Body shrinkage as a possible over-wintering mechanism of the Antarctic krill, Euphausia superba Dana

Abstract

Antarctic krill ( Euphausia superba Dana) were maintained successfully for 211 days without food. A significant reduction in body size (32.1–56.1% of initial wet wt) was observed. Compared with wild animals starved E. superba decreased their oxygen uptake, ammonia excretion and phosphate excretion considerably (24–52%), but no significant changes in wet: dry wt ratio, and chemical compositions (C, N, P) were observed. The mortality of the starved group was similar to that of controls fed Tetra Marin and frozen copepods and less than that of controls fed a mixture of microalgae ( Dunaliella and Phaeodactylum). Because of insufficient lipid storage, E. superba is hypothesized to switch from herbivorous feeding to omnivorous or carnivorous during the Antarctic winter. The present results suggest, however, that body shrinkage could be an alternative way for this animal to conserve energy during the winter. The advantage of this is discussed in the light of the characteristics of body structure and life style of E. superba.