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An assessment of the global freshwater crab diversity is presented. A total of 1,476 species in 14 families are currently known from all zoogeographical regions (except Antarctica), including 1,306 species in eight exclusively freshwater families (Pseudothelphusidae, Trichodactylidae, Potamonautidae, Deckeniidae, Platythelphusidae, Potamidae, Gecarcinucidae and Parathelphusidae). Estimates of true freshwater crab diversity including likely numbers of undescribed taxa suggest that the field remains largely in a “discovery” phase. Main ideas on the origins, diversification, and phylogeny of true freshwater crabs are briefly discussed. The economic importance of freshwater crabs is also highlighted.

The apparent biotic affinities between the mainland and the island in the Western Ghats-Sri Lanka biodiversity hotspot have been interpreted as the result of frequent migrations during recent periods of low sea level. We show, using molecular phylogenies of two invertebrate and four vertebrate groups, that biotic interchange between these areas has been much more limited than hitherto assumed. Despite several extended periods of land connection during the past 500,000 years, Sri Lanka has maintained a fauna that is largely distinct from that of the Indian mainland. Future conservation programs for the subcontinent should take into account such patterns of local endemism at the finest scale at which they may occur.

Recent explorations of caves in Pahang, central Peninsular Malaysia yielded specimens of an unusual long-legged terrestrial, cave-dwelling crab. Morphological examinations of the specimens collected, in comparison with known species from the region suggests that they belong to a new genus and species, which are described herein. Merapohra karsticola gen. nov. et sp. nov ., is differentiated from other potamids by characters of the carapace epigastric and postorbital cristae, ambulatory legs, male thoracic sternum, male pleon, and diagnostic structure of the male first gonopod. The discovery of this new genus and species of cave-dwelling crab highlights the importance and high diversity of karst systems in Peninsular Malaysia, which are imperilled in light of ongoing quarrying and mining activities.

The looming mass extinction of biodiversity in the humid tropics is a major concern for the future, yet most reports of extinctions in these regions are anecdotal or conjectural, with a scarcity of robust, broad-based empirical data. Here we report on local extinctions among a wide range of terrestrial and freshwater taxa from Singapore (540 km2) in relation to habitat loss exceeding 95% over 183 years. Substantial rates of documented and inferred extinctions were found, especially for forest specialists, with the greatest proportion of extinct taxa (34-87%) in butterflies, fish, birds and mammals. Observed extinctions were generally fewer, but inferred losses often higher, in vascular plants, phasmids, decapods, amphibians and reptiles (5-80%). Forest reserves comprising only 0.25% of Singapore's area now harbour over 50% of the residual native biodiversity. Extrapolations of the observed and inferred local extinction data, using a calibrated species-area model, imply that the current unprecedented rate of habitat destruction in Southeast Asia will result in the loss of 13-42% of regional populations over the next century, at least half of which will represent global species extinctions.

The systematics of four species of the homolodromiid genus A. Milne-Edwards, 1880, from East Asia and the Philippines is reappraised: Ng & McLay, 2005, Ortmann, 1892, Guinot, 1993, and Guinot, 1995; and key characters such as the epistome, gonopods, and spermatheca are figured in detail. Two new species, and , are described from Taiwan and the Philippines, respectively. resembles Guinot, 1995, and Ahyong, 2008 (from New Caledonia and New Zealand) but can be separated by its distinctly spinulated carapace surfaces and proportionately shorter fifth ambulatory legs. is superficially similar to (Alcock & Anderson, 1899) and Guinot, 1993, but can easily be separated by possessing a broad dorsoventrally flattened infraorbital tooth. A genetic study of the species using the mitochondrial cytochrome c oxidase I gene confirms that the taxa are distinct, with coming out in a well-supported clade from congeners. The megalopa of is also reported for the first time.

The leucosiid crab Orientotlos iishibai Sakai, 1980 was described from one female collected off western Japan and had never been reported since. The species is now recorded from southwestern Taiwan for the first time, and is redescribed and figured at length. Although Sakai argued that Orientotlos Sakai, 1980, is closely related to Oreophorus Rüppell, 1830 and Atlantotlos Doflein, 1904, the genus is actually morphologically most similar to Merocryptus A. Milne-Edwards, 1873. The two genera, however, still differ markedly in a number of key carapace and cheliped characters.

A new species of semiterrestrial freshwater crab is described from Tapah Hills in Peninsular Malaysia. Geosesarma wongi sp. nov. is the 13 th member of the genus reported from the country and is most similar to G. peraccae (Nobili, 1903) and G. cataracta Ng, 1986, but easily separated by its distinct carapace features and structures of the adult male chela and male first gonopod. The types of G. peraccae are figured for the first time. Geosesarma cataracta is also figured in detail, and the type series is shown to be mixed.

Abstract The identity of the poorly known plagusiid crab Euchirograpsus polyodous (Stebbing, 1921) is clarified on the basis of a good series of specimens from Zanzibar. The species proves to be a senior synonym of Euchirograpsus madagascariensis Türkay, 1978. The species is characterized by the more elongate and rugose third maxillipeds, distinctly serrate flexor margins of the second and third ambulatory legs, presence of only five major pairs of corneous setae on the ambulatory dactylus, and structure of the male first gonopod. The holotype of Euchirograpsus madagascariensis Türkay, 1978, is here designated as the neotype of Pachygrapsus polyodous Stebbing, 1921, making both names objective synonyms. A key to the nine species of Euchirograpsus is provided.

Abstract A previously unreported collection of small goneplacid crabs from Indonesia and Australia belonging to Raoul Sèrene and Kasim Moosa is documented herein. Five taxa are reported, including a new species and genus, Kingelus kasimi gen. et sp. nov., from the Moluccas, Indonesia. The new genus differs markedly from allied genera like Carcinoplax, Pycnoplax and Menoplax by its distinctive carapace and gonopod morphology. The range of Pedroplax megalops (Takeda, 1989) is also extended to Indonesia and the Philippines, with Paragoneplax serenei (Zarenkov, 1972) being a new Australian record.

DNA barcoding and DNA taxonomy have recently been proposed as solutions to the crisis of taxonomy and received significant attention from scientific journals, grant agencies, natural history museums, and mainstream media. Here, we test two key claims of molecular taxonomy using 1333 mitochondrial COI sequences for 449 species of Diptera. We investigate whether sequences can be used for species identification (“DNA barcoding”) and find a relatively low success rate (< 70%) based on tree-based and newly proposed species identification criteria. Misidentifications are due to wide overlap between intra- and interspecific genetic variability, which causes 6.5% of all query sequences to have allospecific or a mixture of allo- and conspecific (3.6%) best-matching barcodes. Even when two COI sequences are identical, there is a 6% chance that they belong to different species. We also find that 21% of all species lack unique barcodes when consensus sequences of all conspecific sequences are used. Lastly, we test whether DNA sequences yield an unambiguous species-level taxonomy when sequence profiles are assembled based on pairwise distance thresholds. We find many sequence triplets for which two of the three pairwise distances remain below the threshold, whereas the third exceeds it; i.e., it is impossible to consistently delimit species based on pairwise distances. Furthermore, for species profiles based on a 3% threshold, only 47% of all profiles are consistent with currently accepted species limits, 20% contain more than one species, and 33% only some sequences from one species; i.e., adopting such a DNA taxonomy would require the redescription of a large proportion of the known species, thus worsening the taxonomic impediment. We conclude with an outlook on the prospects of obtaining complete barcode databases and the future use of DNA sequences in a modern integrative taxonomy.