Behavioral and Physiological Characteristics of the Antarctic Krill, Euphausia superba

• Published in: American Zoologist
• Main Authors: QUETIN, LANGDON B., ROSS, ROBIN M.
• Format: Text
• Language: English
• Published: Oxford University Press 1991
• Subjects: Articles; Antarctic; Antarctic Peninsula; Southern Ocean; The Antarctic; Weddell; Weddell Sea; Antarc*; Antarctic Krill; Euphausia superba
• Online Access: http://icb.oxfordjournals.org/cgi/content/short/31/1/49; https://doi.org/10.1093/icb/31.1.49

The antarctic krill, Euphausia superba , is considered a success in the intensely seasonal environment of the Southern Ocean because of its abundance and central role as an important food item for many of the larger carnivores in the ecosystem. The behavioral and physiological characteristics that foster this success are: (1) the ability to find concentrations of food in several types of habitat and efficiently exploit whatever food is available; (2) the close correspondence of the life cycle with seasonal cycles of food availability; and (3) a combination of physiological mechanisms that enable krill to survive the long winter period of low food availability. We evaluated the relative importance of the following four major winter-over mechanisms that have been proposed for adult krill west of the Antarctic Peninsula. The three-fold reduction in metabolic rate is the most important winter-over mechanism for these adults, although lipid utilization and shrinkage also help satisfy energy requirements in the winter. Alternate food sources did not appear to contribute significantly as a winter energy source. However, the extent, predictability and complexity of the ice cover in a region during winter may have a great influence on the relative importance of these winter-over mechanisms for different populations. Ice cover in the waters west of the Antarctic Peninsula is unpredictable and smooth surfaced when it occurs, providing the krill with little refuge from predation. In multi-year pack ice of the Weddell Sea, however, ice cover is predictable and extensive, and there is a complex undersurface that provides hiding places. In this multi-year ice, adult krill have been observed under the ice feeding, whereas west of the Antarctic Peninsula most adult krill are in the water column in the winter and are not feeding. The balance between acquiring energy and avoiding predation may be different in these two regions in the winter because of differences in predictability and complexity of the ice cover.