A new species of Athelges (Crustacea, Isopoda, Epicaridea, Bopyridae) from Japan, with morphological and DNA barcode data

<i>Athelges pileus</i> <b>sp. nov</b>. is described as an abdominal bopyrid of the hermit crab <i>Diogenes edwardsii</i> collected from the Noto Peninsula, Japan. <i>Athelges pileus</i> <b>sp. nov</b>. is distinguished from its congeners by the following combination of characters. Female: head deeply sunk in thorax, anterolateral margin of head with pair of notches; anterior margin of frontal lamina concave; merus of pereopod 1 with broad and long projection ventrally; pereopods 5 and 6 with large gap between them; pleomeres 1-4 each with subovate biramous pleopods; each pleopod with peduncle, becoming smaller posteriorly; pleotelson with mushroom-shaped end. Male: pleon subovate with anal cone distally. The present species is the 14^th member of the genus <i>Athelges</i>, and the second species from Asia. This is the second species of <i>Athelges</i> infesting <i>Diogenes edwardsii</i>. We also provide a partial sequence of the mitochondrial cytochrome c oxidase subunit 1 (COI) gene (658 bp), mitochondrial 16S rRNA gene (482 bp), and nuclear 18S rRNA (724 bp) as a DNA barcode for the species. We show by molecular phylogenetic analysis that the present species is distinct from <i>A. takanoshimensis</i>.