ORGANOGENESIS OF THE LIVER IN SEA BREAM

Development of the liver in sea bream, Sparus aurata, was studied usin g light and electron microscopy from hatching to the age of 23 days. H istochemical reactions were used to monitor changes in lipids and glyc ogen during this period. During the strictly endotrophic prelarval pha se from hatching until mouth-opening, the primordial liver formed by b udding on the gut wall and became organized in contact with the vitell ine vesicle. The initially undifferentiated cells rapidly polarized an d became pyramidal in outline with their apical extremities terminatin g in cavities corresponding to the future bile canaliculi. Sinusoids f ormed centripetally. Glycogen was stored in the cytoplasm of different iating hepatocytes. At the beginning of the larval stage the hepatocyt es multiplied, bile canaliculi were completed and the sinusoids acquir ed their final form. Glycogen reserves decreased strongly as bile secr etion started. The end of the endo-extrophic period was marked by dist inct recovery of glycogen storage, synthesis of numerous lipoproteins and discharge into the sinusoids. (C) 1995 The Fisheries Society of th e British Isles