Development of the Gastrointestinal Tract in Sharpsnout Sea Bream (Diplodus puntazzo) Larvae: Histological and Enzymatic Ontogeny

Digestive system ontogeny of the sharpsnout sea bream (Diplodus puntazzo L., 1758) was detected from hatching until 40 Days After Hatching (DAH) using histological techniques and enzymatic assays. At hatching, total length of larvae measured at 2.8 +/- 0.34 mm and it was determined on 40 DAH as 11.84 +/- 1.76 mm. At mouth opening (3 DAH), larvae almost absorbed their yolk-sac reserves. An incipient stomach could be distinguished at 2 DAH. The first evidence of gastric glands development was detected at 28 DAH, increasing in number and size by 33-40 DAH. In the fundic region, gastric gland determined as strogly and mucusal acinar cell accumulates at 30 DAH and the intestinal mucous cells appeared and developed between at 10-28 DAH. Then, functional stomach formation was detected for the first time on 32 DAH supported with sudden increase on activity of acid protease. In terms of digestive protease activity, alkaline protease was detected as early as hatching and also suddenly increased after starting of exogenous feeding. Developmental pattern for alkaline protease demonstrated constant enhancement, until metamorphosis at 25 DAH. After this date, this activity slowly decreased until end of the experiment. In contrast to this, acidic protease activity exhibited relatively lower activities during the early stages. Afterwards, concurrently with the formation of functional stomach at 32 DAH, acid protease activity suddenly >3-fold enhanced and continued to increase until end of the experiment. It is concluded that organogenesis of alimentary tract and ontogeny of digestive proteases in D. puntazzo larvae followed the same general pattern that most Sparidae species.