First events in lipid absorption during post-embryonic development of the anterior intestine in gilt-head sea bream

Structural development and lipid absorption in anterior intestine of gilt-head sea bream Sparus aurata, were studied by light and electron microscopy during three stages of post-embryonic development: (1) the endotrophic period from hatching day (day 0) to mouth opening day (day 3); (2) the endo-exotrophic period from days 3 to 15; (3) the exotrophic period after day 15. During the 2 days following hatching, there was no trace of lipids in intestinal epithelia. Before mouth opening day, the first lipoproteic particles of endogenous origin appeared in enterocyte endoplasmic reticulum and Golgi apparatus. During the endo-exotrophic period, lipoproteinogenesis increased weakly until day 9, and more greatly between days 9 and 15. It intensified at the beginning of the exotrophic period to remain at a high level afterwards. Until day 15, few transfers of lipoproteins to interenterocyte spaces occurred, whereas no lipoproteins were detectable in the blood flow from days 7 to 9. Their concentration increased slightly between days 9 and 15 to become intense afterwards. Lipid droplets appeared from day 7, and subsisted until the end of endo-exotrophic period. Possible relationships between very low density lipoproteins and chylomicron type lipoproteins and lipid droplets related to lipid excess in food are discussed. (C) 1997 The Fisheries Society of the British Isles.