ONTOGENIC AND SEASONAL-CHANGES IN LIPID AND FATTY-ACID ALCOHOL COMPOSITIONS OF THE DOMINANT ANTARCTIC COPEPODS CALANUS-PROPINQUUS, CALANOIDES-ACUTUS AND RHINCALANUS-GIGAS

Lipid compositions of the dominant Antarctic copepods Calanoides acutu s, Rhincalanus gigas and Calanus propinquus from the Weddell Sea have been investigated in great detail. Copepods were collected during summ er 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 sta ges of C. acutus synthesize wax esters with long-chain monounsaturated moieties and especially the alcohols consisted mainly of 20:1(n-9) an d 22:1(n-11). R. gigas also generates wax esters, 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 th e long-chain monounsaturates 22:1(n-9) and 22:1(n-11), which may compr ise up to 50% of total fatty acids. In C. acutus and C. propinquus the re was a clear increase of long-chain fatty acids with increasing deve lopmental stage. In contrast, the fatty acid and alcohol composition o f the R. gigas copepodite stages were characterized by the dominance o f the polyunsaturated fatty acids as well as high amounts of the monou nsaturates 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 su mmer; in late winter/early spring 18:4 was only detected in very low a mounts. This tendency was also found in the other two species, but was less pronounced. In all three species dry weight and lipid content in creased exponentially from younger to older stages. The highest portio n 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 pronounc ed and lipid-rich specimens showed a selective retention of long-chain monounsaturated fatty acids, whereas in lipid-poor specimens these fa tty acids were very much depleted.