Fig. 5: Independent diversification of Hox genes in Anthozoa and Medusozoa.

a, A conserved Hox cluster is not present in the Cnidaria, and genomic regions where Hox genes are located are considerably different in the Anthozoa and Medusozoa. Syntenic genes are connected with lines, and genes with a homeobox domain are shown as red boxes. Syntenic genes without a homeobox domain are shown as white boxes. Black boxes represent genes without orthologues within genomic segments. b, Mini-clusters of Medusozoa-specific Hox genes are present in Aurelia (scaffold 7) and Morbakka (scaffold 70). Members of these clusters are expressed strictly in polyp (green boxes) or jellyfish stages (red boxes). c, Expression dynamics of Hox genes in polyp and jellyfish stages of Aurelia and Morbakka. Groups of genes with polyp- or jellyfish-specific expression are present. d, Putative ParaHox cluster in Aurelia, and the corresponding genomic arrangement in Morbakka, where the ParaHox cluster is absent. e, Expression of Hox and ParaHox genes in tissues of Aurelia jellyfish. Bell-proxy, slice of the bell without edge part; ecto-up, ectoderm of exumbrella. f, Three ParaHox genes are present in the Medusozoa and are linked in Aurelia, while Cdx has not been identified in the anthozoans.