Abstract
Seasonal changes in biochemical indicators of physiological status were analyzed in abdominal muscle of the Antarctic krill, Euphausia superba, collectedfrom Port Foster, Deception Island , an active volcano locatedin the ShetlandIslandchain west of the Antarctic Peninsula. Krill were collectedwith a 10 m 2 MOCNESS trawl during four cruises (November 1999, February, May, November 2000). RNA:DNA mirroredthe chlorophyll a concentration, with the highest values found during seasons of abundant phytoplankton. Activities of the glycolytic enzyme lactate dehydrogenase (LDH) and the mitochondrial enzyme citrate synthase (CS) were significantly higher in male krill when comparedto females of similar size, indicating that their burst andaerobic swimming performance may be higher than females throughout the year. RNA:DNA ratio andenzyme activities were highly elevatedin summer as comparedto the earliest spring sampling period. Krill showed significant seasonal changes in LDH activity, with lowest values in spring andhighest values in summer (females) or autumn (males). Krill showedsignificant seasonal changes in CS activity with highest values in summer. Protein and% water variedsignificantly among seasons for both males and females. Lower CS activity and RNA:DNA ratio suggest krill exhibit reduced metabolism during the winter when phytoplankton production is reduced, perhaps enhancing survival. Lower enzyme activities in female krill in early spring suggest they may achieve greater metabolic suppression during overwintering. r 2003 Elsevier Ltd. All rights reserved.
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