A review of the mud crab genus Pseudohelice Sakai, Türkay & Yang, 2006 (Crustacea: Brachyura: Varunidae), with redescription of Cyclograpsus latreillii H. Milne Edwards, 1837, from the western Indian Ocean

Members of the genus Pseudohelice Sakai, Türkay & Yang, 2006 (family Varunidae) inhabit estuaries and high intertidal zone with sediments composed of mud and sand in tropical to temperate regions. Previous studies showed only one species, Pseudohelice subquadrata (Dana, 1851) in this genus, with a wide distribution in the Indo-West Pacific. In the present study, the species from the western Indian Ocean is shown to be a valid species, Pseudohelice latreillii (H. Milne Edwards, 1837), based on morphological and molecular evidence. The latter species had previously been incorrectly synonymised with Helice tridens (De Haan, 1835). The two species are very similar to each other in morphology, but can be distinguished by a suite of characters, including the structures of the infraorbital ridges in both sexes, male gonopods 1 and female vulvae. Based on the molecular evidence from cytochrome oxidase subunit 1 (COI), P. subquadrata and P. latreillii form two well-supported clades, and the intraspecific and interspecific divergences of COI are 0–1.9% and 3.3%–5.1%, respectively. Geographically, P. subquadrata is distributed in the western Pacific while P. latreillii occurs in the western Indian Ocean.