Abstract
First-instar juveniles of six caprellid amphipods of the genus Caprella are described based on specimens collected from the Pacific coast of southern Hokkaido, Japan: Caprella acanthogaster Mayer, 1890, C.alaskana Mayer, 1903, C.bispinosa Mayer, 1890, C.cristibrachium Mayer, 1903, C.mixta Mayer, 1903, and C.mutica Schurin, 1935. Morphological characters of the juveniles are compared with those of the previously described juveniles of six other species distributed along the northern coasts of Japan. We newly identified traits of the flagellum of antenna 1 and the seta at the base of the gill as diagnostic characters for species discrimination among the 12 species. This study makes it possible to identify first-instar juveniles of the 12 species of Caprella occurring in northern Japan.
