Pilarta punctatissima, 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 : 1314-1317

Pilarta punctatissima sp. nov.

( Figures 6 (e,f), 9(a–i) and 10(a–d))

Type specimens

Holotype: male (cw 13.61 mm, cl 9.43 mm, ch 5.70 mm, fw 3.59 mm), Ovumkal , Thattekkad Bird Sanctuary, Ernakulam district, Kerala, India (10.115°N, 76.702°E; altitude 46 m), 27 October 2015, coll. K.G. Emiliyamma (ZSI, WRC-C.1531).

Paratypes: 2 females (cw 9.93–13.22 mm, cl 7.32–9.25 mm, ch 4.19–5.41 mm, fw 3.19– 3.61 mm), same data as holotype (ZSI, WRC-C.1532) .

Diagnosis

Carapace broader than long (cw/cl = ca. 1.4), densely punctate; dorsal surface convex in frontal view, smooth except epigastric and postorbital cristae, postorbital region, frontal region and lateral margins; anterolateral and posterolateral margins with dense setae; front slightly broad (fw/cw = ca. 0.3); epigastric and postorbital cristae visible, rugose but not well developed; external orbital angle broadly triangular, with long outer margin, ca. 4 times length of inner margin; epibranchial tooth very small, blunt; branchial regions inflated, with distinct, thick striae adjacent to lateral margins; cervical grooves distinct, broad; H-shaped groove shallow; epistome posterior margin with broadly triangular median lobe, medially notched lateral lobes ( Figure 9 (a,b)). Ambulatory legs with dense setae on external surfaces of dactylus, propodus and carpus ( Figure 9 (a,f)). Sutures between male thoracic sternites s2/s3 and s3/s4 undiscernible as grooves ( Figure 9 (c,g)). Male abdomen broadly T-shaped; sixth abdominal somite slightly shorter than telson; telson as long as broad ( Figure 9 (c,h)). G1 terminal segment more stout, short, ca. 0.3 times length of subterminal segment, with strongly convex outer margin, tip distinctly narrow, straight; subterminal segment with broad median portion, almost same width as widest part of base, outer margin convex ( Figure 10 (a–c)). G2 with very long distal segment, ca. 0.6 times length of basal segment ( Figure 10 (d)).

Description of male holotype

Carapace broader than long (cw/cl = 1.4), densely punctate; dorsal surface convex in frontal view, smooth except epigastric and postorbital cristae, postorbital region, frontal region and lateral margins; anterolateral surface slightly inflated in frontal view; anterolateral and posterolateral margins with dense setae; frontal margin bilobed, slightly broad (fw/cw = 0.3); epigastric and postorbital cristae visible, rugose but not well developed; external orbital angle broadly triangular, outer margin long, ca. 4 times length of inner margin; epibranchial tooth very small, blunt; postorbital region concave; branchial regions inflated, with distinct, thick striae adjacent to lateral margins; cervical grooves distinct, broad; epigastric groove short, broad; mesogastric groove deep, short, broad; H-shaped groove distinct, shallow; frontal median triangle incomplete, with cristate dorsal margin only, lateral margins not developed; epistome posterior margin with prominent, broadly triangular median lobe, medially notched lateral lobes ( Figure 9 (a,b)).

Chelipeds unequal, right chela larger; fingers of larger cheliped gaping when fingers closed; outer surface of carpus rugose; major tooth of carpus large, broad, blunt; external surfaces of carpus and palm of smaller cheliped with dense setae ( Figure 9 (a,c–e)).

Ambulatory legs long, moderately stout, with distinct setae; p3 longest; external surfaces of dactylus, propodus and carpus with dense setae ( Figure 9 (a,f)).

Sutures between thoracic sternites s2/s3 and s3/s4 undiscernible as grooves ( Figure 9 (c,g)).

Abdomen broadly T-shaped; fifth abdominal somite distinctly broader than long; sixth abdominal somite broader than long, slightly shorter than telson; telson as long as broad, apex round; sternoabdominal cavity deep, long, extending up to imaginary line joining anterior part of cheliped coxae ( Figure 9 (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 subquadrate, slightly broader than long; exopod longer than ischium, reaching lower third of merus, lacking flagellum ( Figure 9 (i)).

G1 stout, straight; terminal segment more stout, short, ca. 0.3 times length of subterminal segment, with strongly convex outer margin, tip distinctly narrow, straight; subterminal segment with broad median portion, almost same width as widest part of base, outer margin convex ( Figure 10 (a–c)). G2 with very long distal segment, ca. 0.6 times length of basal segment ( Figure 10 (d)).

Live colour

Carapace, chelipeds and ambulatory legs are all dark brown.

Paratypes

The female paratypes (ZSI, WRC-C.1532) are similar to the holotype in most non-sexual characters. Their chelipeds, however, are almost equal in size and densely setose on the external surface of the palm as compared to the larger and smooth right chela of the holotype. The abdomen of the bigger or sub-adult female is broadly ovate, covering most of the sternum except thoracic sternite 3 and lateral surfaces ( Figure 6 (e)) whereas that of the smaller or juvenile female is comparatively less broad. The vulvae are orbicular, large, occupying nearly half the length of thoracic sternite 6, situated slightly away from the margin with thoracic sternite 5, surrounded by a raised rim and completely covered by a soft operculum ( Figure 6 (f)).

Etymology

The species epithet, punctatissima , is derived from the Latin for ‘most punctate’, referring to the densely punctate carapace of the crab.

Type locality

Ovumkal , Thattekkad Bird Sanctuary, Ernakulam district, Kerala, India (10.115°N, 76.702°E; altitude 46 m) .

Remarks

The new species, Pilarta punctatissima , differs from its congeners ( P. aroma sp. nov. and P. anuka ) by the densely punctate carapace (vs sparsely punctate), densely setose anterolateral and posterolateral margins of the carapace (vs glabrous), epistome posterior margin with medially notched lateral lobes (vs with distinctly sinuous lateral lobes), sixth male abdominal somite slightly shorter than telson (vs longer than telson), male telson as long as broad (vs broader than long), more stout G1 terminal segment (vs less stout), and comparatively long G2 distal segment, ca. 0.6 times the length of the basal segment (vs relatively short G2 distal segment, ca. 0.4–0.5 times the length of the basal segment) ( Figures 7 (a–c,h) and 8(b,d) for P. aroma ; Figures 9 (a–c,h) and 10(b,d) for P. punctatissima ; see Bahir and Yeo 2007, figs 25(a,d,f,h) and 26(a–c) for P. anuka ).

In addition, P. punctatissima can be separated from P. anuka by the relatively longer outer margin of the external orbital angle, ca. 4 times the length of the inner margin (vs relatively short outer margin of the external orbital angle, ca. 3 times the length of the inner margin) and strongly convex outer margin of the G1 terminal segment (vs slightly convex outer margin of the G1 terminal segment) ( Figures 9 (a) and 10(b) for P. punctatissima ; see Bahir and Yeo 2007, fig. 25(a,f) for P. anuka ). Additional differences between P. punctatissima and P. aroma are discussed under remarks for P. aroma .

Ecological notes

Pilarta punctatissima was found in a stream flowing across a marshy area shaped like a big ditch that is located inside a degraded semi-evergreen forest patch with profuse grassy vegetation and aquatic plants. Crabs were collected from the rocky crevices along the course of the stream.

Geographic distribution

The new species is known only from the Thattekkad Bird Sanctuary, which is a part of the Western Ghats in Ernakulam district of Kerala.

Key to the species of Pilarta

1. Carapace densely punctate, anterolateral and posterolateral margins densely setose; epistome posterior margin with medially notched lateral lobes; sixth male abdominal somite slightly shorter than telson; male telson as long as broad; G1 terminal segment more stout; G2 distal segment comparatively long, ca. 0.6 times length of basal segment............................................... ............................................... Pilarta punctatissima sp. nov.

- Carapace sparsely punctate, anterolateral and posterolateral margins glabrous; epistome posterior margin with distinctly sinuous lateral lobes; sixth male abdominal somite longer than telson; male telson broader than long; G1 terminal segment less stout; G2 distal segment comparatively short, ca. 0.4–0.5 times length of basal segment........................................................................................................................................................ 2

2. Postorbital cristae smooth; branchial regions lacking striae; H-shaped groove deep; G1 terminal and subterminal segments with almost straight outer margin, terminal segment relatively long, ca. 0.4 times length of subterminal segment................................ ............................................................................................................................... Pilarta aroma sp. nov.

- Postorbital cristae rugose; branchial regions with distinct striae; H-shaped groove shallow; G1 terminal and subterminal segments with convex outer margin, terminal segment relatively short, ca. 0.3 times length of subterminal segment............................... ....................................................................................................... Pilarta anuka Bahir and Yeo, 2007

Figures

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.

Figure 7. Pilarta aroma sp. nov., holotype male (ZSI, WRC-C.1529). (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 4–6 and telson; (i) left third maxilliped. Scale bars: a–c = 10 mm; d, f = 5 mm; e, g–i = 2 mm.

Figure 9. Pilarta punctatissima sp. nov., holotype male (ZSI, WRC-C.1531). (a) Dorsal view; (b) frontal view; (c) ventral view; (d) right or major cheliped; (e) carpus of major cheliped; (f) right ambulatory leg (p3); (g) anterior thoracic sternites (s1–s4); (h) abdominal somites 4–6 and telson; (i) left third maxilliped. Scale bars: a–c = 10 mm; d, f = 5 mm; e, g–i = 2 mm.

Figure 10. Pilarta punctatissima sp. nov., holotype male (ZSI, WRC-C.1531). (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.