Seasonal variations in the lipid and fatty acid composition of the euphausiid Meganyctiphanes norvegica from the Ligurian Sea

Lipid and fatty acid composition of the northern kriil Meganyctiphanes norvegica from the Mediterranean Sea were studied with respect to Sex and season.Detailed composition of the lipid classes is reported for both males and females during the spring reproductive season and the late surnmer non-reproductive season.Both Sexes showed simiiar lipid structure, with neutral lipids dominated by tnacylglycerols.Polar iipids were dominated by phosphatidylcholine.Fatty acid compositions of both polar lipids and triacylglycerols showed little change with Sex or season.Polar lipids were dorninated by HUFA (20511-3 or EPA and 22:6n-3 or DHA) as well as palmitic and oleic acid.Neutral Lipid fatty acid profiles were dominated by 22:6(n-3) and palmitic acid, with a significant contribution of oleic, myristic, steanc and vaccenic acids as well as 20:5(n-3).Seasonal changes in total iipids showed maximum accumulation in early summer and minimum levels in early winter.Changes in fatty acid composition appeared related to the succession of populations with varying levels of tnacylglycerols, as iilustrated by the contrast between the early winter and spring penods in a correspondence analysis.Increased proportions of mynstic.palmitoleic and 18:4(n-3) acids dunng the spring penod are characteristic of the triglycende fraction while the main descnptor of the winter period is DHA, which is the key constituent of the polar lipids.Cornpanson with literature data iilustrated the clear decrease in lipid content of northern krill with latitude and the specific nature of the seasonal pattern recorded in the Ligurian Sea.The regional vanability in fatty acid composition and the sigmficance of fatty acids as potential markers of feeding behaviour are discussed in relation to the omnivorous character of A4. norvegica.