Digestive Enzymes in Larvae and Juveniles of Farmed Sharpsnout Seabream (Diplodus puntazzo) (Cetti, 1777)

The ontogenetic development and pattern of main digestive enzyme activities (proteases, carbohydrases and lipases) were investigated in farmed sharpsnout seabream Diplodus puntazzo larvae and juveniles, during the passage from the larval stage to adult (from 21 to 277 days after hatching DAH). Larvae showed exponential growth, thus confirming that Rotifers and Artemia nauplii are suitable preys for early feeding of D. puntazzo larvae. Pepsin activity was low in the larvae, but it increased afterwards in relation with stomach development. In juveniles, levels of specific activity of trypsin, chymotrypsin and elastase were lower compared to that recorded in larvae. A decrease in the activity of the alkaline proteases could be related to an increase in the functionality of stomach. Qualitative and quantitative assay of glycosidases ( -amylase, cellulase and maltase) showed high glycosidase activity, indicating that D. puntazzo is capable of digesting carbohydrates in its diet. Levels of lipase activity in juveniles were higher than those found in larvae. Our results didn’t show an inductive character of lipases, since in juveniles the activity levels were almost constant even if the fat content of compound diet varied (from 7.0 % to 20 %). The rapid changes in the digestive activities of D. puntazzo larvae supported the existence of well established induction and regulation digestive mechanisms. Present results also confirm that D. puntazzo larvae have complete digestive enzymatic equipment that increased during larval ontogeny and enable larvae to digest and absorb nutrients contained in live preys once exogenous feeding occurred. The enzymatic pattern is correlated with omnivorous feeding habits of the species. Moreover, the patterns of activity of the main digestive enzymes of D. puntazzo larvae and juveniles indicated the early functional development of their digestive system and suggested this species as a good candidate for Mediterranean aquaculture using the compound diet.