The complete mitochondrial genome and phylogenetic analysis of the polychaete Diopatra sp. (Annelida: Onuphidae)

The polychaete genus Diopatra is widely distributed in tropical and subtropical coasts and plays key ecological roles as an ecosystem engineer. Despite more than 65 recognized species, its taxonomy remains unresolved due to extensive cryptic speciation and limited molecular data. In this study, we sequenced and annotated the complete mitochondrial genome of Diopatra sp. collected from Incheon, South Korea. The mitogenome was 14,985 base pairs in length and contained 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, and two ribosomal RNA (rRNA) genes ( rrnS and rrnL ), consistent with typical metazoan organization. This mitogenome provides a genetic reference that supports comparative mitogenomic and phylogenetic analyses, as well as the resolution of cryptic diversity and accurate taxonomic assignment in environmental DNA (eDNA)-based biodiversity assessments. Phylogenetic analysis based on concatenated PCG sequences from 37 polychaete mitogenomes representing six families placed Diopatra sp. in a well-supported clade with Diopatra cuprea and Hyalinoecia robusta (Onuphidae) within the subclass Errantia. These findings reinforce the monophyly of Diopatra within Errantia and provide valuable genetic information for resolving the cryptic diversity, phylogenetic relationships, and evolutionary history of polychaetes.