Development of digestive enzymes in common dentex Dentex dentex during early ontogeny

The digestive physiology of common dentex was studied by assessing the activity of different pancreatic (trypsin, chymotrypsin, amylase and lipase), intestinal (alkaline phosphatase maltase and leuncine-alanine peptidase) and gastric (pepsin) enzymes from hatching until the juvenile stage (50 dph at 19 degrees C). Enzymes involved in the digestion of protein, lipid and carbohydrate were present in common dentex larvae at hatching and before the onset of exogenous feeding. The specific activity of trypsin and chymotrypsin in newly hatched larvae was higher than that of amylase and lipase,indicating the importance of these enzymes in the cleavage of yolk proteins and hatching, while after hatching. the activity of these serine proteases dramatically decreased, whereas lipase showed the opposite trend. A progressive shift in activity front alkaline to acid proteases was observed during larval development, reflecting that alkaline proteases were not longer the main digestive enzymes involved in protein digestion after the development of gastric glands and onset of acidic digestion. Lipase total activity in common dentex peaked at 35 dph and decreased after weaning. Diet change due to weaning might partially explain file decrease in lipase activity, although this change might be also indicative of a change in the nutritional requirements of this species, since the juveniles prefer diets with high protein levels than those with lower protein and higher lipid content. Regarding intestinal enzymes, leucine-alanine peptidase and alkaline phosphatase and aminopeptidase N were found in newly hatched larvae, while maltase was detected after the onset of exogenous feeding. The achievement of an efficient brush border membrane digestion takes place much earlier (6-12 dph) than in any of the Studied species which might reflect the different metabolic profile and rapid growth of this species. (C) 2008 Elsevier B.V. All rights reserved.