HISTOLOGY AND HISTOCHEMISTRY OF THE DEVELOPMENT OF THE DIGESTIVE-SYSTEM OF LARVAL GILTHEAD SEABREAM, SPARUS-AURATA L

Resorption of the yolksac and development of the digestive tract and a ssociated organs, including the swim bladder, were studied in Sparus a urata larvae from hatching until day 30 using histological and histoch emical procedures. At the onset of exogenous feeding three regions cou ld be easily distinguished in the gut: the foregut including the oesop hagus and a primordial stomach, the midgut and lastly the hindgut. At this time, the digestive tract was functional even though the stomach was not yet completely developed; gastric glands, for instance, were n ot present in the period studied. Glycogen and zymogen grains were sto red in the liver and pancreas, respectively between days 4 and 6 after hatching. Proteins were observed in the pancreas, hepatic vascular sy stem and to a lesser extent the hepatocytes. Once feeding had commence d, the anterior intestinal epithelium developed the capacity for the a bsorption of lipids, most of which were included in large lipid drople ts. Simultaneously, acidophilic supranuclear inclusions containing pro teins were observed in the posterior intestinal epithelium. All oesoph ageal mucous cells, intestinal goblet cells, epithelial columnar cells in the stomach, and enterocytes of the digestive epithelium were rich in carboxylated, sulphated and/or neutral mucosubstances. Proteins we re not present in digestive goblet cells.