PP19 - Diet affects the redox system in developing Atlantic cod (Gadus morhua) larvae

Abstract

The growth and development of marine fish larvae fed natural copepods is superior to those fed rotifers, but the underlying molecular mechanisms are unclear. In this study we compared the effects of such diets on redox regulation pathways during development of Atlantic cod (Gadus morhua) larvae. Cod larvae were fed a control diet of copepods comprising species that are typical feed for cod in nature, or the standard rotifer/Artemia diet commonly used in commercial marine fish hatcheries, from first feeding until after metamorphosis. The oxidized and reduced glutathione levels, the reduction potential, and the mRNA expression of 100 genes in the redox system pathways were compared between the two treatments and at different defined stages during larval development. Growth was similar in the two groups the first 22 days after hatching, thereafter the growth was 2-fold higher in the copepod-fed fish until both groups were weaned onto a formulated diet. We found that rotifer/Artemia-fed cod larvae had generally lower levels of oxidized glutathione, a more reduced redox potential, and altered expression of nearly half of the redox system genes when compared to copepod-fed larvae. The rotifer/Artemia diet-induced an apparent dysregulation of the redox system that was greatest during periods of suboptimal growth. Upregulation of the oxidative stress response transcription factor, nfr2, and NFR2 target genes in rotifer/Artemia fed larvae suggest this diet induced an NFR2-mediated oxidative stress response. Overall, the data demonstrates that nutrition plays a major role in the redox regulation of developing fish larvae. This may well be a key factor for the dietary-induced differences observed in larval growth. The nutrient composition of diets and larvae were analysed and we will present an evaluation of how the different nutrients may have contributed to differences in growth and redox biology.