Effects of dietary lipid profile on larval performance and lipid management in senegalese sole

The aim of this study was to evaluate the short- and long-term effects of diets consisting in rotifers enriched with different oil emulsions (differing mainly in triacylglycerols levels) and provided during the first week of life. Survival, growth, metamorphosis progress, lipid profile and molecular regulatory pathways were evaluated. For comparison purposes, a diet used routinely in the aquaculture industry based on microalgae was also carried out. The present study shows that dietary triacylglycerols (TAG) levels and fatty acid composition modulate larval survival and growth when supplied during larval pelagic stages. Histological observation and gene expression pattern showed that early larvae regulated intestinal lipid transport, showing a coordinate activation of apolipoproteins transcripts. Multivariate analyses identified the major contribution of apoEa to discriminate samples by dietary treatments, pointing out the importance of this apolipoprotein as key molecular marker for intestinal lipid mobilization. However, our data indicate that transport capacity is limited in early larvae, increasing in anterior intestine as intestine maturates with larval development, while the increase of fat deposits in the posterior intestine in older larvae supports the limited capacity of this gut section for lipid transport. The accumulation of TAG, phosphocholine (PC) and oleic acid (OA) along pre- and early metamorphosis indicates that these lipids influences positively daily mortality rate, eye-migration progress and growth. Moreover, larval TAG amounts correlate highly with apoA-IVBa3 mRNA levels, indicating an active role of this apolipoprotein in endogenous lipid mobilization during development. These data provide new evidence that TAG, PC and OA dietary levels are important for larval development and complement the available information about energy management in sole larvae reinforcing the rotifer feeding period as critical to produce high-quality larvae. Statement of relevance: This paper provides new clues about the mechanisms involved in lipid management in larvae and their consequences during their life-cycle to produce high-quality fry and optimize husbandry procedures