APPEARANCE OF LIPID-ABSORPTION CAPACITIES IN LARVAE OF THE SEA BASS DICENTRARCHUS-LABRAX DURING TRANSITION TO THE EXOTROPHIC PHASE

The development of intestinal lipid absorption capacities was studied in larvae of the sea bass Dicentrarchus labrax from the time of mouth opening to 25 d after hatching, in individuals fed with brine shrimp, Artemia sp. (Brazil commercial strain) or artificial diets. At the time of mouth opening, before the first feed, enterocytes synthesized lipoprotein particles from endogenous lipids. Starting with the first feed, enterocytes absorbed food lipids regardless of the diet, but since these cells have a low capacity for lipoprotein synthesis, they accumulated lipids in the form of "free" lipid droplets. In larvae fed with Artemia sp., the rapid development of enterocytes during growth was combined with increasingly effective lipoprotein synthesis (becoming even greater than that observed in the adult), starting on Days 18 to 19. Although lipoprotein synthesis and transport were observed in larvae given artificial feed, they showed abnormalities in their intestinal mucosa. Lipid droplets formed in association with the membrane structures of specimens given egg yolk during the first days of feeding, and enterocytes degenerated. In 18 to 19 d-old larvae given artificial feed, intestinal folds disappeared and the constituent cells showed limited differentiation. In the last-mentioned individuals, the abnormalities appeared to be related to malnutrition resulting from inadequacy of the food offered, which led to total mortality of larvae, beginning on Day 20.