Seadragon genome analysis provides insights into its phenotype and sex determination locus.

The iconic phenotype of seadragons includes leaf-like appendages, a toothless tubular mouth, and male pregnancy involving incubation of fertilized eggs on an open "brood patch." We de novo-sequenced male and female genomes of the common seadragon () and its closely related species, the alligator pipefish (). Transcription profiles from an evolutionary novelty, the leaf-like appendages, show that a set of genes typically involved in fin development have been co-opted as well as an enrichment of transcripts for potential tissue repair and immune defense genes. The zebrafish mutants for , which is lost in all syngnathids, were found to lack or have deformed pharyngeal teeth, supporting the hypothesis that the loss of has contributed to the loss of teeth in syngnathids. A putative sex-determining locus encoding a male-specific gene shared by common seadragon and alligator pipefish was identified.