A comparative analysis of the fatty acid composition of sexual and asexual eggs of Daphnia magna and its plasticity as a function of food quality

Abstract

In cyclical parthenogenetic Daphnia, asexual eggs develop immediately and enable fast population growth, while sexual eggs are dormant and can survive harmful conditions. We studied whether this different function is reflected in different fatty acid profiles and explored the capacity of D. magna to adjust fatty acid provisioning of its eggs depending on food resources. We quantified neutral- and phospholipid content of sexual and asexual eggs produced under different food conditions and compared these with eggs collected from a natural pond. In eggs obtained under different laboratory food regimes, total concentration of neutral fatty acids per unit biomass was not affected by food source or egg type. Both egg types contained lower amounts of fatty acids in the neutral fraction when produced in nature than under laboratory conditions. Fatty acid concentration in the phospholipid fraction was lower in sexual than asexual eggs. Fatty acid composition of eggs largely reflected that of the food of the mothers, albeit with small modifications. Sexual eggs produced on a diet of Scenedesmus obliquus (no C20-PUFA), contained higher concentrations of eicosapentaenoic acid and arachidonic acid in both fractions than asexual eggs.