Lipid Transformations of Euchaeta antarctica, a Carnivorous Marine Copepod

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This research will address the ecology of an Antarctic predatory copepod, Euchaeta antarctica, a biomass dominant and important macroplanktonic carnivore in Croker Passage, a deep basin off the Antarctic peninsula. Previous work has shown that size-selective feeding on crustacean prey more than adequately covers respiratory costs so excess dietary input could be stored by this large lipid-rich copepod. With the onset of winter, feeding stops, respiration and excretion rates decline and oxygen/nitrogen ratio increases, indicating a shift from a protein and lipid based metabolism to a lipid-dominated metabolism, corroborating summer feeding activity and winter reliance on lipids. During winter, nearly all females are reproductively mature, producing multiple clutches of lipid-rich eggs from their maternal stores. Early stages mature slowly so the first feeding stage appears in the plankton in synchrony with the active bloom in southern waters. The extreme seasonality of food availability in this polar region enforces the separation of 2 processes: feeding in summer and reproduction in winter. This project will complete the lipid analyses, an essential component of this research. Samples, previously collected, permit an analysis of total lipid content, lipid class composition and production rates by different copepodid stages during three different seasons, and by different reproductive states of the adult female in the winter. This work will allow for an evaluation of whether the stored reserves are sufficient to provide energy to support winter metabolic rates and reproductive demands and will provide an understanding of the linkage between lipid content/composition and life history strategies.