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 entero-cyte 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.