Monday, January 7, 2019

[Crustacea • 2018] The Freshwater Crabs (Decapoda, Potamidae) of Macau, with the Description of Nanhaipotamon macau and the Redescription of Nanhaipotamon wupingense

Nanhaipotamon macau 
Huang, Wong & Ahyong, 2018

Four species of freshwater crabs from three genera and two families (Cantopotamon hengqinense Huang, Ahyong & Shih, 2017, Nanhaipotamon guangdongense Dai, 1997, Nanhaipotamon macau sp. n., and Somanniathelphusa zanklon Ng & Dudgeon, 1992) are documented from Macau for the first time. One new species, Nanhaipotamon macau sp. n., is described. The large flap on the male first gonopod terminal segment sets it apart from all other known congeners except N. wupingense Cheng, Yang, Zhong & Li, 2003, from Fujian. Characters of the carapace, male first gonopod and size, however, clearly differentiate these two species. Preliminary genetic studies also suggest that the two are not closely related. A neotype is designated for N. wupingense. The taxonomic status of Nanhaipotamon guangdongense is also discussed. Notes on the general biology and conservation status of these crabs are also included.

Keywords: Freshwater crabs, Gecarcinucidae, Macau, new species, Potamidae, systematics

Figure 2. The freshwater crabs of Macau, colour in life.
 Nanhaipotamon macau sp. n., male (29.0 × 24.2 mm), SYSBM 001654 (A);
Nanhaipotamon guangdongense Dai, 1997, male (35.9 × 28.8 mm), SYSBM 001645 (B);
Cantopotamon hengqinense Huang, Ahyong & Shih, 2017, male, specimen not collected (C);
Somanniathelphusa zanklon Ng & Dudgeon, 1992, photographed in Zhuhai, specimen not collected (D).

•  Family Potamidae Ortmann, 1896
Subfamily Potamiscinae Bott, 1970

Genus Cantopotamon Huang, Ahyong & Shih, 2017

••  Cantopotamon hengqinense Huang, Ahyong & Shih, 2017

Distribution: Hengqin Island, Zhuhai, Guangdong; Coloane, Macau.

 Nanhaipotamon macau sp. n., male (29.0 × 24.2 mm), SYSBM 001654 

Genus Nanhaipotamon Bott, 1968

•• Nanhaipotamon macau sp. n.

Diagnosis: Carapace broader than long, regions indistinct, dorsal surface convex, anterolateral region weakly rugose (Figs 3A, 4B); postorbital cristae sharp, laterally expanded, almost fused with epibranchial teeth and epigastric cristae (Figs 3A, 4B); external orbital angle sharply triangular, outer margin gently convex to almost straight, separated from anterolateral margin by conspicuous gap (Figs 3A, B, 4B); sub-orbital regions covered by sparse low granules, pterygostomial regions covered with short rows of a few rounded granules; sub-hepatic regions covered with lined striae (Fig. 3B); maxilliped III exopod reaching to proximal one-third of merus with short flagellum (Fig. 5A); female vulva ovate, medium-sized, positioned closely to one another (Fig. 4D); male pleon triangular, lateral margins almost straight (Fig. 3C); G1 slender, subterminal segment tapering distally, terminal segment large, distally expanded, distal margin laminar, apex blunt, directed outward (Figs 5C–E, 6A–C). G2 basal segment subovate (Fig. 5B).

Etymology: This species is named after the type locality, Macau; used as a noun in apposition.

Habitat: Nanhaipotamon macau sp. n. is a typical semi-terrestrial species that burrows in wet soil in the bank adjacent to hill streams. It was sympatric with Cantopotamon hengqinense at three localities. 

Distribution: Coloane, Macau.

••  Nanhaipotamon guangdongense Dai, 1997

 •• Nanhaipotamon wupingense Cheng, Yang, Zhong & Li, 2003

• Family Gecarcinucidae Rathbun, 1904
Genus Somanniathelphusa Bott, 1968

 •• Somanniathelphusa zanklon Ng & Dudgeon, 1992

 Chao Huang, Kai Chin Wong and Shane T. Ahyong. 2018. The Freshwater Crabs of Macau, with the Description of A New Species of Nanhaipotamon Bott, 1968 and the Redescription of Nanhaipotamon wupingense Cheng, Yang, Zhong & Li, 2003 (Crustacea, Decapoda, Potamidae). ZooKeys. 810: 91-111.  DOI: 10.3897/zookeys.810.30726

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