Figure 1. Biosynthetic pathway of LC-PUFA as determined in mammals and teleosts (all reactions shown), and octopus (confined to reactions in the two ellipses).

(A). Elongation (Elovl), desaturation (Δ4, Δ5 and Δ6) and β-oxidation (β-oxi) reactions are indicated. The omega-3 (ω3) and omega-6 (ω6) PUFA synthesis cascades are shown in parallel. Each composite number (e.g. 18:3) refers to a specific PUFA, with the first number indicating the number of carbon atoms and the second referring to the ethylenic bonds (details on each PUFA in supplementary Table 1). Phylogenetic tree of the major Bilaterian animal groups considered in this study (B). Genome duplications are indicated (2R and 3R).