Mitochondrial rearrangement and adaptive evolution in whale lice (Amphipoda): molecular signatures of obligate parasitism

In this study, we performed molecular identification and complete mitogenome annotation of the whale lice ( Cyamus boopis Lütken, 1870) collected from the skin of a humpback whale stranded on the coast of the East China Sea. The specimens were identified as C. boopis based on specific morphological characteristics. These features include a dorsoventrally flattened body lacking appendages adapted for swimming, robust thoracic pereopods with sharply incurved terminal hooks, prominent tubular respiratory gills on both sides of the thorax, and distinct sexual dimorphism. The complete mitogenome of this parasite is 15,311 bp in length and contains 37 genes (13 protein coding genes, 22 transfer RNAs, two ribosomal RNAs), together with a putative control region located between trnP and trnI . This study represents the first characterization of the complete mitogenome of C. boopis. These findings provide molecular validation for the distinct taxonomic status of this species and lay a foundation for the future identification of closely related species within the family Cyamidae. The data generated in this study constitute an essential molecular reference for investigating the phylogeny, genomic evolution, and coevolutionary relationships between hosts and parasites in obligate ectoparasitic crustaceans.