The potential of dietary polyunsaturated fatty acids to modulate eicosanoid synthesis and reproduction in Daphnia magna: A gene expression approach

Nutritional ecology of the aquatic model genus Daphnia has received much attention in past years in particular with regard to dietary polyunsaturated fatty acids (PUFAs) which are crucial for growth and reproduction. Besides their significant role as membrane components, C20 PUFAs serve as precursors for eicosanoids, hormone-like mediators of reproduction, immunity and ion transport physiology. In the present study we investigate transcriptomic changes in Daphnia magna in response to different algal food organisms substantially differing in their PUFA composition using quantitative real-time PCR and relate them to concomitantly documented life history data. The selection of target genes includes representatives that have previously been shown to be responsive to the eicosanoid biosynthesis inhibitor ibuprofen. The beneficial effect of C20 PUFA-rich food on reproduction and population growth rates was accompanied by an increased vitellogenin (DmagVtg1) gene expression in D. magna. Additionally, genes involved in eicosanoid signaling were particularly influenced by dietary C20 PUFA availability. For example, the cyclooxygenase gene (Cox), coding for a central enzyme in the eicosanoid pathway, was highly responsive to the food treatments. Our results suggest that dietary PUFAs are fundamental in D. magna physiology as substrate for eicosanoid synthesis and that these eicosanoids are important for D. magna reproduction.