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Marine Biology

, Volume 149, Issue 6, pp 1443–1452 | Cite as

On the timing of moulting processes in reproductively active Northern krill Meganyctiphanes norvegica

  • Cornelia M. BuchholzEmail author
  • Friedrich Buchholz
  • Geraint A. Tarling
Research Article

Abstract

The interactions between moult phasing, growth and environmental cues in Northern krill (Meganyctiphanes norvegica) were examined through analysing populations at seasonal, weekly, and daily timescales. The analyses were carried out on resident populations of krill found in three different neritic locations that experience similar environmental signals (the Clyde Sea, Scotland; the Kattegat, Denmark; Gullmarsfjord, Sweden). Seasonal analyses were carried out on the Clyde Sea population and showed that moulting frequency increased significantly moving from winter to summer. The proportion of moulting females in summer samples was often more than double the proportion of moulting males, suggesting that females had a comparatively shorter intermoult period (IMP). Weekly samples taken from the Kattegat showed a similar pattern. However, although the difference between the proportion of female and male moulters was significant in one week, it was not another, mainly because of the variability in the proportion of female moulters. Such variability in females was equally evident in the daily samples taken at Gullmarsfjord. It suggests that females have a shorter IMP (12.5 days) than males (18.4 days) and are more likely to moult in synchrony. Nevertheless, the daily samples revealed that males are also capable of moult synchronisation, although less frequently than females. Shortened IMPs in females were not a result of the abbreviation of specific moult stages. Accordingly, reproductive activity did not alter the course of the normal moult cycle. There was no significant difference between the total body lengths of males and females indicating that females achieve the same levels of growth despite moulting more frequently and having to provision the energy-rich ovaries. This is in contrast to most other crustaceans where the energy costs of reproduction reduce female growth. The fact that females were less abundant than males, probably by suffering a greater level of mortality, suggests that different behavioural strategies, particularly vertical migration regimes, were adopted by each sex to maximise growth and reproduction.

Keywords

Somatic Growth Antarctic Krill Moult Cycle Moult Stage Spring Phytoplankton Bloom 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgements

The hospitality and efficient support at Kristineberg Marine Research Station and the kind help of Jalle Strömberg are gratefully acknowledged. The scientific and ship’s crew of FS “Heincke” contributed substantially to the sampling in the Kattegat, as well as those on RV “Calanus” in the Clyde Sea and on RV “Oskar von Sydow” in the Gullmarsfjord. Janine Cuzin is thanked for her eager interest in our work and hours of discussion. The work was supported by grants from the Transnational Access funds to KMRS and EU-MAST III (MAS3-CT95-0013), “The PEP Programme.” Fieldwork in the Clyde, carried out by GT, was funded by a NERC postdoctoral fellowship (GST/59818MS). GT’s contribution to the data analysis was carried out as part of the FLEXICON project of the DISCOVERY 2010 programme at BAS. We wish to express our gratitude to three anonymous advisors who spent their time and consideration to help us improve the manuscript.

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Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  • Cornelia M. Buchholz
    • 1
    Email author
  • Friedrich Buchholz
    • 1
  • Geraint A. Tarling
    • 2
  1. 1.Biologische Anstalt Helgoland – AWIHelgolandGermany
  2. 2.British Antarctic SurveyNatural Environment Research CouncilCambridgeUK

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