Characterization of the Complete Mitochondrial Genome of Bellamya limnophila and Its Phylogenetic Status Within Viviparidae

Bellamya limnophila is a mollusk of significant medical and economic value in China. Understanding the complete mitochondrial genome of this species will better establish a foundation for systematic classification research on Viviparidae. Therefore, we sequenced the complete mitochondrial genome of B. limnophila, conducted a comprehensive analysis of its structural characteristics, and constructed a phylogenetic tree using maximum likelihood and Bayesian methods. The results showed that the genome sequence is 16,991 bp in length, including 13 protein-coding genes (PCGs), 20 transfer RNA genes (tRNAs), 2 ribosomal RNA genes (rRNAs), and 1 non-coding region (D-loop). In summary, the Ka/Ks ratios of all PCGs were <1, indicating that purifying selection dominated the evolutionary process of these snails. The entire genome structure exhibited conservative features, such as the majority of start codons being the standard ATG codon and the majority of tRNA genes having the standard cloverleaf secondary structure. B. limnophila and B. quadrata showed collinearity in terms of sequence homology. Phylogenetic analysis indicates that the clade formed by the genera Margarya, Cipangopaludina, and Bellamya is the sister group of the genus Viviparus; Bellamya limnophila is more closely related to B. quadrata than to other species. This study contributes to the mitochondrial genome database of the family Viviparidae and provides valuable insights into the phylogenetic relationships of related snails.