ResearchInstitute, Agricultural Research,Education and Extension Organization, Tehran, Iran
A.R. Valipour - Inland Waters Aquaculture Research Center, Iranian Fisheries SciencesResearch Institute, Agricultural Research,Education and Extension Organization (AREEO), Bandar Anzali, Iran
S.M.R. Fatemi - Department of Marine Biology, Faculty of Natural Resources and Environment, Science and Research Branch, Islamic Azad University, Tehran, Iran
E. Ramezani Fard - Department of Marine Biology, Faculty of Natural Resources and Environment, Science and Research Branch, Islamic Azad University, Tehran, Iran

The growth of the gastrointestinal tract of the larvae and juvenile of Alburnus chalcoides was studied after histological analysis using light microscopy, haematoxylin-eosin staining and the mouth development was scanned via electron microscopy. This study focuses on the morphology and histology of the mouth growth and digestive tract of A. chalcoides larvae to test the best weaning time for providing practical diet for fry based on the grade of their morphological aspects. It was observed that on the fifth day after hatching, the larvae mouth was opened. On the eighth day, the yolk sac was absorbed by two-thirds. On the same day, food is fed manually. Yolk sac was completely absorbed in ۱۰th day. The histological base of the esophagus was formed by day ۳. At day ۳, the formation of enterocytes started. Also, the larvae hepatopancreas was formed on ۵th day. According to the results, it was observed that after ۸ days onwards, larvae of these fish can have a proper diet. At this day, the size of the mouth was ۸۴ µm. when the lips were formed within ۲۰ days and for the mouth angles ۴۵ºand ۹۰º, the food size for mouth, was ۱۶۸ and ۳۰۷ μm, respectively.

Alburnus chalcoides, Ontogenetic, Digestive system, Larvae, Juvenile