Complete mitochondrial genome of an abyssal cusk-eel <i>Barathrites iris</i> (Ophidiiformes: Ophidiidae)

<i>Barathrites iris</i> Zugmayer, 1911 is an abyssal fish species inhabiting depths exceeding 3,000 m. We successfully sequenced and characterized the complete mitochondrial genome of <i>B. iris</i>, which represents a closed circular molecule of 16,646 bp with a GC content of 48.98%. Phylogenetic analysis of Ophidiiformes based on whole mitochondrial genome sequences demonstrated that <i>B. iris</i> forms a sister group with <i>Penopus microphthalmus</i> while supporting the polyphyly of Bythitidae as well as the paraphyletic status of Ophidioidei. As the first report of a complete mitochondrial genome for <i>B. iris</i>, this study provides valuable genomic resources for investigating deep-sea adaptation mechanisms in Ophidiiformes and contributes to our understanding of evolutionary patterns in abyssal teleost fishes.