Indochinamon chuahuong, Do & Nguyen & Le, 2016

Do, Van Tu, Nguyen, Tong Cuong & Le, Hung Anh, 2016, A new species of the genus Indochinamon Yeo & Ng, 2007 (Crustacea: Brachyura: Potamoidea: Potamidae) from northern Vietnam, Raffles Bulletin of Zoology 64, pp. 187-193 : 187-191

Indochinamon chuahuong , new species

( Figs. 2–5 )

Material examined. Holotype - male (76.1 × 53.0 mm) ( IBER-FC ICx01), Huong Pagoda , Huong Son commune, My Duc district, Ha Noi province, Vietnam, 20°37’3.8”N 105°44’30.0”E, coll. local collector, 10 May 2014.

Paratypes – 2 males (71.4 × 51.1 mm, 72.1 × 51.1 mm) ( IBER-FC ICx02–03) , 1 female (59.8 × 43.3 mm) (IEBR- FC ICx04), same data as holotype .

Comparative material. Indochinamon bavi Naruse, Nguyen & Yeo, 2011: 3 males (59.9 × 57.8 mm, 50.6 × 38.9 mm, 50.0 × 38.4 mm) ( IEBR-FC IBx01–03), Ba Vi National Park, Ha Noi, Vietnam, coll. local collector, 8 November 2013; I. dangi Naruse, Nguyen & Yeo, 2011: 1 male (52.02 × 39.03 mm) ( IEBR-FC IDx01), Dien Bien province, Vietnam, coll. Pham The Cuong, 5 October 2014; I. kimboiense ( Dang, 1975) : 1 male (69.8 × 51.6 mm) ( IEBR-FC IKx01), Ngoc Son, Ngo Luong, Lac Son commune, Hoa Binh province, Vietnam, coll. Pham The Cuong, 5 October 2014; I. phongnha Naruse, Nguyen & Yeo, 2011: 7 males (80.30 × 58.9 mm, 73.1× 53.0 mm, 62.5 × 46.5 mm; 58.8 × 43.5 mm, 54.5 × 41.4 mm, 52.8 × 40.2 mm, 51.5 × 39.8 mm) ( IEBR-FC IPx01–03, Phong Nha – Ke Bang National Park, Quang Binh province, Vietnam, coll. Do Van Tu, 24 April 2014. I. tannanti ( Rathbun, 1904) : 2 males (51.2 × 38.9 mm, 47.6 × 35.2 mm) ( IEBR-FC ITx01–02, Da Bac District, Hoa Binh province, Vietnam, coll. Do Van Tu, 14 May 2015.

Diagnosis. Carapace broader than long (mean 1.4 times), anterolateral margin convex, distinctly serrated; the brachial region slightly swollen when viewed dorsally. Ambulatory legs relatively long. G1 broad, gently sinuous; terminal segment relatively short, about 0.4 times the length of the subterminal segment, about 3.3 times longer than broad, distally curved outwards, outer margin swollen at base, with very low, narrow dorsal flap.

Description. Carapace broader than long, CW ca. 1.4 times CL, low, dorsal surface glabrous; carapace regions welldefined; cervical groove shallow; epigastric cristae distinct, rugose, not sharp, separated by a distinct groove which opens up into inverted V-shape posteriorly, separated from postorbital cristae by very short, shallow groove; postorbital cristae weakly granulose, gently sloping posterolaterally before breaking up into faint granules before the epibranchial tooth; regions behind epigastric and postorbital cristae with weak rugae and granules ( Fig. 2A, B ). Frontal to orbital margins gently sinuous, frontal region weakly granular. Supra- and infraorbital margins interrupted just below external orbital angle, weakly granulated; orbital region

RAFFLES BULLETIN OF ZOOLOGY 2016

smooth; suborbital region with few granules; brachial region slightly swollen when viewed dorsally ( Fig. 2A, 2B ); subhepatic and subbranchial regions slightly rugose ( Fig. 2B, C ). External orbital angle relatively broadly triangular, outer margin serrated; epibranchial tooth small but prominent, sharp; anterolateral margin convex, distinctly serrated, distinctly cristate; posterolateral margins strongly convergent posteriorly; branchial regions granulose to slightly rugose ( Fig. 2B, C ). Posterior margin of epistome with 3 lobes, median longest, triangular, lateral lobes lined with granules ( Fig. 2C ).

Ischium of third maxilliped rectangular, about 1.6 times longer than broad, vertical sulcus well defined; merus squarish with concave outer surface, about 0.5-0.6 times the length of the ischium; exopod longer than ischium, exceeding upper edge of ischium but not reaching midpoint of merus, with well-developed flagellum, about 0.4 times the width of the merus ( Fig. 3B ).

Male cheliped carpus with rugose outer surface, inner part covered with rounded forward-directed granules, weakly rugose; not distinctly swollen; fingers as long as palm, slightly hook-shaped distally, cutting edge regularly lined with teeth, without distinct gap when closed ( Fig. 3C ).

Ambulatory legs glabrous, relatively long, slender; second pair longest, dactylus long, slender, approximately long as propodus, about 6.5 times longer than proximal width, with low, sharp ridge; merus of first, second, third and fourth pairs about 4.3, 5.9, 5.4, 5.0 times longer than wide, respectively ( Fig. 2A ).

Suture between sternites 2 and 3 complete, distinct, gently curves upward medially; suture between sternites 3 and 4 not discernible ( Fig. 3A ). Male sternoabdominal cavity reaching imaginary line joining median points of cheliped bases ( Fig. 3A ). Male abdomen narrowly triangular; telson longer than width, lateral margin very slightly concave, tip rounded, slightly longer than somite 6; somite 6 with lateral margins convex; lateral of margins of somites 4 to 5 straight; lateral margins of somite 3 gently convex ( Fig. 3A ).

G1 broad, gently sinuous ( Fig. 4A, C, E ). Terminal segment relatively short, subcylindrical, about 0.4 times the length of the subterminal segment, 3.3 times longer than broad; distally curved outwards, tapering distally, distinct ventral distal opening, swelling on outer margin at base when viewed ventrally ( Fig. 4B, D, F ); groove for G2 on dorso-lateral surface medially, dorsal flap (protuberance of ventral outer surface) very low, visible from dorsal view, about 0.3 times the length of terminal segment; subterminal segment broad, with distinct subrectangular cleft on subdistal outer margin of dorsal surface, distal part of outer margin weakly concave ( Fig. 4B, D, F ). G2 longer than G1, flagellum curving outwards, U- shaped, distal segment distinctly longer than half the length of the basal segment; outer margin of basal segment expanded ( Fig. 4G, H ).

Size. This species is quite large, with the largest recorded male specimens measuring 76.1× 53.0 mm. From what has been published, Indochinamon chuahuong is one of largest freshwater crabs known from Vietnam ( Yeo & Ng, 2007; Nasure et al., 2011; Dang & Ho, 2012).

Etymology. The new species is named after the type locality, Chua Huong. The name is used as a noun in apposition.

Live coloration. The dorsal carapace, chelipeds and walking legs are mostly dark orange ( Fig. 2A ).

Remark. This new species can be separated from congeners by a suite of characteristics, including broader carapace; distinctly serrated, convex anterolateral margin; long ambulatory legs; G1 terminal segment curved outwards, with very low dorsal flap visible only from dorsal. Nevertheless, the most important characters that distinguish the new species from the other species of the genus Indochinamon are the prominently serrated anterolateral margins and the distinctly long ambulatory legs. Only four species of Indochinamon ( I. chuahuong , I. bavi , I. kimboiense and I. phongnha ) possess a dorsal flap (protuberance of ventral outer surface) at the terminal segment of the G1. However, I. chuahuong can be distinguished from the other three species by a combination of morphological characters ( Table 1).

Carapace margin and longer legs of I. chuahuong are similar to Kanpotamon duangkhaei Ng & Naiyanetr, 1993 from northern Thailand. However, the shape of the G1 terminal segment differs in K. duangkhaei in the distinct bulbous structure on the proximal part of the G1’s outer margin. In addition, the suture between sternites 2 and 3 are gently concave in K. duangkhaei while convex in I. chuahuong .

Habitat. Indochinamon chuahuong was collected from an innominate limestone mountain in a forest near the center of Chua Huong ( Fig. 5A, B ). This new species is believed to be semi-terrestrial, as it has been collected in wet forest habitats distant from local streams.

Conservation status. Recent surveys indicate that I. chuahuong has a highly-localised distribution in the limestone forests of Chua Huong, which are not in a protected area and thus deforestation is still ongoing (unpublished data). This species could not be found in other regions of northern Vietnam during our surveys. The extent of occurrence was estimated lower than 20,000 km 2. In addition, I. chuahuong is harvested by local people to sell as food and pets to tourists ( Fig. 5C, D ). Therefore, this species should be considered at least as Vulnerable (VU) on the IUCN Red List Categories and Criteria ( IUCN, 2012) due to its highly-localised range, deforestation of its habitat, and the presumed impact of over-harvesting for tourism.

Figures

Fig. 2. Indochinamon chuahuong, new species, holotype male (76.1 × 53.0 mm) (IBER-FC IC×01), Huong Pagoda, Huong Son commune, My Duc district, Ha Noi province, Vietnam. A, overall habitus; B, dorsal view of carapace; C, frontal view of carapace.

Fig. 3. Indochinamon chuahuong, new species, holotype male (76.1 × 53.0 mm) (IBER-FC IC×01), Huong Pagoda, Huong Son commune, My Duc district, Ha Noi province, Vietnam. A, ventral view showing anterior thoracic sternum and abdomen; B, left third maxilliped; C, chela outer view.

Fig. 4. Indochinamon chuahuong, new species, holotype male (76.1 × 53.0 mm) (IBER-FC IC×01), Huong Pagoda, Huong Son commune, My Duc district, Ha Noi province, Vietnam. A, ventral view of left G1; B, ventral view of distal part of left G1; C, dorsal view of left G1; D, dorsal view of distal part of left G1; E, lateral view of left G1; F, lateral view distal part of left G1; G, dorsal view of left G2; H, left G2 of terminal segment.

Fig. 5. A, B, a habitat in Huong Pagoda, Huong Son commune, My Duc district, Ha Noi province, Vietnam; C, D, Indochinamon chuahuong, new species, in a cage being offered for sale to tourists.