Sequencing of the Complete Mitochondrial Genome of the Big Brown Mactra Clam, (Venerida: Mactridae).

Mitochondrial genomes are playing an increasingly important role in molluscan taxonomy, germplasm, and evolution studies. The first complete mitochondrial genome of the commercial big brown mactra clam, , was characterized using Illumina next-generation sequencing in this study. The 17,289 bp circular genome has a typical gene organization of 13 protein-coding genes (PCGs), 2 rRNAs, and 22 tRNAs, with an obvious (A + T)-bias of 64.54%. All PCGs exhibited a homogeneous bias in nucleotide composition with a (A + T)-bias, a positive GC skew, and a negative AT skew. Results of phylogenetic analysis showed that was most closely related to . The functional gene arrangement of the two species was identical but different from other species. The congeneric relationships among species were demonstrated by genetic distance analysis. Additionally, the selective pressure analysis suggested that was highly efficient for discriminating closely related species in genus , while was the most appropriate marker for population genetic analysis.