Evolutionary relationships among American mud crabs (Crustacea: Decapoda: Brachyura: Xanthoidea) inferred from nuclear and mitochondrial markers,with comments on adult morphology

Members of the brachyuran crab superfamily Xanthoidea sensu Ng, Guinot & Davie (2008) are a morphologically and ecologically diverse assemblage encompassing more than 780 nominal species. On the basis of morphology, Xanthoidea is presently regarded to represent three families: Xanthidae, Pseudorhombilidae, and Panopeidae. However, few studies have examined this superfamily using modern phylogenetic methods, despite the ecological and economic importance of this large, poorly understood group. In this study we examine phylogenetic relationships within the superfamily Xanthoidea using three mitochondrial markers, 12S rRNA, 16S rRNA, and cytochrome oxidase I (COI), and three nuclear markers, 18S rRNA, enolase (ENO) and histone H3 (H3). Bayesian and maximum‐likelihood analyses indicate that the superfamily Xanthoidea is monophyletic; however, the families Xanthidae, Panopeidae, and Pseudorhombilidae, as defined by Ng et al., are not, and their representative memberships must be redefined. To this end, some relevant morphological characters are discussed. © 2013 The Linnean Society of London     

Morphological and genetic differentiation between populations of river crabs (Decapoda: Potamonautidae) from the Western Gape, South Africa, with a taxonomic re-examination of Gecarcinautes brincki

As part of a larger study on the systematics of river crabs of the family Potamonautidae in southern Africa, several populations of potamonautid crabs were collected from the Cape Peninsula and surrounds, Western Cape. Two species were represented: Gecarcinautes brincki and Potamonautes perlatus. The structure of the mandibular palp in the eight populations of G. brincki examined was variable, and in four populations, the structure of this palp was the same as that which can be found in species of Potamonautes. This paper re-examines the taxonomic status of G. brincki , quantifies the morphological and genetic differentiation between populations of G. brincki and P. perlatus from the Cape Peninsula, and determines the extent of morphological and genetic differentiation among geographically separated populations of G. brincki. Examination of type and other material confirmed that Gecarcinautes brincki conforms to the current diagnosis of the genus Potamonautes (family Potamonautidae) to which it is therefore transferred. Discriminant functions analysis and protein gel electrophoresis showed that P. perlatus and P. brincki are morphometrically and genetically distinct, with the three P. perlatus populations separating from the six P. brincki populations at a genetic identity value of I = 0.66 (D = 0.419). The results also showed that P. brincki is a highly structured entity, with die populations collected from the Cape Peninsula clearly separating both genetically (I = 0.75, corresponding to D = 0.296), and morphologically (presence or absence of a flange on the terminal segment of the mandibular palp) from those collected further east. The lack of gene flow between populations of this species is discussed in the light of current species concepts.     

A first record of anchialine crab of the genus Orcovita Ng and Tomascik, 1994 (Decapoda: Brachyura: Varunidae) from Japan, with description of the species

Orcovita miruku, new species, is described from Ishigaki Island, southern Ryukyu Islands, Japan. Orcovita miruku is easily distinguished from the other congeners by the presence of three teeth (including external orbital angle) on the anterolateral margin of the carapace. Orcovita angulata may be allied to O. miruku, but there are a number of differences in the characters of the carapace and the ambulatory legs. The holotype, obtained from an anchiline pool in a limestone excavation, is the only specimen collected thus far, and this is the first record of an anchiline crab from Japan.