Complete Mitochondrial Genomes of Four Strains and Comparison with Other Trionychidae Species.

The Chinese soft-shelled turtle () is an important aquaculture reptile with rich nutritional and medicinal values. In recent decades, the wild resources of have been depleting due to natural and artificial factors. Herein, we report the complete mitochondrial genome of four strains, including the Japanese (RB) strain, Qingxi Huabie (HB) strain, Jiangxi (JB) strain, and Qingxi Wubie (WB) strain. The nucleotide composition within the complete mitogenomes was biased towards A + T with a variable frequency ranging from 59.28% () to 70.31% (). The mitogenomes of all four strains contained 13 protein-coding genes (PCGs), 22 tRNAs, 2 rRNAs, 1 control region, and a replication origin region of the L-strand replication (OL), which was consistent with most vertebrates. Additionally, the , , , and genes possessed high genetic variation and can be used as potential markers for the identification of these strains. Additionally, all PCGs genes were evolving primarily under purifying selection. Through comparative analysis, it was revealed that most of the tRNAs were structurally different in the TψC stem, DHU stem, and acceptor stem. The length of the tandem repeats in the control region was variable in the four strains, ranging from 2 bp to 50 bp. Phylogenetic analysis indicated that all strains clustered into one branch and were closely related to other Trionychinae species. Overall, this study provides mitochondrial genome information for different strains to support further species identification and germplasm resource conservation.