The complete mitochondrial genomes of two important octopus species from the eastern Pacific were sequenced, obtaining their complete nucleotide sequences. Octopus mimus is the most important commercially catched species along the eastern Pacific, from Mexico to Chile, whereas 'Octopus' fitchi is a pigmy species with uncertain taxonomic genus. The mitogenomes of Octopus mimus and 'Octopus' fitchi were 15,696 and 15,780 base pairs (bp) in length with an A + T composition of 75.5% and 75.8%, respectively. Each genome contains 13 protein-coding genes, 22 tRNA genes, and two rRNA genes, as well as a control region. Gene order is maintained as reported for other species of the Octopodidae. The phylogenetic analysis based on the concatenated thirteen protein-coding genes confirms that O. mimus belongs to the genus Octopus, which is supported by the genetic distance (11-16%) whereas the position of 'O'. fitchi within this group it is not supported. The analysis also indicated that the phylogenetic position of 'O'. fitchi is closer to Callistoctopus than to the Cistopus or the Amphioctopus clades. Based on the tree topology and the high genetic distance observed (24-25%), we suggest that 'O'. fitchi might represent a different genus.
Keywords: Mitogenome; Octopus mimus; Phylogeny; ‘Octopus’ fitchi.