VARIATION OF DIGESTIVE ENZYMES AND MOUTH WIDTH DURING LARVAL DEVELOPMENT OF CHINESE LONGSNOUT CATFISH (LEIOCASSIS LONGIROSTRIS G躈THER) FED WITH ARTEMIA

Ontogentic changes of four digestive enzymes (amylase, lipase, trypsin, pepsin) and the morphological parameters of total length and mouth width were investigated in Chinese longsnout catfish larvae fed with Artemia. The experiment lasted for 13 days. The results showed that 1) total length (TL) and mouth width (MW) of the larvae increased linearly with time after hatching (RTL2=0.974, RMW2=0.964; PP<0.05) and then reached to a plateau at 0.07—0.08. The fact that mouth width developed synchronically with total length from 7dph indicated the beginning of the weaning time. All the digestive enzymes were detected at the first feeding. Trypsin activity was significant higher in 5—7dph larvae than that of the newly hatched fish, which accompanied the first feeding behavior at 5dph. Pepsin and lipase activities in 7dph larvae and amylase activities in 6dph larvae were significantly higher than that of the newly hatched larvae. The high and stable activities of the digestive enzymes during 8—13dph indicated that the digestive tract was fully developed.