ALBERT

Description: Three dominant Antarctic copepods, Calanoides acutus, Rhincalanus gigas and Metridia gerlachei (copepodite stages V and females), were collected during summer (January/ February) in the southern Weddell Sea south of 70°S Detailed analyses of their lipid and fatty acid/ alcohol compositions were carried out. The trophic positions of these copepods were elucidated by means of the lipid compositions (marker lipids). High amounts of wax esters were found in C. acutus (92% of total lipids) and in R. gigas (84-86%). The level of wax esters in M. gerlachei was relatively low (27-42%), while the accumulation of triacylglycerols tended to be higher (19-22%). Characteristic lipid components of C. acutus were the long-chain monounsaturated fatty acids and fatty alcohols 20:1 (n-9) and 22:1 (n-il). These components together with elevated amounts of the 18:4 (n-3) and, to a lesser degree, of the 16:1 (n-7) fatty acids, typical of phytoplankton lipids, indicatc herbivorous feeding for C. acutus. Other abundant fatty acids were 20:5 (n-3) and 22:6 (n-3). Thc fatty acid composition of M. gerlachei was characterized by very high amounts of these 22:6 and 20:5 acids. Other important fatty acids werc 18:1 (n-9) and 16:0, but only small amounts of 16:1 (n-7) and 18:4 (n-3) occurred. In contrast to C. acutus the fatty alcohols of M. gerlachei consisted almost exclusively of the short-chain components 14:0 and 16:0. M. gerlachei is known as an omnivorous species, which was clearly reflcctcd by its lipid and fatty acid/alcohol pattern. Few data arc available on the feeding of R. gigas, but it is usually describcd as an herbivorous small-particle feeder. R. gigas showed fatty acid/alcohol characteristics typical of either C. acutus or M. gerlachei. Higher amounts of the 16:1 (n-7) and 18:4 (n-3) fatty acids suggest herbivorous feeding, whereas the dominance of short-chain alcohols (14:0 and 16:0) resembled the lipid pattern found in the omnivorous M. gerlachei. Hence, the lipid composition of R. gigas showed an intermediate pattern, which implies a tendency towards an opportunistic feeding mode, positioned somewhere between the other two species.

Description: The composition of the intact wax esters of Calanus hyperboreus, C. finmarchicus, and C. glacial is from the Fram Strait area of the Greenland Sea was studied. In addition the fatty acid and alcohol composition of the wax esters was analysed. All copepods were rich in wax esters, especially C. hyperboreus in which long-chain wax esters were generally more abundant than in the other species.The wax ester composition was species dependent but strongly overlapped by spatial variabilities. Because phytoplankton fatty acids were partially incorporated directly into wax esters, the composition of the wax esters was widely influenced by the phytoplankton community which itself varied considerably in the Fram Strait region. Thus, the wax esters of the polar species, collected in the North East Water Polynya near Greenland, were dominated by diunsaturated compounds in the range from C32 to C44. The shorter chain components resulted from a combination of palmitoleic acid which is typical of diatom lipids with long-chain alcohols. In the marginal ice zone, higher levels of polyunsaturated wax esters were detected due to the presence of the 18:4 fatty acid, typical of a summer phytoplankton population.

Description: The dominant large copepods Calanoides acutus and Calanus propinquus were collected south of 65°S in the Antarctic Weddell Sea in late winter/early spring (October-November) and summer (January-February), and the lipid and fatty acid/alcohol compositions of copepodite stages V and females of these suspension feeders were analyzed. The lipids of C. acufus consisted mainly of wax esters. Major fatty acids in summer were 20:1(n9), 20:5(n3), 22:6(n3), 18:4(n3), 22:1(n11) and 16:1(n7). In winter the amount of 18:4(n3) decreased considerably in both stages, as did that of20:5(n3) in females, whereas the quantity of 20:i(n9) showed a strong increase in females. During both seasons the fatty alcohols in the wax esters were strongly dominated by 20:1 (n9) and 22:1 (n11). In contrast, the hulk of the lipids of C. propinquus were triacylglycerols with the principal fatty acids 22:1(n11), 22:1(n9), 16:0, 20:5(n3) and 22:6(n3). Hence, an alternative to the paradigm of energy storage by means of wax esters, typical of C. acufus and almost all other calanoid copepods from polar and temperate oceans, was found for C. propinquus. The synthesis of these energy-rich triacylglycerols occurs via an unusual marine biochemical pathway, the elongation of the 20:1(n9) to the 22:1(n9) fatty acid. Our data show the existence of very different biochemical solutions to the problem of efficient energy storage for coping with the extreme seasonality in Antarctic waters, with short periods of food plenty interchanging with long phases of food scarcity.

Description: Lipid compositions of the dominant Antarctic copepods Calanoides acutus, Rhincalanus gigas and Calanus propinquus from the Weddell Sea have been investigated in great detail. Copepods were collected during summer in 1985 and late spring/early winter in 1986. The analyses revealed specific adaptations in the lipid biochemistry of these species which result in very different lipid components. The various copepodite stages of C. acutus synthesize wax esters with long-chain monounsaturated moieties and especially the alcohols consisted mainly of 20:1(n-9) and 22:1(n-1 1). R. gigas also generates wax es-ters, but with moieties of shorter chain length. The fatty alcohols consisted mainly of 14:0 and 16:0 components, while the major fatty acids were 20:5, 18:4 and 22:6, of which 18:4 probably originated from dietary input. In contrast, C. propinquus accumulates triacylglycerols, a very unusual depot lipid in polar calanoid copepods. Major fatty acids in C. propinquus were the long-chain monounsaturates 22: l(n-9) and 22: 1(n-l 1), which may comprise up to 50% of total fatty acids. In C. acutus and C. propinquas there was a clear increase of long-chain fatty acids with increasing developmental stage. In contrast, the fatty acid and alcohol composition of the R. gigas copepodite stages were characterized by the dominance of the polyunsatu-rated fatty acids as well as high amounts of the monoun-saturates 18:1(n-9) and 16:1(n-7). There was a considerable decrease of the dietary fatty acid 18:4(n-3) towards the older stages during summer; in late winter/early spring 18:4 was only detected in very low amounts. This tendency was also found in the other two species, but was less pro-nounced. In all three species dry weight and lipid content increased exponentially from younger to older stages. Thehighest portion of wax esters, or of triacylglycerols in C. propinquus, was found in the adults. Dry weight and lipid content were generally higher during summer. In late winter/early spring the variability was more pronounced and lipid-rich specimens showed a selective retention of long-chain monounsaturated fatty acids, whereas in lipid-poor specimens these fatty acids were very much depleted.