Himalayapotamon garhwalense n. sp.

(Figs. 2–4)

Type material. INDIA: adult male, holotype (cw 43.44 mm, cl 32.04 mm, ch 18.34 mm, fw 12.70 mm), stream near Khanda, ca. 3 km south of Srinagar, Pauri Garhwal district, Uttarakhand (30.196° N and 78.777° E), altitude 718 m, 11 June 2014, coll. S. Singh (ZSI, WRC-C.1178); paratypes, 2 males (cw 38.64–40.94 mm, cl 28.08–29.70 mm, ch 16.02–17.18 mm, fw 11.78–12.72 mm), 2 females (cw 41.22–42.88 mm, cl 30.26–31.58 mm, ch 18.24– 18.96 mm, fw 12.34–12.44 mm), stream near Khanda, ca. 3 km south of Srinagar, Pauri Garhwal district, Uttarakhand (30.197° N and 78.776° E), altitude 714 m, 19 May 2014, coll. S. Singh (ZSI, WRC-C.1519).

Diagnosis. Carapace broader than long, flat; dorsal surface setose; epigastric cristae separated from postorbital cristae by distinct groove; postorbital cristae distinctly curved (Fig. 2 A). Male abdomen with sixth somite broader than long, median length nearly half greatest width; telson with concave lateral margins, apex rounded (Fig. 2 C). G1 terminal joint conical, stout, short, ca. 0.2 times combined length of subterminal joint and flexible zone, distal portion tapering gradually (Fig. 3 A, B).

Description of male holotype. Carapace broader than long (cw/cl = 1.4), flat; dorsal surface setose, unarmed except for short ridges on branchial regions, numerous granules on epigastric cristae, postorbital cristae, frontal, postfrontal regions; suborbital, sub-branchial, pterygostomial regions with rows of small granules and/or low transverse ridges; anterolateral surface of carapace slightly inflated in frontal view; anterolateral margin convex, serrated; posterolateral margin slightly converging, with short, oblique, striate; front broad, 0.3 times cw; frontal margin serrated, sinuous, distinctly bilobed, directed downwards; epigastric cristae well developed, separated from postorbital cristae by distinct groove; postorbital cristae well developed, distinctly curved, reaches epibranchial tooth; external orbital angle prominent, slightly acute, outer margin ca. 1.5 times length of inner margin, with small denticles; epibranchial tooth distinct, blunt; supraorbital, infraorbital margins serrated; postorbital region slightly concave; branchial region nearly flat; cervical grooves deep, sinuous; mesogastric groove deep, long; central gastric groove deep; second central groove behind first gastric groove deep; frontal median triangle incomplete, only dorsal margin developed, lateral margins undiscernible; epistome anteriorly unarmed, posteriorly with prominent median tooth (Fig. 2 A–C). Eyes with large corneas (Fig. 2 B).

Mandibular palp with 3 segments; terminal segment simple, undivided. First, second maxillipeds each with long flagellum on exopod. Third maxillipeds almost cover buccal cavity when closed; ischium subrectangular, longer than broad, with deep median sulcus; merus subquadrate, as long as broad; exopod longer than ischium, reaching lower third of merus, with long flagellum (Fig. 2 B, C).

Chelipeds unequal, right chela slightly large; fingers slender, as long as palm, cutting edges with distinct serrations, rows of conical teeth; dactylus proximally with 4 distinct median granules; fixed finger slightly deflexed; palm, carpus, merus with strongly rugose outer surfaces; carpus with long, acute inner distal major tooth, small supplementary tooth near base of inner distal major tooth; merus with row of granules on mesioventral margin (Fig. 2 A, B).

Ambulatory legs (p2–p5) unarmed, with very fine, small tuft of brownish bristles mostly on margins; p3 longest; carpus (p2–p5) dorsally with elevated median ridges; propodus (p2–p5) with row of small spines on posterior margin; dactylus (p2–p5) slightly curved, longer than propodus, with 4 rows of acute, distally directed spines (Fig. 2 A–C).

Thoracic sternites smooth, nearly glabrous. Suture between thoracic sternites s2/s3 distinct as deep, narrow groove, reaching lateral margins, suture between s3/s4 not visible, except for 2 short lateral grooves (Fig. 2 C).

Abdomen smooth, nearly glabrous, triangular; first somite short, second to sixth somites progressively longer; sixth somite broader than long, median length nearly half of greatest width, with slightly convex lateral margins; telson much broader than long, slightly longer than sixth somite, with concave lateral margins, apex rounded; sternoabdominal cavity deep, long, extending up to imaginary line joining median part of cheliped coxae (Fig. 2 C).

G1 sinuous; terminal joint conical, stout, short, ca. 0.2 times combined length of subterminal joint and flexible zone, distal portion tapering gradually; flexible zone almost symmetrical; subterminal joint elongated, sinuous, stouter than terminal joint (Fig. 3 A–C). G2 longer than G1, with short flexible zone, followed by curved, hook-like, long terminal tube, ca. 0.4 times length of terminal segment (Fig. 3 D).

Live colour. Carapace dorsal surface light olive green, and chelipeds and ambulatory legs orange-yellow.

Paratypes. The male paratypes (ZSI, WRC-C.1519) are similar to the holotype in overall physiognomy and gonopod structure. The postorbital cristae are nevertheless distinctly separated from the epibranchial tooth in the paratype males.

The female paratypes (ZSI, WRC-C.1519) resemble the holotype in non-sexual characters. The abdomen of females is very broad, narrowly ovate, and almost conceals the sternum except for the thoracic sternite 2 in the bigger female and anterior thoracic sternites in the smaller female (Fig. 4 A, B). Their vulvae are ovate, very large, occupying more than half-length of the thoracic sternite 6, situated adjacent to the margin with the thoracic sternite 5 and almost invisible in ventral view due to the presence of a highly protruding sternal cover (Fig. 4 C, D).

Etymology. The specific epithet refers to Garhwal, an administrative division of the Indian state of Uttarakhand, where the crab seems to be endemic.

Type Locality. Khanda near Srinagar, Pauri Garhwal district, Uttarakhand, India (30.196° N and 78.777° E) (altitude 718 m).

Remarks. Himalayapotamon garhwalense n. sp. differs from all congeners by the following suite of carapace and gonopod characters: epigastric cristae separated from postorbital cristae by distinct groove; postorbital cristae distinctly curved; sixth male abdominal somite relatively long, median length nearly half greatest width; male telson with concave lateral margins, apex rounded; G1 terminal joint conical, stout, short, ca. 0.2 times combined length of subterminal joint and flexible zone, distal portion tapering gradually (Figs. 2 A,C, 3A, B).

As in H. garhwalense n. sp., the epigastric cristae are separated from the postorbital cristae by a distinct groove in the remaining species of Himalayapotamon (Fig. 2 A for H. garhwalense, Fig. 5A for H. monticola; see Rathbun 1904: pl. 10, fig. 1 for H. koolooense; Alcock 1910: pl. 1, fig. 2 for H. emphyseteum, fig. 3 for H. bifarium, pl. 10, fig. 39 for H. atkinsonianum; Bouvier 1918: fig. 9 for H. babaulti; Pretzmann, 1963: pl. 1, fig. 1 for H. marinellii; Pretzmann 1966: pl. 3, fig. 10 for H. kasaulis; Brandis & Sharma 2005: fig. 5A for H. sunkoshiense) except for H. ambivium, in which, the groove between the epigastric and postorbital cristae is indistinct (Fig. 5B). Among the species of Himalayapotamon, only H. bifarium and H. monticola have a relatively short sixth male abdominal somite (Fig. 5C for H. monticola; see Alcock 1910: pl. 1, fig. 3a for H. bifarium). Other species of the genus, including the new species have a relatively long sixth male abdominal somite (Fig. 2 C for H. garhwalense, Fig. 5 D for H. ambivium; see Rathbun 1904: text fig. 10b for H. koolooense; Alcock 1910: pl. 1, fig. 2a for H. emphyseteum; Pretzmann, 1963: pl. 1, fig. 4 for H. marinellii; Pretzmann 1966: pl. 3, fig. 11 for H. kasaulis; Bott 1970: pl. 44, fig. 13 for H. atkinsonianum). The acute apex of the telson of H. bifarium and H. kasaulis differentiates them from all congeners (see Alcock 1910: pl. 1, fig. 3a for H. bifarium; Pretzmann 1966: pl. 3, fig. 11 for H. kasaulis). All the species of Himalayapotamon, including the new species, can be distinguished by the conical G1 terminal joint (Fig. 3 A, B for H. garhwalense; Fig. 5 E for H. bifarium; see Bouvier 1918: fig. 10I for H. babaulti; Pretzmann, 1963: pl. 3, fig. 11 for H. marinellii; Pretzmann 1966: pl. 3, fig. 9 for H. kasaulis; Bott 1970: pl. 38, fig. 19 for H. koolooense; Brandis 2001: fig. 4c for H. emphyseteum; Brandis & Sharma 2005: fig. 5C for H. sunkoshiense) as compared to the sinuous or S-shaped G1 terminal joint of H. atkinsonianum and H. monticola (Fig. 5 F for H. monticola; see Brandis 2001: fig. 3c for H. atkinsonianum). The stout G1 terminal joint of H. garhwalense n. sp., H. babaulti and H. marinellii (Fig. 3 A, B for H. garhwalense; see Bouvier 1918: fig. 10I for H. babaulti; Pretzmann, 1963: pl. 3, fig. 11 for H. marinellii) separates them from H. emphyseteum, H. koolooense and H. sunkoshiense with a slender G1 terminal joint (see Bott 1970: pl. 38, fig. 19 for H. koolooense; Brandis 2001: fig. 4c for H. emphyseteum; Brandis & Sharma 2005: fig. 5C for H. sunkoshiense).

Owing to the stout and conical appearance of the G1 terminal joint, H. garhwalense n. sp. is most similar to H. babaulti and H. marinellii. Both H. garhwalense n. sp. and H. marinellii can nevertheless distinguished from H. babaulti by their gradually more narrow distal portion of the G1 terminal joint (Fig. 3 B for H. garhwalense; see Pretzmann 1963: pl. 3, fig. 11 for H. marinellii) (vs. suddenly tapered distal portion of the G1 terminal joint in H. babaulti; see Bouvier 1918: fig. 10I).

The new species is easily differentiated form H. marinellii by its proportionately shorter G1 terminal joint, about 0.2 times the combined length of the subterminal joint and flexible zone (Fig. 3 A) (vs. long G1 terminal joint, about 0.3 times the combined length of the subterminal joint and flexible zone in H. marinellii; see Pretzmann 1963: pl. 3, fig. 11) in addition to having a distinctly curved postorbital cristae (Fig. 2 A) (vs. almost straight postorbital cristae in H. marinellii; see Pretzmann 1963: pl. 1, fig. 1) and a male telson that has concave lateral margins (Fig. 2 C) (vs. male telson with straight lateral margins in H. marinellii; see Pretzmann 1963: pl. 1, fig. 4).

Ecological notes. Crabs were collected under stones and small boulders of a stream (<50 cm deep) (Fig. 6) during summer (May and June). The water temperature of the stream was ranged from 14°C to 28°C (S. Singh, unpublished data).

Geographical distribution. Himalayapotamon garhwalense n. sp. is known only from the type locality, Khanda near Srinagar of Pauri Garhwal district of Uttarakhand. The species seems to be distributed in other localities of the Garhwal division.