Northern Krill Meganyctiphanes Norvegica Research Articles

The physiological response of Northern krill (Meganyctiphanes norvegica) to temperature gradients in the Kattegat

The Alkor-Deep (140 m), which forms part of a depression system in the northern Kattegat channel east of the island of Laeso (Denmark), is the location of a self sustaining population of Northern krill, Meganyctiphanes norvegica (Euphausiacea). This population is exposed to one of the most pronounced thermal gradients within the distributional range of this pelagic crustacean. During summer, the temperature of the water column ranges between 4 and 6 in the deep to 16 °C near the surface which results in the krill being exposed to temperature differences of 8–10 °C during diel vertical migration. Oxygen consumption rates were used to investigate the physiological adaptation of the animal to such gradients in temperature. The rates were found to increase exponentially from 31 μmol O2 h-1 gdw-1 at 4 °C to 72 μmol O2 h-1 gdw-1 at 16 °C, giving a Q10-value of 2.0, and indicating that physiological adaptation to varying thermal conditions does not take place. Behavioural adaptations are discussed which may help the krill to cope with large temperature gradients in their environment.

Vertical migration behaviour in the northern krill Meganyctiphanes norvegica is influenced by moult and reproductive processes

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 190:253-262 (1999) - doi:10.3354/meps190253 Vertical migration behaviour in the northern krill Meganyctiphanes norvegica is influenced by moult and reproductive processes G. A. Tarling1,*, J. Cuzin-Roudy2, F. Buchholz3 1Scottish Association for Marine Science, PO Box 3, Oban, Argyll PA34 4AD, Scotland, UK 2Observatoire Océanologique, UPMC CNRS INSU LOBEPM, Océanographie biochimique et Ecologie, BP 28, 06230, Villefranche-sur-Mer, France 3Biologische Anstalt Helgoland, Stiftung AWI, Meeresstation, Postfach 180, 27483 Helgoland, Germany *E-mail: gant@dml.ac.uk ABSTRACT: A population of the northern krill Meganyctiphanes norvegica was sampled between 24 July and 3 August 1998 in the Alkor Deep, Kattegat, in order to investigate the influence of sexual and developmental factors on the vertical distribution of adult krill. Depth-discrete samples of krill were taken with a 1 m2 MOCNESS net at the cardinal times of day (midnight, midday, sunrise and sunset). Specimens were immediately measured and categorised for moulting and spawning status. Further samples were preserved for detailed analysis in the home laboratory. Results showed that the population concentrated in the deep (80 to 100 m) during day-time but segregated vertically during night-time. Moulting occurred in the deep during night-time, away from the main part of the non-moulting population, which was located between 80 and 50 m. Spawning females were most evident in the uppermost depth interval (30 to 5 m). Moulting at night in the deepest layers may be viewed as a mechanism to avoid cannibalism whilst in a vulnerable condition. Spawning in the warm upper layers accelerates reproductive processes and may also reduce the depth to which the eggs sink before hatching into nauplii. KEY WORDS: Northern krill · Euphausiids · Swarming · Diel vertical migration · Spawning · Moulting · Sexual behaviour Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 190. Publication date: December 14, 1999 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1999 Inter-Research.

Seasonal variations in the lipid and fatty acid composition of the euphausiid Meganyctiphanes norvegica from the Ligurian Sea

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 186:199-210 (1999) - doi:10.3354/meps186199 Seasonal variations in the lipid and fatty acid composition of the euphausiid Meganyctiphanes norvegica from the Ligurian Sea Patrick Mayzaud*, Patti Virtue, Eric Albessard Observatoire Océanologique, Océanographie Biochimique et Ecologie, ESA-CNRS 7076, BP 28, 06230 Villefranche-sur-Mer, France *E-mail: mayzaud@ccrv.obs-vlfr.fr ABSTRACT: Lipid and fatty acid composition of the northern krill Meganyctiphanes norvegica from the Mediterranean Sea were studied with respect to sex and season. Detailed composition of the lipid classes is reported for both males and females during the spring reproductive season and the late summer non-reproductive season. Both sexes showed similar lipid structure, with neutral lipids dominated by triacylglycerols. Polar lipids were dominated by phosphatidylcholine. Fatty acid compositions of both polar lipids and triacylglycerols showed little change with sex or season. Polar lipids were dominated by HUFA (20:5n-3 or EPA and 22:6n-3 or DHA) as well as palmitic and oleic acid. Neutral lipid fatty acid profiles were dominated by 22:6(n-3) and palmitic acid, with a significant contribution of oleic, myristic, stearic and vaccenic acids as well as 20:5(n-3). Seasonal changes in total lipids showed maximum accumulation in early summer and minimum levels in early winter. Changes in fatty acid composition appeared related to the succession of populations with varying levels of triacylglycerols, as illustrated by the contrast between the early winter and spring periods in a correspondence analysis. Increased proportions of myristic, palmitoleic and 18:4(n-3) acids during the spring period are characteristic of the triglyceride fraction while the main descriptor of the winter period is DHA, which is the key constituent of the polar lipids. Comparison with literature data illustrated the clear decrease in lipid content of northern krill with latitude and the specific nature of the seasonal pattern recorded in the Ligurian Sea. The regional variability in fatty acid composition and the significance of fatty acids as potential markers of feeding behaviour are discussed in relation to the omnivorous character of M. norvegica. KEY WORDS: Northern krill · Lipids · Ligurian Sea Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 186. Publication date: September 17, 1999 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1999 Inter-Research.

Studies on the seasonal biochemistry of the Northern krillMeganyctiphanes norvegica in the Kattegat

A well defined pelagic population of the Northern krill,Meganyctiphanes norvegica was sampled annually at a specific location in the Skandinavian Kattegat, and the major biochemical components were measured. Protein and lipid were the main constituents and underwent the most pronounced seasonal changes, clearly correlated to the prevailing supply of food organisms. The amount of lipid increased to a maximum of 48% of the dry weight towards winter, out of phase with gonad maturation, and therefore interpretable as deposition of overwintering reserves. Utilisation of stored reserves proceeds over winter, with loss of lipid, and decrease in weight but not in length. Comparison with literature data showed similarities with other krill populations from different geographical locations. The biochemical components ofEuphausia superba, the key organism of the marine Antarctic ecosystem, resembled those ofM. norvegica. Special polar adaptations are not obviously expressed in the proximate biochemical composition.