The complete mitogenome of <i>Calappa japonica</i> ortmann, 1892 (Decapoda: Calappidae) from the East China Sea

This study presents the first complete mitochondrial genome of Calappa japonica Ortmann, 1892, the fourth genetic resource for the family Calappidae. Its mitogenome (GenBank: PX866701) is 15,773 bp in length and comprises 13 protein-coding genes (PCGs), two rRNA genes, 22 tRNA genes, and one control region (D-loop). Nucleotide composition analysis showed a high AT content (69.3%), with adenine (34.5%) and thymine (34.8%) dominating. Phylogenetic analysis grouped C. japonica with C. granulata and C. rissoana in a monophyletic clade, with C. bilineata as the sister to this clade. This work provides mitochondrial genomic resources for future studies on Calappidae systematics and species identification.