Comparative Mitogenomic Analysis of Two Snake Eels Reveals Irregular Gene Rearrangement and Phylogenetic Implications of Ophichthidae.

Simple Summary: It is generally known that the order of mitochondrial genes is highly conserved, but to date, along with the gradual increase of teleostean mtDNA sequences in the GenBank database, the gene rearrangement events have been identified in all the published complete mitogenomes of Ophichthidae species. This amusing finding makes it necessary to carry out studies on mitogenome characteristics and phylogenetic evolution of this fish group. Here, we chose Ophichthus evermanni and O. erabo as representatives, and obtained the whole mtDNA sequences using the Illumina high-throughput sequencing technology. The novel gene rearrangement and phylogenetic relationships indicated that Ophichthidae might be a monophyletic group and formed a sister group with Muraenesocidae. The family Ophichthidae has the largest number and the most various species (about 359 valid species) in the order Anguilliformes worldwide. Both morphological and molecular characteristics have been used to assess their taxonomic status. However, due to the ambiguous morphological features, molecular data such as mitochondrial DNA sequences have been implemented for the correct identification and classification of these fishes. In this study, the gene arrangement and structure characteristics of two Ophichthidae mitochondrial genomes were investigated for the first time. The total mitogenome lengths of O. evermanni and O. erabo were 17,759 bp and 17,856 bp, respectively. Comparing with the ancestral mitochondrial gene order, the irregular gene rearrangement happened between ND6 and tRNA-Pro (P) genes with another similar control region emerging between tRNA-Thr (T) and ND6 genes, which could be explained by the tandem duplication and random loss (TDRL) model appropriately. ML phylogenetic tree demonstrated that the family Ophichthidae was monophyletic origin, but genus Ophichthus might be polyphyletic because of the confused cluster relationships among different species. [ABSTRACT FROM AUTHOR]