WILLIAMS. J.*; BIESIOT, P.M.: Fatty Acid Profiles Associated with Diapause Egg Production in Two Species of Freshwater Calanoid Copepods

The copepods Aglaodiaptomus (= Diaptomus) stagnalis and A. clavipoides co-occur in certain ephemeral ponds. Both species hatch from diapause (resting) eggs when pond sediments are freshly inundated and mature rapidly to adults. Both are believed to be univoltine, producing resting eggs only. In order to understand how diapause eggs are sustained during a potentially long dormancy, lipid classes and fatty acid profiles of the two species were compared. Our previous study showed that female A. stagnalis with egg sacs had higher concentrations of specific fatty acids compared to females without eggs. The specific objective of the present study was to determine if essential fatty acids, required for growth and development of all animals, are preferentially mobilized from females to their eggs. Males, non-gravid females and gravid females were assayed; egg sacs containing developing diapause eggs were removed from gravid females so th! at eggs and mothers were analyzed separately. Our results confirm that high concentrations of specific fatty acids are incorporated into the diapause eggs of A. stagnalis but not of A. clavipoides. In the former species, concentrations of both linolenic (18:3w3) and linoleic acid (18:2w6) are higher in eggs than in females which in turn have higher concentrations than males. However, all life history stages of A. clavipoides have similar concentrations of these two fatty acids. Although concentrations of omega-3 fatty acids are generally higher in eggs of A. stagnalis than in adults, concentrations of the essential fatty acids eicosapentaenoic acid (20:5w3) and docosahexaenoic acid (22:6w3) are lower. In contrast, concentrations of these fatty acids are similar in eggs and adults of A. clavipoides.