Qualitative needs of lipids by mullet, Mugil cephalus, fry during freshwater acclimation

The mass evolution of phospholipids and triacylglycerols of mullet fry was studied using a decreasing salinity (0.5‰) at constant temperature. After 4 weeks of acclimation (0.5‰), high concentrations of phospholipids (9.75 mg/g wet weight) and triacylglycerols (49.77 μmoles/g w/w) were observed in fry acclimated in seawater (35‰) compared to fry in freshwater (0.5‰) which had levels of 6.56 mg/g w/w and 7.32 μmol/g w/w, respectively. Significantly, high levels of phosphatidylcholine (PC) were observed in fry acclimated to freshwater (960.48 μg/g w/w) compared to those in seawater (591.97 μg/g w/w). Radioactivity distribution, after injection of labelled acetate at 14C, was significantly higher in fry acclimated to seawater in the triacylglycerol. However, high levels of radioactivity were incorporated in PC in fry acclimated to freshwater. High levels of PC in fry acclimated to freshwater could serve as precursor synthesis of triacylglycerols. The enrichment of food for mullet fry with lecithin (PC) is necessary during acclimation before their introduction into freshwater (0.5‰) to reduce mortality.