25The high mortalities observed during Octopus vulgaris paralarvae culture have been 18:2n-6, 18:3n-3, 20:4n-6 (ARA), 20:5n-3 (EPA) or 22:6n-3 (DHA), which were added 33 directly to the seawater as their potassium salts bound to bovine serum albumin (BSA). 34A control treatment without [ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 3 50 Introduction 51The common octopus (Octopus vulgaris) is a cephalopod species that has been 52 suggested as a candidate for large scale culture (Vaz-Pires et al., 2004), not only due to 53 its high nutritional value and demand in several countries, but also due to biological 54 characteristics such as short life cycle, rapid growth, high fecundity rate, easy 55 adaptability to rearing conditions, high food conversion rates and acceptance of non-56 living natural foods during the juvenile and adult stages (Estefanell et al., 2011; Iglesias 57 et al., 2007; Vaz-Pires et al., 2004). 58Currently this species is being cultured in NW Spain by ongrowing wild-captured sub-59 adults in land-based tanks or sea cages until they reach 2-3 Kg (Iglesias et al., 2007). Iglesias et al., 2007; Moxica et al., 2002; Viciano et al., 2011; Villanueva and Norman, 73 2008). A recent study was able to determine a predominance of crustacean zoeae in wild 74O. vulgaris paralarvae diet (Roura et al., 2012 Miliou et al., 2006; Navarro and Villanueva 2003; Okumura et al., 2005). 81Among those, polyunsaturated fatty acids (PUFA), and particularly 20:5n-3 (EPA) and 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 8 220 ± 1.5 %) and phosphatidylcholine (PC, 19.6 ± 0.6 %) as the main PL classes (Table 1). 221Cholesterol was the most abundant lipid class of octopus hatchlings, corresponding to 222 30.1 ± 2.9 %, and TAG and sterol esters (SE) accounted for 1.2 ± 0.4 and 2.1 ± 0.8 % of 223 TL, respectively (Table 1). 224The O. vulgaris hatchlings were particularly rich in the n-3 LC-PUFA, DHA and EPA, might be related to the energy-generating FA oxidation systems (Sargent et al., 1989). 321In marine fish larvae, NL and more specifically TAG are presumably used to satisfy 64 65 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 11 322 energy demands (Rainuzzo et al., 1997, Sargent et al., 1989, with SFA and MUFA 323 being the main substrates. In contrast, LC-PUFA are preferentially esterified into PL, 324revealing their important structural role in cell membranes (Sargent et al., 1989). FA was suggested (García-Garrid...

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The long-chain (≥C 20 ) polyunsaturated fatty acid biosynthesis capacity of fish varies among species, with trophic level hypothesised as a major factor. The biosynthesis capacity is largely dependent upon the presence of functionally diversified fatty acyl desaturase 2 (Fads2) enzymes, since many teleosts have lost the gene encoding a Δ5 desaturase (Fads1). The present study aimed to characterise Fads2 from four teleosts occupying different trophic levels, namely Sarpa salpa , Chelon labrosus , Pegusa lascaris and Atherina presbyter , which were selected based on available data on functions of Fads2 from closely related species. Therefore, we had insight into the variability of Fads2 within the same phylogenetic group. Our results showed that Fads2 from S . salpa and C . labrosus were both Δ6 desaturases with further Δ8 activity while P . lascaris and A . presbyter Fads2 showed Δ4 activity. Fads2 activities of herbivorous S . salpa are consistent with those reported for carnivorous Sparidae species. The results suggested that trophic level might not directly drive diversification of teleost Fads2 as initially hypothesised, and other factors such as the species’ phylogeny appeared to be more influential. In agreement, Fads2 activities from P . lascaris and A . presbyter were similar to their corresponding phylogenetic counterparts Solea senegalensis and Chirostoma estor .

The fatty acid profile of vegetable oils (VOs), together with the poor ability of marine fish to convert polyunsaturated fatty acids (PUFA) to highly unsaturated fatty acids (HUFA), lead to important changes in the nutritional value of farmed fish fed VO, which include increased fat and 18:2n-6 and reduced n-3 HUFA. Echium oil (EO) has a good n-3/n-6 balance as well as an interesting profile with its high content of unusual fatty acids (SDA, was also unaffected by EO in terms of total uptake, incorporation, β-oxidation and elongationdesaturation activities.

The aim of this study was to assess the effect of an experimental diet (ED), with high levels of 18:1 n-9 and low eicosapentaenoic to arachidonic acid ratio (EPA/AA), on the fatty acid (FA) profile of ovary and eggs of Seriola dumerili broodstock, in contrast to a non-specific commercial diet (nsCD), taking wild fish lipid composition as a positive reference. Two groups of Seriola broodstock born in captivity were fed with either the ED or the nsCD during two consecutive spawning seasons (21 months). After 7 months of feeding, fish fed the ED displayed an ovary FA profile much closer to wild fish. During the second spawning season, only the group fed ED released eggs. Egg FA composition showed some minor changes throughout the spawning season, with a marginal reduction of EPA in the late season being the most striking variation. Overall, the use of the ED showed some positive results, which could favor spontaneous egg release from females born in captivity. However, the lack of fertilization and the high level of 18:2 n-6 in the ovary tissue and eggs indicate that further improvements are needed in S. dumerili broodstock diet formulation in order to enhance the reproductive performance of this species in captivity.Practical applications: The use of the ED resulted in an ovary fatty acid profile of cultured females that better resembles that of wild fish. Using broodstock diets with balanced EPA/AA ratios (close to wild fish) may have a positive effect on fish broodstock reproductive performance, at least for this species.