Time course of changes in fatty acid composition in the osmoregulatory organs of the thicklip grey mullet (Chelon labrosus) during acclimation to low salinity

Changes in plasma osmolality haematology, lipid content and fatty acid composition of the gills, intestine and kidney of the Thicklip Grey Mullet (Chelon labrosus) were investigated along a salinity gradient from seawater (SW, 38 p.p.t.) to low salinity water (LSW, 5 p.p.t.). Plasma osmolality has changed as evidenced by the dynamics of the osmoregulatory parameters. These dynamics have revealed two stages during hyperosmotic and hypo-osmotic acclimations: (i) an adaptive period during the first days of acclimation (37days), with important changes in these parameters and (ii) a chronic regulatory period (after 3days of transfer) where osmotic parameters reached hom0eostasis. From a metabolic point of view, we found that salinity decrease induced mobilization of lipids in the gills, kidney and intestine of C. labrosus. We also observed changes in fatty acid profiles but with differences between tissues. In gills and intestine, SFAs and MUFAs decreased and PUFAs increased in the first day of the transfer. However, in the kidney, PUFAs increased and SFAs and MUFAs decreased at the end of the transfer. We conclude that the changes made during salinity acclimation are followed by a qualitative variation in the lipids and that the decrease in salinity leads to an improvement in the synthesis of PUFAs fatty acid. This suggests that lipids are important in meeting the energetic demands resulting from exposure to salinity.