Teretamon kempi, Mitra & Payra & Chandra, 2018

Mitra, Santanu, Payra, Arajush & Chandra, Kailash, 2018, A new species of freshwater crab of the genus Teretamon Yeo & Ng, 2007 (Decapoda: Brachyura: Potamidae) from Arunachal Pradesh, northeastern India, Zootaxa 4500 (4), pp. 587-595 : 588-594

publication ID	https://doi.org/ 10.11646/zootaxa.4500.4.8
publication LSID	lsid:zoobank.org:pub:F61A839A-0967-46BA-92B6-F183FA4B87D1
persistent identifier	https://treatment.plazi.org/id/5D0ADF70-8013-8D0F-46A0-FF7771A473BD
treatment provided by	Felipe
scientific name	Teretamon kempi
status	sp. nov.

Treatment

Teretamon kempi View in CoL n. sp.

( Figs. 2–5 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 )

Potamon (Geothelphusa) adiatretum, Kemp 1913: 298 View in CoL , 299, pl. 18 figs. 10–12. [not P. (G.) adiatretum Alcock, 1909 View in CoL ] Tiwaripotamon adiatretum, Bott 1970: 153 , pl.38. fig. 20; pl. 45 fig. 18 (in part). [not P. (G.) adiatretum Alcock, 1909 ]

Material examined. All material are from the Namdapha Tiger Reserve in Changlang District, Arunachal Pradesh, India ( Fig. 1 View FIGURE 1 ).

Holotype, male (cw 18.5 mm, cl 14.3 mm, ch 8.8 mm, fw 5.8 mm), hill stream near Hornbill camp (27.54°N and 96.44°E), altitude 657 m, 10March 2017, coll. J. Saini et al. (ZSI-C7128/2).

Paratypes: 1 male (cw 17.2 mm, cl 13.7 mm, ch 7.8 mm, fw 5.3 mm), Deban (27.48°N, 96.40°E), altitude 345 m, 24 June 2017, coll. J. Saini et al. (ZSI-C7129/2) GoogleMaps ; 1 female (cw 13.4 mm, cl 10.1 mm, ch 6.1 mm, fw 4.7 mm), 19 mile (27.48°N, 96.40°E), altitude 466 m, 27 June 2017, coll. J. Saini et al. (ZSI-C7130/2); 1 male (cw 14.6 mm, cl 10.8 mm, ch 6.5 mm, fw 4.9 mm), Deban (27.48°N, 96.40°E), altitude 345 m, 3 March 2017, coll. J. Saini et al. (ZSI-C7131/2) GoogleMaps ; 3 males (cw 10.1–17.6 mm, cl 7.7–14 mm, ch 4.6–8.3 mm, fw 3.7–5.5 mm), Lankhai nala (27.50°N, 96.39°E), altitude 375 m, 6 March 2017, coll. J. Saini et al. (ZSI-C7132/2) GoogleMaps ; 1 male (cw 14.9 mm, cl 12 mm, ch 7.1 mm, fw 5.3 mm), Deban (27.48°N, 96.40°E), altitude 345 m, 27 June 2017, coll. J. Saini et al. (ZSI- C7133/2) GoogleMaps ; 1 male (cw 15.5 mm, cl 12.2 mm, ch 7.3 mm, fw 5.1 mm), Deban (27.48°N, 96.40°E), altitude 345 m, 1 March 2017, coll. J. Saini et al. (ZSI-C7134/2) GoogleMaps ; 4 males (cw 15.4–15.8 mm, cl 11.8-– 11.4 mm, ch 7.3–7.6 mm, fw 5.5–5.7 mm), 3 females (cw 13.6–16.4 mm, cl 10.2–13.1 mm, ch 5.7–7.1 mm, fw 4.7–5.7 mm), Hornbill camp (27.54°N and 96.44°E), altitude 657 m, 10 March 2017, coll. J. Saini et al. (ZSI-C7135/2) GoogleMaps .

Diagnosis. Carapace subquadrate, highly convex; dorsal surface glabrous, pitted, posterolateral margin longer than anterolateral margin ( Fig. 2A View FIGURE 2 ); cornea relatively large ( Fig. 2B View FIGURE 2 ), sixth abdominal somite subquadrate in shape ( Fig. 2C View FIGURE 2 ), G1 terminal segment relatively small, knife-shaped with semicircular to bluntly triangular dorsal flap, outer terminal margin almost straight, with short setae, tip not sharply pointed, groove for G2 medial ( Fig. 4A–D View FIGURE 4 , 5A–E View FIGURE 5 ).

Description of male holotype. Carapace broader than long, longitudinally convex; maximum width 1.3 times length at midline, height at middle of carapace 0.6 times length at midline; dorsal surface glabrous, pitted; anterolateral margin convex, granulated, shorter than posterolateral margin, with few horizontal and oblique striae on anterolateral region ( Fig. 2A View FIGURE 2 ); posterolateral margin slightly converging towards posterior, with short, oblique striae ( Fig. 2A View FIGURE 2 ); front broad, width 0.3 times maximum carapace width, gently deflexed ventrally, frontal margin distinctly bilobed, frontal median triangle incomplete; postorbital cristae rugose, not distinct, epigastric cristae well developed, rugose ( Fig. 2A View FIGURE 2 ); external orbital tooth small, blunt, outer margin oblique, straight, inner margin short; orbits ovate to subquadrate in outline, postorbital region slightly concave, smooth; epibranchial tooth almost obsolete; branchial region slightly swollen, cervical groove indistinct, mesogastric groove deep, long, “I”-shaped; “H”-shaped gastrocardiac groove deep, broad. Epistomal median tooth triangular, blunt. Eyes with short peduncle, corneas large. Antennular fossae broad, subrectangular.

Mandibular palp three-segmented. Ischium of third maxilliped subrectangular, 1.5 times longer than broad, median sulcus deep; merus subquadrate, little longer than half of breadth; exopod of third maxilliped reaching up to half length of merus, with short flagellum.

Chelipeds unequal; merus without inner distal tooth; carpus with sharp inner distal tooth; carpus, propodus with strongly rugose outer surface; fingers broad, shorter than palm, dentary edge with rows of conical teeth, major cheliped with two to three molariform teeth in dentary edge, narrow gap visible between fingers when closed; cheliped length almost equal to p2 and p4, p3 much longer; dactylus of p5 equal in length to propodus; dactylus slightly longer than propodus in p2–p4; in p3 and p4 propodus twice longer than breadth; margins of p2 and p3 lined with short setae.

Thoracic sternites smooth, randomly pitted, suture between thoracic sternites s1/ s2 distinct, deep, short straight line, reaching lateral margins; suture between s2/s3 not visible, except of two short lateral grooves; sutures between s3/s4 and s4/s5 distinct. Sternopleonal cavity deep, long, reaching up to imaginary line joining anterior part of cheliped coxae.

Pleon smooth, glabrous, broadly triangular, first somite shortest, second to sixth somites progressively longer; sixth somite rectangular, median length nearly half of its greatest width, lateral line straight, slightly convergent towards pleon; pleon slightly longer than broad, lateral margin straight, convergent anteriorly, apex rounded.

G1 terminal segment relatively short, ca. 0.4 times combined length of subterminal, terminal segments, slender, knife-shaped with semicircular to bluntly triangular dorsal flap, outer terminal margin almost straight, with short setae, tip triangular, blunt, groove for G2 medial in position ( Fig. 4A–D View FIGURE 4 ); subterminal segment broad, outer margin convex, inner margin slightly concave. G2 terminal segment distinctly longer than half of subterminal segment, slender; outer margin of subterminal segment gently convex ( Fig. 5A,B View FIGURE 5 ).

Live coloration. Carapace dark brown dorsally, ventral regions yellow, with green and olive patches on the pleon. Chelipeds orange brown, ambulatory legs brown ( Fig. 6A View FIGURE 6 ).

Variation. The male paratype (ZSI-C7129/2) is just smaller than the holotype, its chelipeds are amber yellow, left cheliped is larger than right, otherwise all the characters of carapace and gonopods are almost similar as holotype. The female paratype (ZSI-C7130/2) is ovigerous with about 50 eggs, each egg measuring an average of 1.6 mm in diameter, the pleon almost covers all of the sternites, except the anterior portion of sternite 1, gonopore large, situated at the junction below the suture between the fifth and sixth sternites ( Fig. 3 C,D View FIGURE 3 ).

Etymology. The new species is named after Stanley W. Kemp (1882–1945), former Superintendent of the Zoological Survey of India, for his valuable work on Indian carcinology, particularly that of Arunachal Pradesh, formerly known as Abor country ( Kemp, 1913).

Remarks. Potamon (Geotelphusa) adiatretum Alcock, 1909 , was described by Alcock (1909a) based on material from three different localities in what is now Myanmar, including the syntypes from Moulmein (ZSI- C6966/3). Later, Kemp (1913) collected a good number of specimens from Yembung and adjacent areas in the Abor Hills (in what is now Arunachal Pradesh), which he still considered to be P. (G.) adiatretum , despite noting several morphological differences from the types, considering them to be merely intra-specific variation. Bott (1970) also collected one male (MKa 8018/10) from the same locality in India, and transferred the species to his new genus, Tiwaripotamon . Subsequently Yeo & Ng (2007) reassigned this species to a new, monotypic genus, Teretamon , based on their examination of the syntypes and fresh material from Myanmar. While re-examining the specimens from Yembung collected by Kemp (1913: pl. 18 figs. 10–12) and the figures by Bott (1970: pl. 38 fig. 20, pl. 45 fig. 18), we noted that they are sufficiently different from T. adiatretum (cf. Alcock 1910: pl. 3 fig. 11a, b; Yeo & Ng 2007: fig. 13a–c), and are very much like the present material from Namdapha, and are therefore considered here as Teretamon kempi n. sp. Recently, two additional species of Teretamon were described from northeastern India: T. indicum Mitra, 2017 , from Mizoram, and T. spelaeum, Absar, Mitra & Kharkongor, 2017 , a semi-stygobitic species from Meghalaya.

Teretamon kempi n. sp. is distinguished from T. adiatretum (Alcock, 1909) by the following morphological characters: the anterolateral margin of the carapace is distinctly cristate and granulate in T. kempi n. sp. ( Fig. 2A View FIGURE 2 ) (vs. anterolateral margin of carapace not distinctly cristate and smooth in T. adiatretum ; cf. Alcock 1910: pl. 3 fig. 11a, b; Yeo & Ng 2007: fig. 13a); the anterolateral margin is distinctly shorter than the posterolateral margin ( Fig. 2A View FIGURE 2 ) (vs. anterolateral margin slightly shorter than posterolateral margin in T. adiatretum ; cf. Alcock 1910: pl. 3 fig. 11; Yeo & Ng 2007: fig. 13a); the cornea is relatively large in T. kempi n. sp. ( Fig. 2B View FIGURE 2 ) (vs. cornea relatively small in T. adiatretum ; cf. Yeo & Ng 2007: fig. 13b); the upper orbital border is curved in T. kempi n. sp. ( Fig. 2B View FIGURE 2 ) (vs. upper orbital border obliquely straight in T. adiatretum ; cf. Yeo & Ng 2007: fig. 13b); the epistomal median tooth is widely triangular in T. kempi n. sp. ( Fig. 2B View FIGURE 2 ) (vs. epistomal median tooth narrowly triangular in T. adiatretum ; cf. Yeo & Ng 2007: fig. 13b); the carpal spine of the cheliped is sharp and narrowly triangular in T. kempi n. sp. ( Fig. 2A View FIGURE 2 ) (vs. carpal spine blunt, widely triangular in T. adiatretum ; cf. Alcock 1910: pl. 3, fig. 11; Yeo & Ng 2007: fig. 13a); in the major cheliped a relatively narrow gap forms between the base of fingers when closed in T. kempi n. sp. ( Fig. 2A View FIGURE 2 ) (vs. a wide gap between the base of fingers of major cheliped in T. adiatretum ; cf. Yeo & Ng 2007: fig. 13c); the terminal segment of the G1 is twisted at the base, the inner middle lateral part has a bluntly triangular dorsal flap, gradually narrowed toward the tip, tip not narrowly pointed in the new species ( Fig. 4 A–D View FIGURE 4 ) (vs. G1 terminal segment not twisted, dorsal flap of inner middle part acutely trianglular, tip narrowly pointed in T. adiatretum ; cf. Yeo & Ng 2007: fig. 13d).

The new species has several morphological similarities with T. indicum Mitra, 2017 , as both have a roughly quadrangular carapace, broad front, relatively short ambulatory legs, and a distinctly high carapace. The new species differs from T. indicum in the following morphological characters: the oblique striae are arranged in a continuous row on the posterolateral part of carapace in T. kempi n. sp. ( Fig. 2A View FIGURE 2 ) (vs. oblique striae are not continuous throughout the posterolateral border of carapace in T. indicum ; cf. Mitra 2017: figs. 58, 63); the postorbital cristae are not distinct in T. kempi n. sp. ( Fig. 2A View FIGURE 2 ) (vs. post orbital cristae quite distinct in T. indicum ; cf. Mitra 2017: fig. 58 & 63); the carpal spine of the cheliped is short and strong in T. kempi n. sp. ( Fig. 2A View FIGURE 2 ) (vs. carpal spine just like a granules in T. indicum ; cf. Mitra 2017: fig. 58, 63); the male pleon is distinctly longer than broad in T. kempi n. sp. ( Fig. 2C View FIGURE 2 ) (vs. pleon as long as broad in T. indicum ; cf. Mitra 2017: fig. 60); the lateral margins of the sixth pleonal segment are almost parallel in T. kempi n. sp. ( Fig. 2C View FIGURE 2 ) (vs. lateral margins convergent towards pleon in T. indicum ; cf. Mitra 2017: fig. 60); the terminal segment of the G1 is bluntly triangular and gradually narrowed toward the tip, and the tip is not sharply pointed in the new species ( Fig. 4 View FIGURE 4 A-D) (vs. G1 terminal segment subcylindrical, inner middle part laterally convex in a semicircular pattern, tip acutely pointed in T. indicum ; cf. Mitra 2017: fig. 116–119).

The new species differs from T. spelaeum Absar, Mitra & Kharkongor, 2017 , the only cave-dwelling potamid known from India, thus far, in the following morphological characters; the carapace is comparatively less wider than T. kempi n. sp. ( Fig. 2A View FIGURE 2 ) (vs. carapace much wider in T. spelaeum ; cf. Absar et al. 2017: figs. 2a, 4a); the outer surface of the cheliped is glabrous, with only some striae on the outer surface of the propodus, in T. kempi n. sp. ( Fig. 2A View FIGURE 2 ) (vs. outer surface of cheliped with long setae in T. spelaeum ; cf. Absar et al. 2017: fig. 2d); the orbit is almost subquadrate in T. kempi n. sp. ( Fig. 2B View FIGURE 2 ) (vs. orbit subtriangular in T. spelaeum ; cf. Absar et al. 2017: fig. 2b); the antennular fossae are relatively narrow in T. kempi n. sp. ( Fig. 2B View FIGURE 2 ) (vs. antennular fossae relatively broad in T. spelaeum ; cf. Absar et al. 2017: fig. 2b); the eyes have large corneas in T. kempi n. sp. ( Fig. 2B View FIGURE 2 ) (vs. eyes with small corneas in T. spelaeum ; cf. Absar et al. 2017: fig. 2b); the eyestalk is short and cylindrical in T. kempi n. sp. ( Fig. 2B View FIGURE 2 ) (vs. eye stalkstout, triangular with broad base in T. spelaeum ; cf. Absar et al. 2017: fig. 2b); and the G1 terminal segment has a triangular dorsal flap ( Fig. 4A–D View FIGURE 4 ) (vs. G1 terminal segment with semicircular dorsal flap in T. spelaeum ; cf. Absar et al. 2017: fig. 3c,d). Furthermore, T. kempi n. sp. inhabits hill stream habitats as do T. adiatretum and T. indicum , but but T. spelaeum is a semi-stygobitic species ( Absar et al. 2017).

Ecology & distribution. All the specimens of the new species were collected from primary dipterocarp forests with thick canopy cover ( Fig. 6C View FIGURE 6 ), and from elevations of 375–657 m above sea level. Most of the individuals were observed under rocks and a few under leaf litter along dried or partially dry streams or close by ( Fig. 6B View FIGURE 6 ). The crabs retreated into their small, shallow burrows underneath rocks, when disturbed. In some cases multiple individuals were seen under the same rock. During the field survey in March 2017, several brooding females were observed and some were collected. None of the individuals observed during the other seasons were reproductively active, suggesting that T. kempi n. sp. breeds before or at the onset of monsoon season in Namdapha. In Deban and Lankhai naala, an unidentified species belonging to the family Gecarcinucidae was also observed with T. kempi n. sp. under the same rocks.

Teretamon kempi n. sp. i s known only from the Namdapha Tiger reserve of Changlang district of Arunachal Pradesh .