1 Provided for non-commercial research and educational use only. Not for reproduction, distribution or commercial use. This chapter was originally published in the book Advances in Marine Biology – Biology of Northern Krill - 57, published by Elsevier, and the attached copy is provided by Elsevier for the author's benefit and for the benefit of the author's institution, for non-commercial research and educational use including without limitation use in instruction at your institution, sending it to specific colleagues who know you, and providing a copy to your institution’s administrator. All other uses, reproduction and distribution, including without limitation commercial reprints, selling or licensing copies or access, or posting on open internet sites, your personal or institution’s website or repository, are prohibited. For exceptions, permission may be sought for such use through Elsevier's permissions site at: http://www.elsevier.com/locate/permissionusematerial From: Geraint A. Tarling, Natalie S. Ensor, Torsten Fregin, William P. Goodall- Copestake, and Peter Fretwell, An Introduction to the Biology of Northern Krill (Meganyctiphanes norvegica Sars). In GERAINT A. TARLING editor: Advances in Marine Biology – Biology of Northern Krill - 57, Burlington: Academic Press, 2010, pp. 1-40. ISBN: 978-0-12-381308-4 © Copyright 2010 Elsevier Inc. Academic Press.