Lipid metabolism of the Antarctic euphausiid Thysanmssa macrura and its ecological implications

Abstract

The lipid biochemistry of one of the dominant Antarctic euphausiids, Thysanoessa macrura, was investigated in the Weddell Sea. Ontogenetic stages from furciliae to adults were collected during all seasons. Total lipid contents of these stages ranged from 5.5% to 60.5% of dry mass, with minimum levels in late winter/early spring (October/November) and maximum levels in autumn (April/May). Accordingly, wax esters, the primary storage lipid in T. macrura, also varied seasonally and reached a mean value of 66.6% of total lipid in autumn. Although lipid reserves are used partly for overwintering, the adults invest considerable amounts of these stores in reproductive processes such as gonad maturation, egg production, and mating in late winter prior to the vernal phytoplankton bloom. Total lipids were dominated by the fatty acids 16:0, 20:5(n‐3), and 22:6(n‐3), the principal components of the phospholipids. Other important fatty acids were 14:0 and 18:1(n‐9), which together with 16:0 prevailed in the wax esters. The alcohol moieties of the wax esters consisted of >90% of the isomers 18:1(n‐9) and 18:1(n‐7) and of 20:1 (n‐9). The dominance of 18:1 alcohols in T. macrura is unique among marine plankton. All fatty acids and alcohols exhibited linear relationships with increasing total lipid mass and with total lipid content, irrespective of the developmental stage, sex, region, or season. The fatty acids 16:0, 14:0, and 20:5(n‐3) and the two 18:1 fatty alcohol isomers had the highest accumulation rates, which explains their seasonal dominance in the lipid‐rich specimens. T. macrura has developed quantitative and qualitative energetic adaptations to cope with the pronounced seasonal variability in feeding conditions and reproductive requirements.