Jesogammarus (Jesogammarus) acalceolus sp. nov., male (7.4 mm), NSMT-Cr 29003 A habitus, lateral view B–D dorsal margins of pleonites 1–3, respectively, dorsal views E–G dorsal margins of urosomites 1–3, respectively, dorsal views H peduncular articles 1–3, accessory flagellum, and flagellar articles 1–4 of antenna 1, medial view I aesthetasc and associate setae on the flagellum of antenna 1, medial view J peduncular articles 1–5 and flagellar articles 1–3 of antenna 2, medial view K upper lip, posterior view L right mandible, medial view M–N incisor and lacinia mobilis of left and right mandibles, medial views O lower lip, ventral view P maxilla 1, medial view Q serrate robust setae on outer plate of maxilla 1, medial view.

  Part of: Tomikawa K, Kimura N (2021) On the brink of extinction: a new freshwater amphipod Jesogammarus acalceolus (Anisogammaridae) from Japan. ZooKeys 1065: 81-100.