WILLIAMS, Judith L.; Univ. of Southern Miss Gulf Coast: What determines lipid content in copepods preparing for long-term dormancy?

The storage of lipids prior to dormancy is a widespread phenomenon in animals that diapause or hibernate. Lipid class and fatty acid content are highly variable, even within members of the same genus. Copepods undergo long term dormancy as a copepodite, sexually immature adult or a diapause egg. All stages store liquid lipid prior to diapause. Why do copepods store their fuel for dormancy as a liquid wax ester or triacylglycerol, and what determines the type of lipid stored? Work on diet and lipids in polar calanoid copepods suggests lipid type is determined by available food prior to dormancy. Does it not matter whether the copepod stores and utilizes wax esters as opposed to triacylglycerols? Are both equally sufficient to promote cell and tissue growth and reproduction following termination of dormancy? Specific enzymes (desaturases) desaturate fatty acids to their final form. Perhaps the inherent difference in a species ability to produce lipids is based strictly on their genetic makeup. For example, the enzyme polyketide synthase, which synthesize PUFA, is active at low temperatures. Is it downregulated in hot temperatures or is it lacking in warm water organisms? Research on biochemical pathways for other than polar copepods is sparse and our understanding of critical survival physiology in copepods is limited. Our laboratory is investigating lipids from one species of copepod known to produce diapause eggs, Eurytemora affinis, from two geographically distinct areas, one hot, and one cold. We are analyzing lipid classes of wild populations and comparing that to copepods reared in the lab and fed the same food for a short amount of time, then a longer period of time, to see if there is a shift in synthesis of lipid class and fatty acid content.