Novel Gene Rearrangement and the Complete Mitochondrial Genome of Cynoglossus monopus: Insights into the Envolution of the Family Cynoglossidae (Pleuronectiformes)

Cynoglossus monopus, a small benthic fish, belongs to the Cynoglossidae, Pleuronectiformes. It was rarely studied due to its low abundance and cryptical lifestyle. In order to understand the mitochondrial genome and the phylogeny in Cynoglossidae, the complete mitogenome of C. monopus has been sequenced and analyzed for the first time. The total length is 16,425 bp, typically containing 37 genes with novel gene rearrangements. The tRNA-Gln gene is inverted from the light to the heavy strand and translocated from the downstream of tRNA-Ile gene to its upstream. The control region (CR) translocated downstream to the 3’-end of ND1 gene adjoining to inverted to tRNA-Gln and left a 24 bp trace fragment in the original position. The phylogenetic trees were reconstructed by Bayesian inference (BI) and maximum likelihood (ML) methods based on the mitogenomic data of 32 tonguefish species and two outgroups. The results support the idea that Cynoglossidae is a monophyletic group and indicate that C. monopus has the closest phylogenetic relationship with C. puncticeps. By combining fossil records and mitogenome data, the time-calibrated evolutionary tree of families Cynoglossidae and Soleidae was firstly presented, and it was indicated that Cynoglossidae and Soleidae were differentiated from each other during Paleogene, and the evolutionary process of family Cynoglossidae covered the Quaternary, Neogene and Paleogene periods.