Changes in lipid composition during metamorphosis of bonefish (Albula sp.) leptocephali

During metamorphosis of bonefish (Albula sp.) larvae (leptocephali) all energy requirements are provided by breakdown of endogenous compounds, with lipid catabolism accounting for about 80% of total energy production. The principal objective of the present study was to characterize the lipid classes and fatty acids utilized. Analysis of whole-body lipid content indicated that larvae lost about half (3.6 mg) of their total lipid during the 10-d period. Percentages of neutral and polar lipid in early metamorphosing larvae were 64.2 and 35.8%, respectively; these values showed little change during metamorphosis, indicating that both lipid classes were catabolized. Triacylglycerols, the principal neutral lipid of all metamorphic stages, decreased by 1.8 mg, accounting for half of the decrease in total lipid. Levels of phosphatidylethanolamine, the principal polar lipid in early larvae, decreased by more than 50% during metamorphosis; levels of phosphatidylcholine, which was not detected in early larvae, increased. Fatty acids showing the largest net decreases, presumedly used as energy sources, were 16:0 (30.4%), 14:0 (13.8%), 16:1n-7 (12.2%), 20:5n-3 (7.7%), 18:1n-9 (7.4%), and 18:4n-3 (6.9%). Most of 22:6n-3, the second most abundant fatty acid of early larvae, was conserved.