عنوان مقاله [English]
Histological development of Beluga during life stages (1-75 days post hatching) was studied by using light microscopy. Larvae were fixed in bouin’s solution, then dehydrated and embedded in parrafin wax. Sections of 5-7 μm thick were produced and stained according to standard histological technique: hematoxylin-eosin (HαE). The stomach was undifferentiated and filled with yolk at hatching. Walls of the future stomach were lined by one layer of squamous endodermal epithelium. An oblique furrow of the digestive tube wall started to develop on the dorsal-posterior region of the yolk sac at 3 days after hatching and divided the alimentary canal into two differetiated regions: the future stomach and intermediate intestine. At 7 days after hatching, a non–glandular stomach (pyloric region) with several mucosal folds appeared. The epithelium of the glandular stomach (cardiac region) consisted of simple cuboidal. At 13 days after hatching, the connection between the esophagus and the cardiac stomach took place, at that time several gastric glands were visible in glandular stomach. Pyloric caecum was appeared between non glandular stomach and intermediate intestine at 15 days after hatching, .At onset of exogenous feeding (17-19 days post hatching) yolk sac reserves were not completely depleted from the cardiac stomach and suggesting a period of mixed nutrition.Between 36 and 43 days post hatching the muscular layer thickess of the pyloric stomach dramatically increased. At 57 days after hatching thin connective tissue penetrated into the pyloric caecum and divided it to several lobular portion. At 75 days after hatching a thin layer of smooth muscle appeared around the gastric glands. This information may be useful to improve rearing efficiency of Beluga and the other sturgeons.