a, Fatty acid synthesis and transport-related domains are expanded in the MHS compared with the other species tested (CO, cod; FF, flatfish; FU, Fugu; PB, Pacific bluefin tuna; PF, platyfish; SF, stickleback; TS, Tanaka’s snailfish; ZF, zebrafish). ‘Row z score' refers to the z score calculated for each value in the grid square within the row it belongs. This shows the significance of expansion. A complete list of expanded domains in the MHS is provided in Supplementary Table 13. b, Expanded genes (coloured blue) in the DHA biosynthesis pathway. In the chmical structure of DHA, the ω represents the methyl end, and the numbers indicate the positions of the carbon atoms. 22:6 indicates there are 22 carbons and 6 double bonds. c, Rapidly evolving Gene Ontology categories. These points represent mean Ka/Ks ratios for pairs of MHS and Tanaka’s snailfish genes by Gene Ontology category. Each point is coloured based on the significance (P value, one-sided binomial test) of the accumulation in non-synonymous mutations. A complete list of categories is provided in Supplementary Table 14.