SS4.07 Lipids/Fatty Acids in Ecological Research
Date: Tuesday, June 11, 2002
Time: 5:00:00 PM
Location: Saanich
 
RavetJL, University of Washington, Seattle, USA, jlravet@u.washington.edu
Brett, M, T, University of Washington, Seattle, USA, mtbrett@u.washington.edu
Mueller-Navarra, D, C, University of California- Davis, Davis, USA, dcnavarra@ucdavis.edu
 
A direct test on the importance of essential fatty acids in determining algal food quality for herbivorous zooplankton
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A series of experiments were conducted using the herbivorous zooplankter Daphnia pulex to investigate the importance of dietary highly-unsaturated-fatty-acids (HUFA). Daphnia were raised on one of three diet types: a HUFA deficient cyanophyte spp. mixture, a cyanophyte mixture with fatty acid (FA) amendments, or a HUFA rich cryptophyte spp. mixture. We devised a novel method for delivering specific FAs in a pure and bioavailable form that mimics their form in natural diets using customized phosphatidylcholine liposomes. FA impregnated liposomes were added to the cyanophyte mixtures at levels equivalent to the observed differences in FA concentrations between the cyanophyte and cryptophyte mixtures. Liposome control amendments (without FAs added) had no effects on growth. EPA (20:5w3) amendments accounted for 30% of the growth differences between the cyanophyte and cryptophyte diets. A FA mixture that included the four FA prevalent in cryptophytes but rare in cyanophytes accounted for 50% of the growth differences between the cyanophyte and cryptophyte diets. In contrast to recently published results, our study suggests algal FAs play an important direct role in herbivorous zooplankton nutrition.