The complete mitochondrial genome of <italic>Amphioctopus marginatus</italic> (Cephalopoda: Octopodidae) and the exploration for the optimal DNA barcoding in Octopodidae.

In this study, the complete mitochondrial genome of <italic>Amphioctopus marginatus</italic> (Cephalopoda: Octopodidae) was sequenced. The length of <italic>A. marginatus</italic> was 15,719 base pairs (bp) and the composition of genome is A (41.74%), T (33.53%), C (16.77%), and G (7.96%). The whole mitogenome was composed of 13 protein-coding genes (PCGs), 2 ribosomal RNA genes, 22 transfer RNA genes, and a major non-coding region. The overall A+T content of <italic>A. marginatus</italic> showed remarkable similarity to other Octopodidae species reported before, with the characteristic of extremely richer than G+C. The gene order of the protein-coding genes was identical to other octopodids, but the tRNA genes were rearranged, making the gene order unique. The phylogenetic analysis showed relationships between <italic>A. marginatus</italic> and <italic>Amphioctopus aegina</italic> is close. The new mtDNA data enriched the database, which was beneficial to refine the phylogenetic relationships within Octopodidae further. ND5 gene could become an optimal DNA barcoding in taxon identification of the family. [ABSTRACT FROM AUTHOR]