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Freshwater crabs play essential roles in the well-functioning of the inland aquatic ecosystems. However, due to the lack of sufficient molecular resources, the study of freshwater crabs has been greatly hindered. In this study, the mitochondrial genome of Huananpotamon koatenense, a freshwater crab endemic to China, was sequenced for the first time. This mitogenome sequence is 15,528 bp long, and contains 13 protein-coding genes, 2 rRNA genes and 22 tRNA genes. Phylogenetic analyses based on 25 mitogenomes showed that H. koatenense was clustered with the known congeneric species of H. lichuanense. [ABSTRACT FROM AUTHOR]

The taxonomy of the potamiscine freshwater crab genus Tenuipotamon Dai, 1990, which contains seven species, is revised. According to a concurrent molecular phylogenetic study, Tenuipotamon is paraphyletic, and is composed of two lineages. In this study, Tenuipotamon sensu stricto is restricted to its type species, T. purpura Dai, 1990, while a new genus, Pusillamon gen. nov. , is established to accommodate the remaining six species placed previously in Tenuipotamon sensu stricto (T. baishuiense Chen, 1993, T. huaningense Dai & Bo, 1994, T. panxiense Chen, 1993, T. tonghaiense Chen, 1993, T. xinpingense Chen, 1993, and T. yuxiense Chen, 1993). Diagnoses are provided for the two genera, which are both endemic to the topographically complex Hengduan Mountains Region of southwestern China. [ABSTRACT FROM AUTHOR]

The taxonomy of the potamid crab genus Parvuspotamon Dai & Bo, 1994, with two species native to Yunnan province of southwest China, is revised based on morphological and molecular data. In order to stabilise the taxonomy of these species (and the genus), two separate genera are hereby designated: Parvuspotamon and Songpotamon gen. nov. While Parvuspotamon is restricted to P. yuxiense Dai & Bo, 1994, as a monotypic genus, P. dixuense Naruse, Chia & Zhou, 2018, is transferred to a new genus, Songpotamon gen. nov. In addition, two new species of Songpotamon gen. nov. are described herein: S. funingense sp. nov. and S. malipoense sp. nov. Songpotamon gen. nov. morphologically most resembles Parvuspotamon and Chinapotamon Dai & Naiyanetr, 1994, but can be distinguished by the combination of characters in the carapace, third maxilliped, thoracic sternites, and male first gonopod. The genetic data derived from the mitochondrial 16S rDNA also supports the monophyly of these new taxa. [ABSTRACT FROM AUTHOR]

A new species of freshwater crab of the genus Isolapotamon Bott, 1968 (Potamidae) is described from western Sabah in Malaysian Borneo. Isolapotamon seowi new species, is the sixth species of Isolapotamon known from Sabah, and differs from its closest congener, I. buntyae Ng, Low & Clark, 2022, from eastern Borneo, in possessing a relatively lower carapace, a more rugose dorsal carapace surface, the postorbital cristae being sharper and subparallel with the frontal margin, relatively shorter fourth ambulatory legs, and the terminal segment of the male first gonopod is gently curved with the subdistal process slightly longer than the distal projection and angled at 90° to the longitudinal axis. [ABSTRACT FROM AUTHOR]

The confused and intertwined identities and taxonomic histories of three Asian freshwater crab genera, Potamiscus Alcock, 1909, Ranguna Bott, 1966, and Dromothelphusa Naiyanetr, 1992, are reviewed and clarified. Ranguna, long assumed to be a junior synonym of Potamiscus (itself, until 2003, considered a junior synonym of Potamon Savigny, 1816), is recognised here as a valid genus, with the sole representative, Ranguna rangoonensis (Rathbun, 1904), shown to differ from Potamiscus species by carapace, third maxilliped, male thoracic sternal, male pleon and gonopod structures. Potamon (Potamiscus) decourcyi Kemp, 1913, is also transferred to Ranguna. The only known species of Dromothelphusa (originally established to replace Ranguna), D. longipes (A. Milne-Edwards, 1869), is known mostly from very old and dried museum material and treated here in detail based on fresh-collected adult male specimens. The three genera are rediagnosed and illustrated in detail. [ABSTRACT FROM AUTHOR]

Four species of Chinese potamid freshwater crabs currently placed in Eosamon Yeo & Ng, 2007 are assigned to a new genus, Aiyunamon. While the new genus is morphologically close to Eosamon, Indochinamon Yeo & Ng, 2007, and Doimon Yeo & Ng, 2007, it possesses a distinctive combination of carapace, male pleon, male first gonopod, and vulva characters that easily distinguishes it. This distinction is supported by genetic data. The new genus is described and compared with allied genera. Eosamon species are now restricted to Indochina. [ABSTRACT FROM AUTHOR]

A new genus Ruiyupotamon gen. nov. and four new species, R. banqiaopingense sp. nov., R. zhongjiangense sp. nov., R. jinjiangense sp. nov., and R. zhongyiense sp. nov. belonging to the subfamily Potamiscinae (Potamidae), collected from northwestern Yunnan Province, P.R. China, are described. Molecular phylogenetic data derived from both mitochondrial (16S), and nuclear (28S and ITS2) markers supports the establishment of the new genus and four new species. Résumé: Un nouveau genre Ruiyupotamo nov. gen. et quatre nouvelles espèces, R. banqiaopingense nov. sp., R. zhongjiangense nov. sp., R. jinjiangense nov. sp. et R. zhongyiense nov. sp. Appartenant à la sous famille des Potamiscinae (Potamidae), récoltés dans le nord ouest de la province du Yunnan, R.p. de Chine, ont été décrits. Les données de phylogénie moléculaire proviennent à la fois de marqueurs mitochondriaux (16S) et nucléaires (28S et ITS2) supportent l'établissement du nouveau genre et des quatre nouvelles espèces. [ABSTRACT FROM AUTHOR]

Two new species of potamid crabs, Eosamon daiae sp. nov. and Indochinamon malipoense sp. nov. are described from the Sino-Burmese border, southwestern Yunnan and from the Sino-Vietnamese border, southeastern Yunnan, China. The two new species can be distinguished from their closest congeners by several characters, among which is the form of the first gonopod structures. Molecular analyses based on partial mitochondrial 16S rDNA sequences also support the systematic status of these new taxa. [ABSTRACT FROM AUTHOR]

The identity of the potamid freshwater crab, Indochinamon manipurense (Alcock, 1909) from the state of Manipur in northeast India, is clarified based on an examination of the type specimens. The species is redescribed and a lectotype designated. Specimens from the same region previously referred to this species were compared to the types of I. manipurense and shown to belong to a new species of Potamiscus Alcock, 1909, instead. The new species, Potamiscus takedai sp. nov., can easily be separated from I. manipurense by the characters in the carapace, third maxilliped, male pleon, male gonopods, and female vulvae. Potamiscus takedai sp. nov. can be differentiated from congeners mainly by the strongly bent terminal segment of the male first gonopod and a relatively shorter distal segment of the male second gonopod. [ABSTRACT FROM AUTHOR]

Telphusa austeniana Wood-Mason, 1871 is a poorly known potamid crab described from a single female specimen from Meghalaya state, northeastern India, and its position in Tiwaripotamon Bott, 1970 has been questioned. Its systematic position is now clarified based on the examination of the female holotype and a male specimen recently collected from a cave near the type locality. The species is transferred from Tiwaripotamon to a new genus, Krishnamon gen. nov. on the basis of the differences in the structures of the epigastric cristae, male pleon, male sixth pleonal somite, male telson, gonopods, and vulvae. The geographic distributions of the two genera are some 1,000 km apart. The new genus has affinities with Doimon Yeo & Ng, 2007, and Indochinamon Yeo & Ng, 2007, but can be distinguished mainly by its extremely slender and elongated ambulatory legs. While Krishnamon austenianum (Wood-Mason, 1871) comb. nov. is now recorded from limestone caves, it does not, however, possess the troglomorphic features of an obligate troglobite. [ABSTRACT FROM AUTHOR]

• Mitogenome order data are expanded to 56 species in 32 genera of freshwater crabs. • Nine gene order patterns were discovered in these freshwater crab mitogenomes. • Mitogenome gene order provides a powerful means for phylogenetics of Potamiscinae. We present here a combined mitogenome gene order dataset totalling 62% of the known genera of East Asian potamiscine freshwater crabs that includes first-time mitogenome data for 14 species and gene order data from 37 other species of potamiscines. A surprisingly high number of mitogenome gene order rearrangements were found in the taxa studied (comprising nine different rearrangements and seven major patterns, one of which has two sub-arrangements). Our phylogenetic reconstructions indicate that the mitogenome gene order rearrangements are associated with the evolutionary history of potamiscine lineages. We also used a new Event-based Maximum Parsimony method to reconstruct ancestral gene orders, which takes into consideration gene duplication, pseudogeneticization, and tandem duplication random loss. Furthermore, shared mitogenome gene order patterns were used to inform the taxonomic placement of Sinopotamon parvum , and the cryptic diversity in Potamiscus. The remarkably frequent mitogenome rearrangements in potamiscine freshwater crabs have great potential to contribute to our understanding of the evolutionary history of these highly diverse decapods in East Asia. [ABSTRACT FROM AUTHOR]