Himalayapotamon chambaensis,

Valarmathi, Kandasamy, 2017, Himalayapotamon chambaensis, a new species of freshwater crab (Crustacea: Brachyura: Potamidae) from Himachal Pradesh, India, Zootaxa 4324 (3), pp. 482-490: 483-488

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Himalayapotamon chambaensis

n. sp.

Himalayapotamon chambaensis  n. sp.

( Figs. 2–4View FIGURE 2View FIGURE 3View FIGURE 4)

Type material. INDIA: adult male, Holotype (cw 53.13 mm, cl 42.74 mm, ch 22.64 mm, fw 14.79 mm), Rajira, 19 km from Chamba town, Chamba district , Himachal Pradesh (32° 30.507’ N 76°10.358’ E), 11 September 2014, coll. K. Valarmathi (ZSI C6498/2)GoogleMaps  . Paratypes, 5 adult males (Largest cw 52.60 mm, cl 42.80 mm, fw 14.95 mm, ch 23.72 mm; smallest cw 31.18 mm, cl 25.01 mm, ch 13.30 mm, fw 9.32 mm), Rumali, 19 km from Chamba town , Chamba district , Himachal Pradesh (32°34.118’ N 76°06.099’ E), altitude 1020 mt, 10 September 2014, coll. K. Valarmathi (ZSI C 6505/2)GoogleMaps  ; 1 adult female (cw 34.95 mm, cl 28.18 mm, ch 15.43 mm, fw 10.92 mm), Singara, 16 km from Chamba town, Chamba district , Himachal Pradesh (32°35.866’ N 76°12.698’E), altitude 1170 mt, 8 September 2014, coll. K. Valarmathi (ZSI C 6504/2). Other materialGoogleMaps  : 2 males (largest cw 49.61 mm, cl 39.92 mm, ch 21.16 mm, fw 12.64 mm; smallest cw 19.69 mm, cl 8.27 mm, ch 15.54 mm, fw 5.78 mm), Binayag, 15 km from Chamba town, Chamba district , Himachal Pradesh (32°34.129’ N 76°08.016’ E), altitude 876 mt, 10 September 2014, coll. K. Valarmathi (ZSI C6499/2)GoogleMaps  ; 2 males (largest cw 41.23 mm, cl 33.26 mm, ch 17.24 mm, fl 11.47 mm, smallest cw 22.18 mm, cl 17.50 mm, ch 9.45 mm, fw 6.83 mm), 3 females (largest cw 37.40 mm, cl 30.46 mm, ch 16.25 mm, fw 11.31 mm; smallest cw 19.92 mm, cl 15.48 mm, ch 8.07 mm, fw 5.48 mm), Ohli, about 16 km from Chamba town, Chamba district , Himachal Pradesh (32°32.149’ N 76°06.974’ E), altitude 1064 mt, 10 September 2014, coll. K. Valarmathi (ZSI C 6500/2)GoogleMaps  ; 1 male (cw 47.93 mm, cl 38.92 mm, ch 20.25 mm, fw 12.97 mm) 1 female (cw 25.82 mm, cl 20.20 mm, ch 10.57 mm, fw 8.38 mm) Pandanala, 12 km from Chamba town, Chamba district , Himachal Pradesh (32°35.191’ N 76°12735’ E), 8 September 2014, coll. K. Valarmathi (ZSI C 6501/2)  ; 1 male (cw 51.01 mm, cl 40.21 mm, ch 21.95 mm, fw 12.98 mm), 1 female (cw 25.42 mm, cl 19.36 mm, ch 10.81 mm, fw 7.72 mm), Rock Garden, Devidhera, 32 km from Chamba town, on Pathankot-Chamba road, Chamba district , Himachal Pradesh (32°33.981’N 75°59.489’E), altitude 1232 mt, 9 September 2014, coll. K. Valarmathi (ZSI C 6502/2)GoogleMaps  ; 2 males (largest cw 25.10 mm, cl 19.86 mm, ch 10.79 mm, fw 7.83 mm; smallest cw 24.74 mm, cl 19.42 mm, ch 9.68 mm, fw 7.57 mm) 2 females (largest cw 18.67 mm, cl 14.96 mm, ch 7.84 mm, fw 6.47 mm.; smallest cw 16.72 mm, cl 13.30, ch 7.76 mm, fw 5.22 mm.), Drah village near Bhala, Chamba district , Himachal Pradesh (32°34.965’ N 78°13.034’ E), altitude 1623 mt, 8 September 2014, coll. K. Valarmathi (ZSI C 6503/2).GoogleMaps 

Diagnosis. Carapace broader than long; dorsal surface smooth, flat, frontal region with median longitudinal granular ridge which extends from behind frontal margin to epigastric cristae ( Figs. 2A, BView FIGURE 2); anterolateral region with transverse, oblique granules; external orbital angle acute; cervical groove S-shaped, anterior part prominent while posterior part inconspicuous; G1 terminal segment relatively large, bent outwardly; in mature adult G1 terminal segment visible in ventral view even when pleon closed ( Figs. 3B, DView FIGURE 3; 5F); G2 distal segment long, coiled, terminal part bent towards base ( Figs. 3BView FIGURE 3; 4E, F).

Description of male holotype. Carapace broader than long, cw 1.24 times than cl. Dorsal surface smooth, almost flat, slightly convex longitudinally ( Figs. 2A, BView FIGURE 2); regions well defined; epigastric cristae distinctly rugose, oblique, clearly separated from post orbital cristae, which is lower than epigastric cristae, almost straight, post orbital cristae distinctly cut by cervical groove at a point just below inner margin of external orbital angle, well before anterolateral margin, forming small crest with remaining part of post orbital cristae; anterolateral region with transverse, oblique granules on upper part, oblique striae on posterior half; posterolateral region almost smooth, with some faint oblique striae ( Fig. 2AView FIGURE 2); mesogastric region slightly convex, mesogastric groove Yshaped, long, frontal part extending between epigastric cristae; urogastric region ovate; cervical groove S-shaped, anterior part deep, posterior part inconspicuous; cardiac region slightly convex, cardiac groove prominent in posterior part only, semi-circular in shape ( Fig. 2AView FIGURE 2). Frontal margin sinuous, slightly concave medially, post frontal region broad, with obliquely transverse granules, a small almost straight median longitudinal ridge formed by a series of small granules from frontal margin to groove between epigastric cristae, frontal and orbital margins lined with granules; infra orbital margin with fine serrations, interrupted just below external orbital angle; surface of sub orbital regions rough, with short granules, external orbital angle acutely pointed, sharp, straight; outer margin slightly inflated and lined with small granules; inner margin smooth; anterolateral margin gently convex, granular; posterolateral margin almost smooth only some horizontal striation along posterolateral borders of carapace; posterolateral margin oblique, convergent posteriorly ( Fig. 2AView FIGURE 2). Posterior margin of epistome with inconspicuously 3 lobes, median tooth triangular, lower angle blunt, lateral 2 lobes sharply inflated in frontal view ( Fig. 2BView FIGURE 2). Ischium of third maxilliped broadly rectangular, with median longitudinal groove, merus of external maxilliped slightly broader than long, concave medially, exopod with flagellum longer than half width of merus ( Fig. 2BView FIGURE 2, 4AView FIGURE 4).

Upper surfaces of chelipeds rugose, covered with obliquely pointed granules; inner angle of carpus with short submedian tooth, sharp, followed by 2 small teeth basally; fingers as long as palm, cutting edge lined with teeth, without large gap when closed ( Fig. 2AView FIGURE 2); one cheliped slightly larger than other ( Fig. 2AView FIGURE 2). Ambulatory legs not much longer than chelipeds; dactylus slender, long, longer than propodus, tips of the fingers crosses when closed; propodus of third leg 2.66–2.75 times longer than width ( Fig. 2AView FIGURE 2).

Sternopleonal cavity reaching to imaginary line across upper part of coxae of chelipeds ( Fig. 2CView FIGURE 2; 3B). Male pleon tongue-shaped; third somite visible ventrally, widest, sixth somite trapezoidal, lower border of sixth somite broader than upper border, lateral borders converging, telson distinctly broader than long ( Fig. 2CView FIGURE 2). G-1 very stout, distal end of sub terminal segment slightly bent outwards, sub terminal segment 9.51 mm long, terminal segment 4.01 mm long, distinctly bent outwards, tip may extend beyond sternopleonal cavity, terminal segment with 2 rows of long, stiff setae ( Figs. 3A –C, FView FIGURE 3; 4B –D). G-2 very long, slender, basal segment cylindrical, distal segment flagelliform, as long as basal segment, prominently coiled, tip with small flap ( Figs. 3D, EView FIGURE 3; 4E, F).

Live colour. Carapace dorsal surface olive green in mature specimens; larger and presumably older specimens more brownish; front grey or slaty grey, sometimes violet; chelipeds yellowish-brown in frontal view, pale coloured ventrally. ambulatory legs brownish ( Figs. 1C, DView FIGURE 1).

Type Locality. Rajira village in Chamba District of Himachal Pradesh ( Fig. 1A, BView FIGURE 1).

Paratypes. All male paratypes have carapace and gonopod structures that are similar to those of the holotype male. The smaller (cw:cl 1.25) and medium-sized (cw:cl 1.24) specimens possess similar carapace ratios (cw:cl, 1.23) as in adult paratypes and holotype (cw:cl, 1.24). All males possess a distinct, granular anterolateral border, shorter than posterolateral border, with the posterolateral border convergent posteriorly, the anterolateral border is gently convex medially, gently convergent or almost parallel posteriorly, the epigastric cristae rugose, post orbital cristae sharp, frontal region wide, granular, mesogastric groove very deep in between epigastric ridges, frontal region separated by a distinct ridge originated from mesogastric groove, carpal spine bases flattened dorsoventrally ( Figs. 5D,EView FIGURE 5); sternopleonal cavity narrow, deeply graven, telson broader than long, widely triangular ( Fig. 5FView FIGURE 5); G1 terminal part bent outwardly according to maturities of specimens, in some mature adult it become almost 90 degree bent, in a medium male (cw 40.30 mm, cl 32.36 mm, fw 10.84, ch 17.35 mm) terminal part of G1 is visible from the outside ventral view; Paratype female (ZSI C6504/2) with almost same carapace characters as male (cw:cl, 1.24) ( Figs. 5A,BView FIGURE 5); with the pleon U-shaped ( Fig. 5CView FIGURE 5), and covering almost the entire thoracic sternum; female vulva on sternite 6, opening oblique, facing midline of sternopleonal cavity ( Fig. 5GView FIGURE 5), right cheliped slightly larger than left ( Fig. 5AView FIGURE 5).

Habitat and distribution. The new species was collected from several small streams and water seepages along the hill slopes on the roadside ( Fig. 1AView FIGURE 1). Individuals made their nest hole in the wet soil just below rocks and in daytime they hide inside the hole openings ( Fig. 1AView FIGURE 1). Crabs live below boulders in the stream. The new species has so far been collected from various locations in Chamba District, Himachal Pradesh ( Fig. 1BView FIGURE 1).

Etymology. The new species is named after the type locality, Chamba of Himachal Pradesh. The name is used as noun in apposition.

Remarks. Himalayapotamon chambaensis  n. sp. can be easily differentiated from all congeners in features like possessing a median longitudinal granular ridge behind the front to epigastric region, a distinct outwardly bent and long G-1 terminal segment and a relatively longer and circularly coiled distal segment of G-2. The new species superficially resembles H. emphyseteum (Alcock, 1909)  in having about a carapace that is distinctly wider than long, and the anterolateral part of the carapace is rugose. It clearly differs from H. emphyseteum  in the following characters: carapace convexity very low ( Fig. 2AView FIGURE 2, 5A, DView FIGURE 5), (very strong convexity of carapace due to more convex curve in frontal carapace in respect of a short and convergent posterior border of carapace in H. emphyseteum  ; see Alcock 1910: fig. 2; Brandis & Sharma 2005: fig. 4A); the telson is distinctly broader than long ( Fig. 2CView FIGURE 2, 5FView FIGURE 5) (longer than broad in H. emphyseteum  ; see Alcock 1910: fig. 2b); and the G1 terminal segment is relatively longer and bent outwards ( Fig. 3A, B, C, FView FIGURE 3; 4B –D) (G1 terminal segment short, straight in H. emphyseteum  ; see Bott 1970: fig. 17, pl. 37; Brandis & Sharma,2005: fig. 4B, C).

This new species also superficially resembles H. atkinsonianum ( Wood-Mason, 1871)  in the large and almost flat carapace, cervical groove almost clear, epigastric crest and postorbital crest though separated from each other, forms a common curve or convexity, but this new species is distinguished by several characters from the preceding ones i.e. cervical groove not so prominent in posterior part ( Fig. 2AView FIGURE 2, 5A, DView FIGURE 5) (cervical groove deep cut its all along in H. atkinsonianum  ; see Alcock 1910: fig. 39; Brandis 2001: fig. 3A; Brandis & Sharma 2005: fig. 3A); G1 terminal joint elongated more or less conical ( Fig. 3FView FIGURE 3, 4CView FIGURE 4) (G1 terminal joint S-shaped, tip dorsally elongated which crosses over the ventral part, spoon-like in H. atkisonianum  ; see Bott 1970: figs. 14, 15, pl 37; Brandis & Sharma 2005:fig. 3B, C); and the flexible zone of the G1 is elongated and symmetrically V-shaped ( Fig. 3AView FIGURE 3, 4 B – DView FIGURE 4) (flexible zone of G1 is asymmetrical; see Brandis 2001: fig. 3 B, C).

This new species is more closely related to H. marinelli ( Pretzman, 1963)  in both the carapace and gonopod structure, both the species have broad, flat moderately sculptured carapace, G1 terminal part looks alike, long and strongly angled outwardly; but the new species is distinguished by several characters from H. marinelli  ; in H. chambaensis  n. sp. the carapace is broad and only the anterolateral and frontal region is finely granular ( Fig. 2A, BView FIGURE 2; 5E) (all edges and strips significantly granular in H. marinelli  ; Pretzmann 1963: fig. 2, pl.1); external orbital angle acutely triangle, outer margin nearly straight ( Fig. 2AView FIGURE 2) (external orbital angle broad, outer margin concave in H. marinelli  ; Pretzmann 1963: fig. 1.pl.1); external orbital tooth sharp ( Fig. 2AView FIGURE 2) (external tooth dull in H. marinelli  ; Pretzmann 1963: fig.1, pl.1); the G1 terminal segment almost sub cylindrical with the tip not pointed ( Fig. 3A, C, FView FIGURE 3; 4 B –D) (G1 terminal segment conical, tip pointed in H. marinelli  ; Pretzmann 1963: fig.2, pl.1); the G1 subterminal segment is almost 2.6 times longer than the terminal segment ( Fig. 3AView FIGURE 3,CF; 4.B –D) (G1 subterminal segment 4 times longer than terminal part in H. marinelli  ; Pretzmann 1963: fig.2, pl.1); and the G2 terminal part is very long, rolled back as a full coil ( Fig. 3D, EView FIGURE 3; 4E, F) (G2 terminal segment rolled back semi circularly in H. marinelli  ; Pretzmann 1963: fig. 2).

The proposed new species superficially resembles H. sunkoshiense ( Brandis & Sharma, 2005)  , but differs from it in the G1 and G2 characters. The later species has a G1 with a straight terminal segment and the G2 is a long straight terminal tube (see Brandis & Sharma 2005: fig. 5B, C) (distinct outwardly bent long terminal segment of G1 and G2 terminal segment rolled back circularly in H. chambaensis  n. sp.).

The new species shows some similarities in the carapace characters with H. garhwalense Pati & Singh, 2017  , such as carapace being broader than long; epigastric cristae separated by post orbital cristae by a distinct groove, sixth abdominal somite broader than long. It differs from H. garhwalense  by several other carapace and gonopod characters. The post orbital cristae slightly concave in H. chambaensis  n. sp. ( Fig. 2A, BView FIGURE 2) (post orbital cristae distinctly curved in H. garhwalense  ; Pati & Singh 2017: fig. 2A, B); the G1 terminal segment is relatively long, sub cylindrical, ca. 0.4 times of combined length of sub-terminal joint and flexible zone ( Fig. 3A, C, FView FIGURE 3; 4.B –D) (G1 terminal segment is short, stout and conical, ca. 0.2 times of combined length of sub terminal joint and flexible zone in H. garhwalense  ; Pati & Singh 2017: fig. 3A –C); G2 terminal part is very long, rolled back as full coil ( Fig. 3D, EView FIGURE 3; 4.E,F) (G2 terminal tube relatively short, curved, hook like in H. garhwalense  ; Pati & Singh 2017: fig. 3D).