Saturday, March 31, 2018

[Crustacea • 2017] Cantopotamon n. gen. • A New Genus of Freshwater Crabs (Decapoda: Brachyura: Potamidae) from Guangdong, China, with Descriptions of Four New Species


Cantopotamon zhuhaiense,  C. hengqinense & C. yangxiense 

Huang, Ahyong & Shih, 2017

 A new genus and four new species of freshwater crab, Cantopotamon zhuhaiense n. gen., n. sp., C. shangchuanense n. gen., n. sp., C. hengqinense n. gen., n. sp. and C. yangxiense n. gen., n. sp. are described from Guangdong, China, based on morphology and two mitochondrial markers (16S rDNA and cytochrome oxidase subunit I). Species of Cantopotamon closely resemble species of Yarepotamon Dai & Türkay, 1997, but differ by the combination of carapace, third maxilliped, male pleon, male first gonopod and female vulva characters. Molecular data derived from the mitochondrial 16S rDNA also supports the establishment of the new genus.

Key Words: Potamidae, Cantopotamon, New genus, New species, Freshwater crab, Morphology, 16S rDNA, Cytochrome oxidase subunit I.


Fig. 12. Colour in life.
 (A) Cantopotamon zhuhaiense n. gen., n. sp., not collected; (B) C. shangchuanense n. gen., n. sp., male paratype (21.0 × 17.2 mm) (SYSBM 001428); (C) C. hengqinense n. gen., n. sp., male holotype (19.9 × 16.0 mm) (SYSBM 001558); (D) C. yangxiense n. gen., n. sp., female paratype (18.5 × 14.9 mm) (SYSBM 001563).

Taxonomy 
Family Potamidae Ortmann, 1896 
Subfamily Potamiscinae Bott, 1970 

Genus Cantopotamon n. gen. 

Type species Cantopotamon zhuhaiense n. gen., n. sp., by present designation. 

Diagnosis: Carapace broader than long; dorsal surface slightly convex, branchial regions relatively flat (Fig. 1A); postorbital and epigastric cristae visible, confluent (Fig. 1A); external orbital angle bluntly triangular, separated from anterolateral margin by gap (Figs. 1A, B); median lobe of posterior margin of epistome triangular (Fig. 1B). Third maxilliped ischium relatively broad; exopod reaching beyond anterior margin of ischium, with flagellum (Fig. 2D). Male pleon triangular, reaching anteriorly almost to level of posterior margins of cheliped coxae (Fig. 1C). G1 slender, inner proximal section of sub-terminal segment curved dorsally, terminal segment relatively short, sinistrally twisted on left G1 (Figs. 1D, 2B, C, 9). G2 basal segment subovate (Fig. 2A). Vulva small, ovate, not reaching suture of sternites 5/ 6 (Fig. 11). 


Etymology: The genus name is a combination of Canton, synonym for Guangdong, the province in which this genus occurs, and the generic name Potamon. Gender: neuter.

 Remarks: Although superficially similar to some species of Yarepotamon, Cantopotamon n. gen. can easily be distinguished by its confluent postorbital cristae and epigastric cristae (Fig. 1A) (versus separate in Yarepotamon, cf. Dai & Türkay, 1997: pl. II, fig. 2), twisted terminal segment of the G1 (Fig. 2C) (versus not twisted in Yarepotamon, cf. Dai & Türkay, 1997: fig. 6, 4) and relatively small female vulvae that do not reach the suture of sternites 5/6 (Fig. 11A) (versus female vulvae reaching suture of sternites 5/6 in Yarepotamon, cf. Dai & Türkay, 1997: fig. 6, 7). Yarepotamon is currently being revised by the first author. ....


Cantopotamon zhuhaiense n. sp.
Etymology: This species is named after the type locality, Zhuhai City, Guangdong Province, China.

Ecology: This species is mainly aquatic, living under rocks in small hillstreams. At its type locality, C. zhuhaiense is sympatric with Nanhaipotamon cf. guangdongense Dai, 1997 and Nanhaipotamon zhuhaiense Huang, Huang & Ng, 2012. One individual, still moving, was observed within the grasp of a Nanhaipotamon cf. guangdongense in the latter’s mud burrow, suggesting they are at least occasional prey items of Nanhaipotamon.


Cantopotamon shangchuanense n. sp. 
Etymology: This species is named after the type locality, Shangchuan Island, Taishan City, Guangdong Province, China.

Ecology: This species is mainly aquatic, living under rocks in small hillstreams. The hillstream in which it was found drains directly to the sea, with Eriocheir sp. also inhabiting the lower reaches. The species of Eriocheir was not confirmed, but given the location, it was probably E. hepuensis (see Naser et al. 2012). No other potamids where found at the type locality.


Cantopotamon hengqinense n. sp.
   Etymology: This species is named after the type locality, Hengqin Island (also known as Ilha de Montanha in Portuguese), Zhuhai City, Guangdong Province, China.

Ecology: This species is mainly aquatic, living under rocks in small hillstreams.


Cantopotamon yangxiense n. sp.
Etymology: This species is named after the type locality Yangxi, Yangjiang, Guangdong Province.

Ecology: This species is mainly aquatic, living under rocks in small hillstreams.


Chao Huang, Shane T. Ahyong and Hsi-Te Shih. 2017. Cantopotamon, A New Genus of Freshwater Crabs from Guangdong, China, with Descriptions of Four New Species (Crustacea: Decapoda: Brachyura: Potamidae). Zoological Studies. 56; 41. DOI: 10.6620/ZS.2017.56-41

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