Abstract:The development of the digestive system of Centropristis striata and its associated glands were examined histologically from the first day (first day post-hatch, dph) until 34th day after hatching. Sampling was performed daily between 1 dph and 15 dph with sampling size around 30 fish. After that, sampling frequency was reduced to once every other day until 34 dph with sampling size of 15 fish. The newly-hatched larvae were reared in tanks with continuous supply of oxygen. Meanwhile salinity was about 30–32 and water temperature was maintained at (24±1)℃. It was found that the yolk sac of newly-hatched larvae was relatively large, while the digestive tract was a closed straight tube with a smooth lumen dorsally attached to the yolk sac. The mouth and anus formed and opened on the 3 dph, and followed by a 4-day period of mixed endogenous-exogenous feeding. Most of the yolk sac reserves were consumed rapidly; during this period, prey capture began and the digestive system continued to develop. Specifically, the digestive tract of larvae was differentiated into esophagus, stomach and intestine, and the digestive glands (1iver, gall-bladder and pancreas) began to form. Yolk sac and oil globule almost disappeared at 7 dph, and the nutritional requirements of the larvae has gradually made the transition from endogenous to exogenous. Mucous cells could be found in the epithelia of the oesophagus at 11dph, and the number of cells kept increasing during the larval development. Stomach was gradually differentiated into cardiacus, gastric body and pyloricus. At the same time, sinusoid and central veins of liver were clearly distinguishable. Gastric gland formed at 20 dph, which indicated the beginning of exogenous protein digestion. Increased wrinkles in the mucous layer and thicker muscles were detected in the intestine. Meanwhile, pancreas was abundant in zymogen granules spreading on the surrounding areas of the intestine. The structures and functions of digestive tract and digestive glands gradually became full-functional. It was concluded that C. striata larvae should be supplied with adequate and palatable food when they enter exogenous feeding period, and domesticated to feed formula feed after 20 dph. The findings on the development of the digestive system lead to a better understanding of the ontogeny of C. striata, which would be useful for improving the larval rearing techniques of this promising Centropristis species and therefore diversifying the freshwater aquaculture.
