Genetic and morphological separation of Uca occidentalis, a new East African fiddler crab species, from Uca annulipes (H. Milne Edward, 1837) (Crustacea: Decapoda: Brachyura: Ocypodidae)

The fiddler crab Uca annulipes (Milne Edwards, 1837) is thought to be widely distributed in the Indo-West Pacific. Previous studies showed consistent morphological differences between East African populations and those from the eastern Indian Ocean and Western Pacific. Here we provide detailed comparisons of the morphology and DNA sequences corresponding to the mitochondrial 16S rRNA gene fragment. As consequence, we refer to the populations from the western Indian Ocean as a new species, Uca occidentalis n. sp., whereas Uca annulipes has wide-ranging populations in the eastern Indian Ocean and West Pacific. The new species can be distinguished from U. annulipes by consistent morphological characters, including male first gonopods and male minor cheliped, which is supported by molecular evidence.