First determination and analysis of the complete mitochondrial genome of X-ray tetra (Ulrey, 1894) (Actinopteri, Characidae).

The complete mitochondrial genome of the X-ray tetra (, Ulrey, 1894) was determined by using next-generation sequencing technology, and its mitochondrial genome characteristics were analyzed. The sequence total length was 16,753 bp, and the A + T content was 57.44%. The position and composition of the 37 genes were consistent with those of other Characidae species in this family. There are 13 protein-coding genes, 22 tRNA genes, two rRNA genes, and one control region. Except for and , which use ATT and GTG as start codons, respectively, all other protein-coding genes use ATG as the start codon. uses AGG as the stop codon; and use incomplete TA as the stop codon; and use incomplete T as the stop codon; uses TAG as the stop codon, and the other seven protein-coding genes use TAA as the stop codon. Based on the concatenated nucleotide sequences of 13 protein-coding genes from 18 Characidae species, phylogenetic analysis revealed that belongs to the family Characidae and is most closely related to Determining the mitogenomes of improves our understanding of the phylogeny and evolution of Characidae.