مطالعه بافت شناسي مراحل تكوين روده در لارو فيل ماهي (Huso huso)

A histological study of the intestine development of beluga (Huso huso) larvae

Histological development of beluga during life stages (1-75 days post hatch) was studied by using light microscopy. Larvae were fixed in bouinʹs solution then dehydrated and embedded in paraffin wax. Sections of 5-7|im thick were produced and stained according to standard histological techniques: Hematoxylin-Eosin (HaE), and periodic Acid Schiff (PAS). One-day-old larvae possess a primordial intestine, which is lined by a simple columnar ciliated epithelium. 3 days after hatching, an oblique furrow of the digestive tube wall starts to develop on the dorsal-posterior region of the yolk sac and divides the alimentary canal into two differentiated regions: the future stomach and intermediate intestine. At this time spiral valve starts to differentiate. Granules of embryonic pigment accumulate in the spiral valve lumen forming the melanin plug. 7 days after hatching intermediate gut and spiral gut are lined by a columnar ciliated epithelium. The terminal section of the digestive tract is differentiated into a short rectal duct lined with a cuboidal epithelium. The urinary bladder connects with rectum at this time. 13 days after hatching the number of vacuoles filled with lipid increases in intermediate gut and spiral gut. Between 17-19 days post hatching beluga larvae have a period of mixed nutrition. 25 days after hatching cells of intermediate gut have long microvilli. 36 days after hatching the number of goblet cells increase in spiral gut. 43 days after hatching several intestine glands are visible in connective tissue of intermediate gut which is lined by a simple columnar ciliated epithelium. Between 57-75 days after hatching the number and size of mucosal folds increase in intestine. This information may be useful to improve rearing efficiency of beluga and the other sturgeon.