Comparative mitogenomic analyses unveil conserved and variable mitogenomic features and phylogeny of Chedrinae fish

Chedrinae fish, which belong to Danionidae, have important ornamental, economic, and scientific value. At present, however, their mitogenomic features are unclear and their phylogenetic relationships remain controversial. In this study, we presented five new Chedrinae mitochondrial genomes (mitogenomes) and analyzed the conserved and variable mitogenomic characteristics of 17 Chedrinae fish. The gene composition and arrangement and secondary structure of transfer RNAs (tRNAs) were highly conserved among the Chedrinae mitogenomes. However, the length of the control region and base composition were variable. Interestingly, the mitogenome of Barilius barila was unusual, with lower A+T content in the first codon of protein-coding genes (PCGs) (47.32% versus average of 54.47%) and distinct pattern of codons per thousand codons (CDspT). Three Chedrinae fish had a long tandem repeat (>291 bp) in the 5'-end of the control region, which may increase their adaptability. In addition, tRNA^Lys had notably larger DHU and TΨC loops than other tRNAs. The phylogenetic trees of the Chedrinae fish suggested that the Barilius genus was not a monophyletic group but could be divided into two main groups based on significant differences in A+T content. This study provides insights into the mitogenomic features and phylogenetic implications of Chedrinae fish, which should benefit their systematics and conservation.