Histological development of the digestive tract of flower spiny eel (Mastacembelus favus) was observed during early life stages (from 1 to 35 days after hatching) using light microscopy. At hatching, the digestive tract cavity is filled with yolk, mouth and anus are not yet opened. Three days after hatching (AH), mouth opened with mouth size (in height) of 0.37±0.07 mm and 4 regions of digestive tract could be easily distinguished as the buccal capvity, the oesophagus, a future stomach, and the intestine. Yolk sac resorbtion was completely at day 7 AH. However, larvae started exogenous feeding at day 6 AH, at this time the stomach was not developed completely, suggesting a period of mixed nutrition. The first histological evidence showing fat accumulation appeared at day 6 AH as lipid vacuoles in the intestine. The stomach formed from day 12 AH with a simple columnar epithelium and only circular muscle layer was identified. The glandular stomach with numerous simple and tubular gastric glands appearance in day 21 indicated that the development of digestive system was completed. To determine suitable time of using artificial diet for larval rearing, live food was totally replaced by commercial diet (45% crude protein) at day 15, 20, 25 and 30 AH. Fish in control treatment and before applied artificial diet in other treatments were fed with cladocerans and tubifex worm. Results showed that the highest survival (98%) and growth rate (17.71 mg/day) were observed in control treatment. In other treatments replaced with artificial diet, growth and survival rate of fish have significantly lower than those found in control. High mortalities were recorded in day 6 and 7 after shifted to artificial diet in treatments replaced live food by day 15 and 20 AH. It is probably due to starvation when the digestive tract is not fully developed. Survival rates significantly increased if larvae were fed artificial feed after stomach complete functionality.

 Keywords: Mastacembelus favus, digestive development, functional stomach, artificial diet.