Figure 6.

The δ¹³C of essential fatty acids (EFA) in the animal is comparable to that of the symbionts or the external prey, since little or no isotopic fractionation occurs during this process. However, for the de novo synthesis of fatty acids from pool of acetate in the animal tissue: Transferases/desaturases induce an isotope depletion in the synthesized fatty acid, while elongase adds carbon atom from the acetate pool and thereby provides the isotope enrichment in the synthesized fatty acid (modified from Gladyshev et al., 2012)