First insights into the complete mitochondrial genome of a deep-sea eel Congriscus megastoma (Anguilliformes, Congroidei, Congridae): characterization and phylogenetic inference

The complete mitochondrial DNA sequence of a deep-sea eel Congriscus megastoma (Anguilliformes: Congridae) was determined by high throughput sequencing technology. As the first mitogenome of the genus Congriscus up to now, its entire mtDNA sequence was 17,616 bp in length, including 37 mitochondrial genes (13 protein-coding genes, 2 rRNA genes, 22 tRNA genes) and 2 control regions, which was inconsistent with that of the typical vertebrate mitogenomes. In addition, the genes of C. megastoma exhibited an obvious rearrangement. ND6 and tRNA-Glu were transferred between tRNA-Thr and tRNA-Pro, as well as a doubled control region appeared. The tandem duplication-random loss (TDRL) model was an ideal explanation for this irregular gene reorganization phenomenon. The Bayesian phylogenetic tree showed that Congridae species were divided into four clades, suggesting their non-monophyletic origin. Congriscus had the closest relationships with Thalassenchelys and Coloconger. Species with gene rearrangement separately clustered as one clade. The results provided a basis for future studies of mitochondrial DNA structure and phylogeny of Anguilliformes.