Karkata kusumbha, Pati & Rajesh & Raj & Sheeja & Kumar & Sureshan, 2017

Pati, S. K., Rajesh, L., Raj, Smrithy, Sheeja, V. U., Kumar, A. Biju & Sureshan, P. M., 2017, Karkata, a new genus of gecarcinucid freshwater crab with two new species, and four new species of Pilarta Bahir and Yeo, 2007 and Cylindrotelphusa Alcock, 1909 (Decapoda: Brachyura) from Kerala, India, Journal of Natural History (J. Nat. Hist.) 51 (23 - 24), pp. 1295-1330 : 1305-1307

Karkata kusumbha sp. nov.

( Figures 4 (a–i), 5(a–d) and 6(c,d))

Type specimens

Holotype: male (cw 28.12 mm, cl 21.50 mm, ch 13.85 mm, fw 9.34 mm), Thaalumkandam , near Mankulam, Idukki district, Kerala, India (10.110°N, 76.905°E; altitude 793 m), 21 January 2016, coll. Smrithy Raj and L. Rajesh (ZSI, WRC-C.1527) . Paratypes: 2 males (cw 25.57–29.55 mm, cl 19.94–22.51 mm, ch 13.42–15.61 mm, fw 8.52–9.88 mm), 1 female (cw 17.64 mm, cl 13.84 mm, ch 9.55 mm, fw 6.05 mm), same data as holotype (ZSI, WRC-C.1528) .

Diagnosis

Carapace slightly broader than long (cw/cl = ca. 1.3), deep (ch/cl = ca. 0.6–0.7), orangered coloured; dorsal surface smooth except epigastric and postorbital cristae, and lateral margins; anterolateral margin with few short, oblique striae; posterolateral margin with long, oblique striae; front slightly broad, smooth or slightly rugose; epigastric and postorbital cristae well developed; external orbital angle acutely triangular; epibranchial tooth small, blunt; cervical grooves distinct; H-shaped groove deep ( Figure 4 (a,b)). Sutures between male thoracic sternites s2/s3 and s3/s4 prominent as deep grooves ( Figure 4 (c,g)). Male abdomen T-shaped; sixth abdominal somite nearly as long as broad, longer than telson ( Figure 4 (c,h)). G1 almost straight; terminal segment cone-shaped, very short, ca. 0.2 times length of subterminal segment; basal half of subterminal segment with distinctly concave outer margin ( Figure 5 (a–c)). G2 with short distal segment, ca. 0.3 times length of basal segment ( Figure 5 (d)).

Description of male holotype

Carapace slightly broader than long (cw/cl = 1.3), deep (ch/cl = 0.6); dorsal surface slightly convex in frontal view, smooth except epigastric and postorbital cristae, and lateral margins; anterolateral surface slightly inflated in frontal view; anterolateral margin short, with few short, oblique striae; posterolateral margin with long, oblique striae; front smooth; frontal margin almost straight, slightly broad (fw/cw = 0.3); epigastric cristae distinct; postorbital cristae distinct, sharp, reaching rugose epigastric cristae; external orbital angle acutely triangular, outer margin short, ca. 2 times length of inner margin; epibranchial tooth small, slightly sharp, separated from external orbital angle by distinct cleft; postorbital region strongly concave; branchial regions inflated, with distinct striae adjacent to lateral margins; subhepatic region rugose; cervical grooves distinct, shallow, broad, discontinuous, not reaching up to postorbital cristae; mesogastric groove deep, long, narrow, bifurcated posteriorly; H-shaped groove distinct, deep; frontal median triangle incomplete, with cristate dorsal margin only, lateral margins not developed; epistome posterior margin with prominent, triangular median lobe, almost straight lateral lobes ( Figure 4 (a,b)).

Chelipeds unequal, left chela larger; fingers of major cheliped with 10 or 11 large, blunt teeth, small gape when their tips in contact; outer surface of carpus rugose; major tooth of carpus long, sharp; outer surface of merus rugose ( Figure 4 (a,c–e)).

Ambulatory legs long, slender, with only scattered setae; dactylus (p2–p5) longer than propodus; longest propodus (p3) 2.5 times as long as broad ( Figure 4 (a,f)).

Suture between thoracic sternites s2/s3 prominent, deep, not reaching lateral margins, suture between sternites s3/s4 prominent, deep, reaching lateral margins ( Figure 4 (c,g)).

Abdomen T-shaped; fifth abdominal somite distinctly broader than long; sixth abdominal somite nearly as long as broad, longer than telson, with almost straight lateral margins; telson broadly triangular, as long as broad, with straight lateral margins, apex round; sternoabdominal cavity deep, long, extending up to imaginary line joining median part of cheliped coxae ( Figure 4 (c,h)).

Mandibular palp with 2 segments, terminal segment bilobed. First, second maxillipeds each with long flagellum on exopod. Third maxillipeds cover most of buccal cavity when closed; ischium subrectangular, longer than broad, with indistinct median sulcus; merus subrectangular, broader than long; exopod longer than ischium, reaching lower third of merus, lacking flagellum ( Figure 4 (i)).

G1 almost straight; terminal segment cone-shaped, very short, ca. 0.2 times length of subterminal segment; subterminal segment with almost straight inner margin and distinctly concave basal half outer margin ( Figure 5 (a–c)). G2 with short distal segment, ca. 0.3 times length of basal segment ( Figure 5 (d)).

Live colour

The dorsal surface of the carapace is dark orange-red, and ventral surface of the carapace, chelipeds and ambulatory legs are orange-red.

Paratypes

The male paratypes (ZSI, WRC-C.1528) are almost identical to the holotype in carapace morphology and gonopod structure except for the blunt epibranchial teeth in the smaller male (vs slightly sharp) and larger right chela in the bigger male (vs larger left chela).

The paratype female (ZSI, WRC-C.1528) is much smaller in size than the holotype and still immature. However, it is almost similar to the holotype in non-sexual characters. The only exceptions are its slightly rugose front and blunt epibranchial tooth. Its abdomen is triangular, not greatly expanded ( Figure 6 (c)). The vulvae are orbicular, very small, occupying nearly a quarter of the length of thoracic sternite 6, situated distantly from the margin with thoracic sternite 5, surrounded by a low rim and completely covered by a soft operculum ( Figure 6 (d)).

Etymology

The species epithet, kusumbha (Sanskrit for ‘safflower’), alludes to the orange-red colouration of the live crabs that resemble the colour of the flowers of safflower. Used as a noun in apposition.

Type locality

Thaalumkandam , near Mankulam, Idukki district, Kerala, India (10.110°N, 76.905°E; altitude 793 m) .

Remarks

The new species is closely related to K. ghanarakta in many carapace and gonopod features. Besides the shape of the G1 subterminal segment, the live colouration of the crab is characteristic for the species. For differences between the two species, see remarks for K. ghanarakta .

Ecological notes

Karkata kusumbha was found under the cobblestones of a small stream (1 m wide, about 1 foot deep). Crabs were also seen in burrows dug into loose soil (approximately 0.5 m deep) away from water bodies. According to the local people, crabs of this species are often seen wandering on the ground when their burrows are completely filled with water during the rainy season.

Geographic distribution

Karkata kusumbha sp. nov. is known only from the type locality, Thaalumkandam, which is a part of the Western Ghats in Idukki district of Kerala .

Key to the species of Karkata

1. Carapace maroon in life; basal half of G1 subterminal segment with almost straight outer margin........................................................................................ Karkata ghanarakta sp. nov.

– Carapace orange-red in life; basal half of G1 subterminal segment with distinctly concave outer margin........................................................................ Karkata kusumbha sp. nov.

Figures

Figure 4. Karkata kusumbha sp. nov., holotype male (ZSI, WRC-C.1527). (a) Dorsal view; (b) frontal view; (c) ventral view; (d) left or major cheliped; (e) carpus of major cheliped; (f) right ambulatory leg (p3); (g) anterior thoracic sternites (s1–s4); (h) abdominal somites 5, 6 and telson; (i) left third maxilliped. Scale bars: a–c = 10 mm; d, f = 5 mm; e, g–i = 2 mm.

Figure 5. Karkata kusumbha sp. nov., holotype male (ZSI, WRC-C.1527). (a) Dorsal view of left G1; (b) dorsal view of left G1 terminal segment; (c) ventral view of left G1; (d) left G2. Scale bars: a, c, d = 1 mm; b = 0.5 mm.

Figure 6. Abdomen and thoracic sternites of female paratypes. (a, b) Adult female paratype of Karkata ghanarakta gen. et sp. nov. (ZSI, WRC-C.1526); (c, d) juvenile female paratype of Karkata kusumbha sp. nov. (ZSI, WRC-C.1528); (e, f) sub-adult female paratype of Pilarta punctatissima sp. nov. (ZSI, WRC-C.1532); (g, h) adult female paratype of Cylindrotelphusa breviphallus sp. nov. (ZSI, WRC-C.1535); (i, j) adult female paratype of Cylindrotelphusa longiphallus sp. nov. (ZSI, WRC-C.1537). (a, c, e, g, i) abdomen; (b, d, f, h, j) thoracic sternites. Scale bars: a, b, g–j = 5 mm; c–f = 2 mm.