Arachidonic acid effects on the overall performance, fatty acid profile, hepatopancreas morphology and lipid-relevant genes in Litopenaeus vannamei juveniles

The effect of arachidonic acid (ARA) was evaluated on Litopenaeus vannamei juveniles. Growth performance; hepatopancreas and muscle fatty acid compositions; hepatopancreatic cells morphology; and expression of lipid-relevant genes were estimated after six-week experiment. A basal fat-reduced diet was manufactured and subsequently coated with different fatty acids sources, distinct levels of ARA (0, 0.3, and 0.6%), fish and soybean oil (50:50 Control diet). L. vannamei juveniles (1.10 +/- 0.22 g) were randomly divided into twelve tanks with thirty animals each. The animals were fed three times per day, with 8% of the total biomass. The results showed that animals fed with diet containing 0.3% of ARA presented a lower final weight compared to the Control. Different levels of ARA inclusion in the experimental diets directly influenced in the tissues fatty acid profile with lower ARA levels in Control and 0% followed by 0.3% and 0.6%. In muscle and hepatopancreas tissues, a higher accumulation of docosahexaenoic acid (DHA) was revealed in the Control compared to the rest of the experimental treatments. The expression pattern of lipoxygenase (alox5), prostaglandin E synthase (pges2), sterol regulatory element-binding protein-1 (srebp1) and cycloxygenase (cox2) were significantly affected by the ARA inclusion, showing the highest expression in the Control treatment with a decrease according to the increasing levels of dietary ARA. It is concluded that ARA inclusion in shrimp diets result in a negative impact on the overall performance, probably modulated by a differential gene expression related to the eicosanoids synthesis, lipolytic and lipogenic pathways. Besides, the lipid deposition on the hepatopancreatic cells was reduced.