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

Abstract

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 (<i>Phyllopteryx taeniolatus</i>) and its closely related species, the alligator pipefish (<i>Syngnathoides biaculeatus</i>). 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 <i>scpp5</i>, which is lost in all syngnathids, were found to lack or have deformed pharyngeal teeth, supporting the hypothesis that the loss of <i>scpp5</i> has contributed to the loss of teeth in syngnathids. A putative sex-determining locus encoding a male-specific <i>amhr2y</i> gene shared by common seadragon and alligator pipefish was identified.