Investigating the essential fatty acids in the common cuttlefish Sepia officinalis (Mollusca, Cephalopoda): Molecular cloning and functional characterisation of fatty acyl desaturase and elongase

Some polyunsaturated fatty acids (PUFA) play critical roles in physiology and are essential for normal growth and development of aquatic animals including cephalopods like the common cuttlefish Sepia officinalis. This is particularly true for early life stages when neuronal tissues are rapidly developing and accumulating PUFA. The specific fatty acids (FAs) that can satisfy the essential requirements of any animal species depend upon the enzymatic capability to convert dietary FA into those physiologically important FAs required for normal function. In order to identify the dietary essential FA for the common cuttlefish, we have performed the molecular cloning and functional characterisation of two key enzymes involved in PUFA biosynthesis in this species, namely a fatty acyl desaturase (Fad) and an elongation of very long-chain fatty acid (Elovl) protein. The gene product of the cuttlefish Fad exhibited ∆5-desaturase activity, enabling this species to potentially biosynthesise the physiologically essential FAs eicosapentaenoic (20:5n-3, EPA) and arachidonic (20:4n-3, ARA) acids from 20:4n-3 and 20:3n-6, respectively. However, the cuttlefish Fad did not show ∆6 or ∆8 activity and therefore the biosynthesis of EPA and ARA from C18 PUFA precursors could be limited, suggesting that both may be essential FAs for cuttlefish. Moreover, the cuttlefish Fad also lacked ∆4-desaturase activity suggesting that DHA biosynthesis was not possible and thus DHA is also an essential FA for this species. The cuttlefish ∆5 Fad was able to produce non-methylene-interrupted (NMI) FA, a group of PUFAs typically found in marine invertebrates. The cuttlefish Elovl was able to elongate C18 and C20 PUFA substrates, but showed no activity towards C22 PUFA. Overall the results obtained in the present study allowed the prediction of the biosynthetic pathways of PUFA, including NMI FA, in the common cuttlefish. It was concluded that EPA, ARA and DHA were likely to be essential dietary FA for this species as endogenous production from precursor FA appears to be limited

Assessment of stress and nutritional biomarkers in cultured Octopus vulgaris paralarvae: Effects of geographical origin and dietary regime

The common octopus (Octopus vulgaris) is a promising species for aquaculture diversification, but massive mortality during the first life-cycle stages (paralarvae) is the main bottleneck for its commercial production in captivity. The aim of this study was to assess stress and nutritional condition biomarkers (HSP70, ROS enzymes and lipid peroxidation) (RNA/DNA, RNA/protein, protein/DNA and protein) inO.vulgarisparalarvae from different geographical origins and fed withArtemiaenriched with marine phospholipids or microalgae (control group). To this end paralarvae were cultured for 30days, in three different centres in Spain (Tarragona-Mediterranean area, Tenerife-Central Atlantic area and Vigo-North Atlantic area), under the same protocol, and fed onArtemiaenriched with marine phospholipids (LC60) (Marine Lecithin LC 60®, PhosphoTech Laboratoires) or microalgae (control group). Dry weight and most biomarkers analysed in hatchlings showed significant differences related to their origin (centre). Fifteen day old paralarvae presented significant differences in specific growth rate (SGR) associated with their dietary regime, and also showed differences in biomarkers associated both with their geographical origin and dietary regime. The results suggest that the SGR of paralarvae were positively influenced by LC60, promoting growth and in agreement with the results of nutritional condition biomarkers (nucleic acids ratios). The antioxidant defences against oxidative damage were also boosted in the LC60 paralarvae group, possibly as a result of the elevated content in highly polyunsaturated fatty acids. In addition, the partial correlations found between biomarkers varied according to diet. However, no positive effect of LC60 on survival was observed. The high variability found among geographical origins, despite the use of the same rearing protocol, highlights the need to clarify the sources of such variability