The role of lipids in winter survival of Antarctic zooplankton

Abstract

Two species of adult Antarctic krill, Euphausia superba and E. crystallorophias, and two species of adult Antarctic copepods, Pareuchaeta antarctica and Calanoides acutus, were collected and analyzed for total lipid and lipid classes to understand the role of lipids in overwintering survival of Antarctic zooplankton. We estimated the lipid utilization rates of Antarctic zooplankton during winter based on the differences of total lipid content in organisms collected from Marguerite Bay in fall and winter. This estimate indicates that C. acutus utilize the least amount of lipid (237 μg lipid/g DW/day), mainly as triacylglycerols, among investigated zooplankton because low energy requirement for C. acutus during winter diapause. In contrast, P. antarctica utilized the most amount of lipid (1600 μg lipid/g DW/day), mainly as wax esters, due to their continual active behavior during winter. Estimated lipid utilization rates for E. superba and E. crystallorophias were 633 and 1174 μg lipid/g DW/day, respectively. Of particular interest was that both krill species utilized typical storage lipids (triacylglycerol for E. superba and wax ester for E. crystallorophias) as well as membrane lipids (phospholipids), demonstrating that structural phospholipids can also serve as energy stores in Antarctic krill. Combining other studies of metabolic rates with the contribution of lipids for E. superba suggests that lipids contribute only 20% of energy requirement needed to maintain the metabolic activity of E. superba during winter. Therefore, E. superba is less dependent on lipid reserves than other zooplankton,and must depend on additional strategies (i.e., body shrinkage, etc.) to survive during winter.