SEASONAL LIPID STORAGE AS OVERWINTERING STRATEGY OF ANTARCTIC KRILL

Conflicting hypotheses prevail on the overwintering strategies of the Antarctic krill Euphausia superba due to the difficult accessibility o f Antarctic waters, especially in winter, and hence, to the lack of se asonal data. This study reports on the seasonal lipid dynamics of E. s uperba (25 to 56 mm) collected in the Weddell Sea in late winter/sprin g, summer, autumn and mid-winter. Total lipid data provide evidence of large seasonal accumulation of reserve lipids in austral summer with a mean Lipid content of 28.2% of dry mass and particularly in autumn, when mean lipid levels peak with 39.2% of dry mass. After the overwint ering period mean lipid contents decrease to a minimum of 10.5% of dry mass, indicating extensive utilisation of lipid reserves during winte r. These data suggest that lipids contribute significantly to the over wintering success of this extremely versatile species. Lipid class ana lyses of spring and summer specimens (10 to 56 mm) from the Antarctic Peninsula and the Weddell Sea revealed that not only triacylglycerol, but also phosphatidylcholine may serve as important storage lipids of E. superba. In the other dominant Antarctic krill species, E. crystall orophias (10 to 40 mm) and Thysanoessa macrura (10 to 27 mm), wax este rs are the primary depot lipid, but phosphatidylcholine also functions as a storage lipid in these species. Phosphatidylcholine is unusual a s a reserve lipid, being an essential component of biomembranes. In co ntrast, phosphatidylethanolamine, the other major phospholipid class, seems to have exclusively membrane functions, since it does not increa se (in percent of dry mass) with increasing lipid levels in these 3 eu phausiid species.