Complete Mitochondrial Genomes of Polydactylus macrochir (Günther, 1867): Genome Characterization and Phylogenetic Analysis

Polydactylus macrochir (Günther, 1867) is a number of family Polynemidae. The placement of the Polynemidae among teleosts has varied over the years. Therefore, in this study we sequenced the complete mitochondrial genome of P. macrochir, analyzed the characterization of the mito-chondrial genome, and investigated the phylogenetic relationships of Polynemidae. The lengths of the P. macrochir mitogenomes was 16,738 bp with the typical order. Nucleotide composition analysis showed that P. macrochir mitogenome was AT biased (54.15%), and the PCGs tended to use A and C than T and G at the third codon. All the PCGs started with the regular codon ATG, except for the cox1 which started with GTG. The termination codon varied across PCGs. It was shown that the ka/ks ratios of all PCGs were less than 1. The phylogenetic analysis, based on the maximum likelihood (ML) and Bayesian inference (BI) methods, indicated that 8 Threadfins spe-cies formed a well-supported monophyletic cluster. Polynemidae and Sphyraenidae clustered together as a monophyletic group. According to TimeTree analyses, the most recent common ancestor (MRCA) of Polynemidae was traced back to about 52.81 million years ago (MYA), while 6 species within Polynemidae diverged from 11.70 MYA to 20.05 MYA. The present study provides valuable mitochondrial information for the classiffcation of P. macrochir and new insights in phylogenetic relationships of Polynemidae.