ON THE IDENTITY OF THE INDO-WEST PACIFIC LITTORAL XANTHID CRAB, LEPTODIUS EXARATUS (H. MILNE EDWARDS, 1834) (CRUSTACEA: DECAPODA: BRACHYURA: XANTHIDAE)

The xanthid crab Leptodius exaratus (H. Milne Edwards, 1834) has been widely reported from the Indo-West Pacific, where it is a ubiquitous component of the intertidal and shallow subtidal fauna. The taxonomy of this species, however, is complex and there are many synonyms, most of which have not been adequately treated or discussed in the past. A close examination of a series of specimens throughout its range shows that L. exaratus should be restricted to the western Indian Ocean. Populations from the eastern Indian and western Pacific oceans should be referred to Leptodius affinis (De Haan, 1835), a species originally described from Japan. While their carapaces are superficially similar, the male first gonopod structure is a reliable character to distinguish these two species. Cancer (Xantho) lividus De Haan, 1835, Leptodius nigromaculatus Serene, 1962, as well as some of the varieties of L. exaratus established by Stimpson (1907), are considered to be junior subjective synonyms of L. affinis (De Haan, 1835). Where necessary, lectotypes or neotypes are designated to stabilise the taxonomy of the two species treated herein.