Three different lipid sources in formulated start-feeds for turbot (Scophthalmus maximus, L.) larvae - effect on growth and mitochondrial alteration in enterocytes

Abstract

Turbot, Scophthalmus maximus, larvae were start-fed with formulated feeds containing soya phospholipids (SP), marine phospholipids (MP) or triacylglycerol (TAG). The levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were the same in the MP and TAG feeds. The control group was given rotifers (R). The larvae were offered feed from day 4 post-hatch. Larvae fed formulated feed with added MP showed good initial growth and there were no significant differences in weight on day 6 between this group and the group given rotifers. Using feed with added TAG enriched with EPA and DHA gave no growth at all. Using SP as the lipid source in the feed resulted in reduced initial growth. Electron microscopical examination of enterocytes was performed on larval intestines on day 6. Larvae fed MP, TAG or rotifers had normal looking enterocytes with numerous normal looking mitochondria. In the enterocytes of larvae fed SP the mitochondria appeared swollen with a translucent matrix and fragmented cristae. Thus, SP or TAG appear not to be suitable as the sole source of lipids and/or phospholipids in start-feed for turbot larvae and the effects of MP are not solely caused by high levels of EPA and DHA.