The complete mitochondrial genome of a marine polychaete, Prionospio cf. japonica (Annelida: Spionidae)

Prionospio Malmgren 1867 is one of the abundant genera of the family Spionidae Grube, 1850. Despite its rich diversity, information on their complete mitochondrial genome has remained unknown. In this study, we determined the complete mitochondrial genome of a spionid polychaete, Prionospio cf. japonica Okuda 1935. The specimen was collected from the fine sand in the intertidal zone of South Korea. The mitogenome consists of 15,267 base pairs, harboring 13 protein-coding genes (PCGs), 22 transfer RNAs, and two ribosomal RNAs. The maximum-likelihood phylogenetic tree based on the 11 PCGs showed that Prionospio cf. japonica grouped with other spionid polychaetes and formed a monophyletic group. Also, the mtDNA of P. cf. japonica was more closely related to that of non-polydorin spionid, Marenzelleria neglecta, than polydorin spionids. The molecular data will be valuable for studying evolutionary relationships among annelids.