THE LIPID-COMPOSITION OF SELECTED TISSUES FROM A MEDITERRANEAN MONK-SEAL, MONACHUS-MONACHUS

The lipid composition of blubber, brain, muscle and heart from a Medit erranean monk seal Monachus monachus (an endangered species) were exam ined to allow comparisons with more common species of seals. Only neut ral lipids (mainly triacylglycerols) were detectable in the blubber li pids, whereas polar lipids predominated in the heart and in the brain. Neutral and polar lipids comprised almost equal proportions in both l iver and muscle. Choline glycerophospholipids (CGP) were the major pol ar lipids, followed by ethanolamine glycerophospholipids (EGP) in the liver, heart and muscle. Cerebrosides accounted for 28.8% of the brain lipids. All lipid classes of the liver contained high levels (31-47%) of polyunsaturated fatty acids (PUFA), with the exception of phosphat idylserine. The total proportion of n-6 PUFA exceeded that of n-3 PUFA in all lipid classes of the liver, due mainly to the high levels of 2 0:4n-6. The highest level of 20:4n-6 occurred in phosphatidylinositol, where it comprised 32.4% of the total fatty acids. The CGP and EGP of the brain contained lower levels of PUFA than those of the liver, mus cle and heart. Alkenyl ethers accounted for 35.8% of the total long-ch ain moieties in brain EGP. The fatty acid composition of blubber triac ylglycerols differed from those of the lipid classes from other tissue s in that it had a very low ratio of n-6 to n-3 PUFA (0.3) as a result of a lower content of 20:4n-6.