MEPS 170:203-213 (1998) - doi:10.3354/meps170203
Lipid metabolism of the Antarctic euphausiid Euphausia crystallorophias and its ecological implications
Gerhard Kattner1,*, Wilhelm Hagen2
ABSTRACT: Euphausia crystallorophias is the dominant krill species in high-Antarctic waters and thus has to cope with the most extreme environmental conditions of all euphausiids. To study its lipid biochemical adaptations, various developmental stages were collected during different seasons in the southeastern Weddell Sea. Lipids declined from very high levels in the eggs (51.4% of dry mass) to low levels in the calyptopis larvae and moderate amounts in the furciliae. Postlarval stages accumulated maximum lipid contents (51.5%) in autumn, whereas minimum levels of 6.5% occurred in late winter/early spring. Wax esters were the primary storage lipid in E. crystallorophias, reaching highest amounts in autumn with a mean of 55.6% of total lipid. They were also the major lipid class in the eggs. The most abundant fatty acid in the immature and adult specimens was 18:1(n-9). In the wax esters this fatty acid accounted for up to 75% and together with the 18:1(n-7) fatty acid comprised up to 90% of total wax ester fatty acids. The fatty acid composition of the eggs was very similar to that of the females. The predominance of the 18:1 fatty acids is an extraordinary lipid characteristic within the marine zooplankton community. It was less pronounced in the younger stages, where 16:0, 20:5(n-3) and 22:6(n-3) were also important fatty acids. Together with the 18:1(n-9) fatty acid, the above were generally the principal components of the phospholipids. The alcohol moieties of the wax esters consisted almost exclusively of the 2 saturated shorter-chain fatty alcohols 14:0 and 16:0. Fatty acids and alcohols increased linearly with total lipid mass and total lipid content, independent of developmental stage, sex, region, season and food supply. The predominant 18:1(n-9) fatty acid exhibited the highest accumulation rate, triple that of the second most abundant fatty acid 20:5(n-3). The seasonal and ontogenetic lipid compositions suggest that these energy reserves play an important role in metabolic maintenance during the overwintering period and, in particular, allow reproductive processes to take place in late winter/early spring, independent of primary production.
KEY WORDS: Krill · Euphausiids · Lipid storage · Wax esters · Fatty acids and alcohols · Overwintering · Reproduction
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