Particular gene order and complete mitochondrial genome of Beach conger (Conger japonicus)

Beach conger (Conger japonicus) is a demersal and carnivorous species belonging to the family Congridae. In the present study, the complete mitochondrial genome of the C. japonicus was first determined. The mitochondrial genome of C. japonicus is 17,778 nucleotides, comprising 13 protein-coding genes, 2 ribosomal RNA genes, 22 tRNA genes, and 2 main non-coding regions (the control region and the origin of the light strand replication), which is consistent with other vertebrates. However, its gene order is different from other vertebrates (except for C. myriaster). The Cytb gene, tRNA^Thr and the control region are located between the ND5 gene and the ND6 gene in C. japonicus while they are between the ND6 gene and the tRNA^Phe gene in other vertebrates. The same gene order also appeared in C. myriaster. The mitochondrial genome of C. japonicus and C. myriaster, which are currently the only two members of Conger genus with complete mitochondrial genome, appeared in the gene rearrangement, so we speculated that the mitochondrial genome of all species from Conger genus may appear in the gene rearrangement. However, to clarify the speculation, more mitochondrial genomes of Conger genus will be needed in the future. In addition, phylogenetic analysis result demonstrated that C. japonicus and C. myriaster clustered in a clade and formed a sister relationship.