Abstract
N-3 long-chain polyunsaturated fatty acids (LC-PUFA), particularly docosahexaenoic acid (22:6n-3, DHA), are the most important fatty acids with physiological significance in brain function of all vertebrates. Recently, novel lipid sources are available for the industry, including products obtained from microorganisms. Dietary fatty acid profiles may affect tissue composition and cell functioning. To determine the effect of novel lipid sources on behaviour and neural function in gilthead sea bream (Sparus aurata), juveniles were fed three isoproteic and isoenergetic diets containing either (FO), a microalgae oil combined with poultry oil (DD) or only poultry oil (PO). Behaviour response, brain fatty acid composition and relative expression of neurogenesis and neural activity related-genes in telencephalon were evaluated during 5 months of feeding with the experimental diets. Brain of sea bream fed diet PO showed the highest DHA content as well as increased desaturation and elongation products, contrary to the dietary pattern. This, together with an increased telencephalic fads2 expression denoted the effective activation of LC-PUFA synthesis and retention as a compensatory mechanism for a dietary deficiency. Furthermore, neurod6, bdnf and nos1 were proportionally upregulated in relation to the neural DHA content. Locomotor performance during cruising and escape responses was not affected by the experimental diets. However, there was a tendency for escape latency to be longest in fish fed PO and DD diets, and a relationship between escape latency and brain n-6 docosapentaenoic acid (DPA) contents was suggested. Indeed, the relation of n-6 DPA with behavioural deficits was shown previously in mammals and might deserve further attention and corroboration in fish as well in the future.
Highlights
N-3 long-chain polyunsaturated fatty acids (LC-PUFA) are involved in several metabolic pathways, such as energy production, membrane structure and function, control of lipid homeostasis and production of eicosanoids (Tocher, 2003)
No significant differences were observed in ce phalic index after 2.5 months of feeding, whereas after 5 months of feeding, cephalic index was higher in fish fed DD and poultry oil (PO) diets compared to those fed the fish oil (FO) (P < 0.05; Fig. 1B)
There was a tendency for escape latency to be the longest in fish fed PO and DD diets (P = 0.1; Fig. 2E), which is in line with the significant correlation found between escape latency and individual brain n-6 docosapentaenoic acid (DPA) contents, with a low r2 value (r2 = 0.18; P = 0.03; Fig. 3)
Summary
N-3 long-chain polyunsaturated fatty acids (LC-PUFA) are involved in several metabolic pathways, such as energy production, membrane structure and function, control of lipid homeostasis and production of eicosanoids (Tocher, 2003). The high demand for n-3 LC-PUFA from the brain in early stages of life is one of the most significant reasons behind the considerable higher DHA and EPA requirements in larvae than in juveniles or sub-adult fish (Izquierdo, 2005) Despite these important functions in fish neuromodulation, there is still little information regarding the effects of dietary n-3 LC-PUFA on brain function of teleosts. Some work has been carried out on larvae of farmed fish species, very few studies have been conducted to understand the impact of n-3 LC-PUFA in brain and behaviour responses of fish in later stages of development and, to our knowledge, no studies were carried out in gilthead sea bream (S. aurata) juveniles This topic deserves further attention on more species for a number of reasons: (1) With the increasing replacement of fish oil (FO) in aquafeeds, mostly with terrestrial plant ingredients, n-3 LC-PUFA dietary contents could be significantly reduced. Aquaculture 550 (2022) 737873 studying the effect of novel oils as lipid sources for aquafeeds and alternative to FO, on fish neural function could contribute to increasing our knowledge in these fields
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
