Influence of tropho-climatic environment and reproduction on lipid composition of the euphausiid Meganyctiphanes norvegica in the Ligurian Sea, the Clyde Sea and the Kattegat

Abstract

Lipid content and lipid-class distribution in the northern krill Meganyctiphanes norvegica (M. Sars, 1857) was investigated in 3 contrasting (in terms of climatic and trophic conditions) areas: the Ligurian Sea, the Clyde Sea and the Kattegat. Seasonal differences in the lipid content of krill were closely related to food supply coupled with the krill reproductive state in both the Ligurian Sea and in the Clyde Sea. In the Kattegat, the lipid reserves of reproductive krill were low and probably used continuously over a longer reproduction period and successive spawning cycles. In the Ligurian and Clyde Seas, female krill lost 55 and 33% of their cephalothorax (CT) lipids through spawning. The content of triacylglycerol (TAG) and phosphatidylcholine (PC), both major lipids in the CT, were higher when food conditions were optimal at the 3 sites, and were correlated to chlorophyll a (chl a) concentration in the Ligurian and Clyde Seas. The influence of reproduction on lipid-class distribution in the Clyde and Ligurian Seas was expressed by a large decrease in PC and TAG throughout spawning, while in the Kattegat PC and TAG levels were low irrespective of the reproductive state. The relative influence of environmental and physiological factors on the lipid distribution of krill in the CT and abdomen (AB) among the 3 locations was evaluated using principal components analysis. In the CT, TAG and PC along with minor lipids were major discriminating factors and were strongly correlated to total lipid content and chl a concentrations. For reproducive krill, marked differences in the CT and AB indicated covariation between reproduction and trophic conditions. The influence of the physical environment on M. norvegica at sexual rest found expression in variation in the membrane lipids in the AB across the different temperature and salinity regimes at the 3 sites. The results are discussed in terms of adaptive mechanisms involving lipid distribution and metabolism developed by the species.

Physiology and Metabolism of Northern Krill (Meganyctiphanes norvegica Sars)

“…Krill from the Greenland Sea contained 6% WE which accounts for 1.6% DM (Kreibich et al, 2010). No WE were found in krill from the Norwegian Balsfjorden , or the Ligurian Sea, the Scottish Clyde Sea, and the Danish Kattegat (Albessard and Mayzaud, 2003;Mayzaud et al, 1999). Thus, M. norvegica seems not to follow a typical high-latitude lipid storage strategy where WE are preferentially accumulated.…”

“…The thorax of krill from the Trondheimfjord contained 15.8% lipids on a dry weight basis and the abdomen just 9.1% (Saether et al, 1986). Albessard and Mayzaud (2003) reported that the lipid content in the cephalothorax from Ligurian, Kattegat, and Clyde Sea krill was 2-4 times greater than in the abdomen.…”

“…It contains 8% lipids on a dry weight basis. The lipid composition reflects the predominance of phospholipids from biomembranes and shows low levels of neutral lipids like TAG (Albessard and Mayzaud, 2003). The relative amount of the body lipids in resting males from the Ligurian Sea is summarised in Table 4.2.…”

“…The lipid content in the separate organs of M. norvegica varied significantly with season and the reproductive cycle; details are given by Albessard et al (2001) and Albessard and Mayzaud (2003).…”

“…PL in krill from the Greenland Sea made up 29% of total lipids (Kreibich et al, 2010). This accounts for about 8% on a dry weight basis or 2-3% on a wet weight basis (Albessard and Mayzaud, 2003). The relative amount of PC remains constant at different total lipid amounts because, besides the formation of biomembranes, PC is involved in egg production (Albessard et al, 2001;Cuzin-Roudy et al, 1999).…”