Complete Mitochondrial Genomes of Magallana Saidii (Wong & Sigwart, 2021) From Malaysia and Phylogenetic Insight

Magallana saidii (Wong & Sigwart, 2021), locally known as the white oyster, is an oyster species endemic to the Muar River, Johor, Malaysia. Although long recognized and exploited by local fishers, it has not been reported elsewhere, making it of conservation concern due to its restricted distribution. Despite its ecological and economic importance, M. saidii has received limited molecular attention since its recent taxonomic description. In this study, two complete mitochondrial genomes (mitogenomes) of M. saidii from Muar, Johor are presented. Whole-genome sequencing was performed using the Illumina NovaSeq6000 platform, and the mitochondrial contigs were assembled using a de novo approach. The mitogenomes measured 21,499 bp (PV711311) and 21,505 bp (PV711312) in length. Each mitogenome comprised 38 genes, including 13 protein-coding genes, 23 transfer RNAs, and two ribosomal RNAs, with largely conserved gene arrangement. Notably, the atp8 gene, which is often unresolved in oyster mitogenomes, was clearly identified. The mitogenome exhibited a strong adenine and thymine bias (A+T content of 66.3%), with nucleotide compositions of 37.3% thymine, 29.0% adenine, 20.6% guanine and 13.0% cytosine. Maximum likelihood phylogenetic analysis based on 13 concatenated protein-coding genes recovered M. saidii as a well-supported clade with another M. saidii mitogenome from GenBank (accession PV564049), and as sister to a clade comprising M. nippona, M. hongkongensis, and M. ariakensis. The complete mitogenome of M. saidii provides a valuable genetic reference to support future phylogenetic studies and conservation management of oysters in Malaysia.