Rajathelphusa brunnea, Raj & Kumar & Ng, 2022
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publication ID |
https://doi.org/ 10.6620/ZS.2022.61-49 |
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persistent identifier |
https://treatment.plazi.org/id/03C97405-6562-FFF1-0718-F8F3383687CC |
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treatment provided by |
Felipe |
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scientific name |
Rajathelphusa brunnea |
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Rajathelphusa Raj, Kumar & Ng, 2021 View in CoL
Rajathelphusa brunnea sp. nov. ( Figs. 7 View Fig , 8A, 11A View Fig , 12A View Fig ) urn:lsid:zoobank.org:act:FC137752-02F7-4853-84D5-5559434CFD49
Material examined: Holotype: male (30.2 ×
22.6 mm) (DABFUK/AR-BR-117), Mattupetty, Idukki, Kerala, India, coll. S. Raj, 24 April 2018. Paratypes: 2 males (33.9 × 25.9 mm, 23.6 × 18.6 mm) (DABFUK/ AR-BR-118-119); 4 females (34.0 × 25.2 mm, 30.0 × 22.9 mm, 27.6 × 21.0 mm, 24.1 × 18.6 mm) (DABFUK/ AR-BR-120-123), Mattupetty, Idukki, Kerala, India, coll. S. Raj, 27 October 2021.
Comparative material: Rajathelphusa ala Raj, Kumar & Ng, 2021 Holotype: male (27.0 × 20.9 mm) (DABFUK/AR-BR-99/ZSI/WGR/IR.INV,/15361), Rajakumari, Idukki district, Kerala, 9.966911°N, 77.129715°E, coll. 2016. Rajathelphusa muni Raj, Kumar & Ng, 2021 Holotype: male (30.2 × 22.6 mm) (DABFUK/AR-BR-115) Kovilkadavu, Idukki district, Kerala (10.261413°N, 77.183799°E) coll. 2016.
Diagnosis: Carapace frontal region relatively wider ( Figs. 8C, 11E View Fig ); external orbital tooth with outer margin gently sinuous to almost straight ( Figs. 7 View Fig , 8A, B, 11A, B View Fig ); male pleonal somite 6 subquadrate, with almost straight lateral margins, telson with concave lateral margins ( Figs. 9C, 11D View Fig ). G1 terminal segment relatively long, conical, curved outwards, surface lined with long and short setae, gradually tapering to truncate tip, ca. 0.2 times length of subterminal segment ( Figs. 10A–C View Fig , 11F View Fig ).
Description of male holotype: Carapace broader than long, width ca. 1.3 times length; high, inflated in frontal view, dorsal surface convex ( Figs. 7 View Fig , 8A, B, 11A, B View Fig ). Frontal region relatively wider, surface smooth with low flattened granules ( Figs. 8C, D, 11E View Fig ); lateral parts of anterolateral and posterolateral regions with prominent short oblique striae, margins smoother does not appear serrated ( Figs. 7 View Fig , 8A, B, 11A, B View Fig ); suborbital with scattered granules and striae; pterygostomial regions with distinct low granules of different sizes on margins, glabrous, separated from other regions by low ridge; sub-brachial regions with numerous short striae ( Figs. 8C, 11E View Fig ). Epigastric cristae low but distinct, not cristate, medially separated by shallow inverted Y-shaped furrow, slightly anterior of postorbital cristae; postorbital cristae distinct, raised, not sharp, confluent with epigastric cristae, joining lateral margin as granules and interrupted striae ( Figs. 7 View Fig , 8A, B, C, 11A, B, E View Fig ). Cervical grooves distinct, not broad, joining prominent H-shaped and brachial grooves ( Figs. 7 View Fig , 8A, B, 11A, B View Fig ) External orbital tooth low, outer margin gently sinuous to almost straight, almost 3 times longer than inner margin; epibranchial tooth small, separated from external orbital tooth by a cleft, positioned above external orbital tooth in frontal view ( Figs. 7 View Fig , 8A, B, 11A, B View Fig ). Anterolateral margin distinctly convex, uneven, striae gives the impression of being serrated margins ( Figs. 7 View Fig , 8A, B, 11A, B View Fig ). Posterolateral margins gently concave, gently converging to almost straight or gently sinuous posterior carapace margin ( Figs. 7 View Fig , 8A, B, 11A, B View Fig ). Orbits subovate, oblique in frontal view; eyes filling up most of orbital space, eye peduncle moderately long, stout; cornea large, pigmented ( Figs. 8C, D, 11E View Fig ). Supraorbital margin sinuous, complete; suborbital margin concave ( Figs. 8C, D, 11E View Fig ). Antennae short, not reaching cornea of eyes; antennules folding transversely in longitudinally narrow fossa ( Figs. 8C, D, 11E View Fig ). Posterior margin of epistome with distinct median triangular tooth, separated from lateral concave lobe by distinct gape ( Figs. 8C, D, 11E View Fig ). Mandibular palp distinctly 2-segmented, terminal article bilobed. Third maxilliped ischium subrectangular, with distinct median sulcus; merus subquadrate, with raised margins, median part depressed; exopod slender, not reaching mid length of merus, flagellum long, reaching about entire width of merus ( Figs. 9A, B, 11C View Fig ). Chelipeds distinctly asymmetrical ( Figs. 7 View Fig , 8A, 9D). Dorsal margin of merus with strong striae, appears unevenly serrated, ventral margin with low granules ( Figs. 7 View Fig , 8A, 9D). Outer surface of carpus rugose, distal angle with prominent sharp tooth with basal tubercle ( Figs. 7 View Fig , 8A, 11A View Fig ). Outer surface of chelae unevenly granulated, granules scattered; fingers of major chelae curved with median proximal gape when fingers closed; cutting margin with large teeth and denticles; fingers of minor chelae straighter, similar to those of major chelae except more slender, without gape ( Fig. 9D). Ambulatory legs slender, not elongate; P3 longest, P5 shortest ( Figs. 7 View Fig , 8A, 11A View Fig ). Merus with sharp dorsal and ventral margins, not cristate, margins unevenly serrate but low; carpus with low median crest; propodus subrectangular with longitudinal median crest, ventral margin serrate; dactylus elongate, gently curved, lined with sharp spines ( Figs. 7 View Fig , 8A, 11A View Fig ). Anterior thoracic sternum transversely narrow; sternite 1 and 2 completely fused to form triangular plate with convex lateral margins, separated from sternite 3 by shallow, median groove, otherwise fused; sternite 3 and 4 fused, demarcated by shallow oblique grooves; dense short setae on grooves between sternite 2 and 4. Sutures between sternites 4/5, 5/6 and 6/7 medially interrupted, separated by narrow space; sternite 8 completely covered by closed pleon ( Figs. 9B, 11F, G View Fig ). Sternopleonal cavity deep, narrow, reaching to imaginary line joining median points of cheliped coxae ( Figs. 9B, 11F View Fig ). Male pleonal-locking tubercle low, round, positioned on distal third of sternite 5 ( Fig. 11F View Fig ). Penis on condyle of coxa of fourth ambulatory leg. Pleon triangular, all somites and telson free; somite 1 and 2 longitudinally narrow, subequal in width, both less wide than somite 3; somite 3 trapezoidal, reaching to coxae of fourth ambulatory legs; somites 4 and 5 trapezoidal; somite 6 subquadrate, with sinuous lateral margins; slightly wider than long; telson triangular with gently concave lateral margins ( Figs. 9C, 11D, G View Fig ). G1 almost straight, groove for G2 ventral in position; terminal and subterminal segments clearly demarcated by membranous suture; subterminal segment with proximal part broader, gradually tapering to more slender distal half, outer margin gently sinuous, terminal segment relatively longer, conical and gently curved outwards, surface lined with rows of long and short setae, gradually tapering to truncate tip, ca. 0.2 times length of subterminal segment ( Figs. 10A–C View Fig , 11F View Fig ). G2 as long as G1 ( Fig. 10D View Fig ).
Females: The adult paratype female specimens (largest 34.0 × 25.2 mm) (DABFUK/AR-BR-120) resemble the holotype in most non-sexual characters, except they have relatively smaller and more slender chelae. The pleon is ovate, with all somites and telson free, covering most of the thoracic sternum, except the lateral edges ( Fig. 12A, B View Fig ). The vulvae on sternite 6 is large, subovate, and positioned adjacent to sternite 5, the opening being membranous without any sternal vulvar cover ( Fig. 12C View Fig ).
Variations: The paratype males agree with the holotype in most aspects. The distal segment of G2 varies in shape, from straight to slightly curved in the two specimens examined.
Colour: In life most of the carapace and legs are dark brown to brown in colour, tips of fingers and legs are yellowish orange in colour. Ventral side of the body yellowish orange to dirty white in colour ( Fig. 7 View Fig ).
Etymology: The name is derived from the Latin for dark brown, alluding to the overall dark colour of the new species alive.
Remarks: The genus Rajathelphusa currently contains two species R. ala Raj, Kumar & Ng, 2021 , and R. muni Raj, Kumar & Ng, 2021 (cf. Raj et al. 2021). The new species differs from R. ala in that the chelipeds and ambulatory legs are dark reddish brown in life ( Figs. 7 View Fig , 11A View Fig ) (versus chelipeds and ambulatory legs pale orange; cf. Raj et al. 2021: figs. 2A, 5A); anterolateral margin is smoother and does not appear serrate ( Figs. 8A, B, 11A, B View Fig ) (versus striae on anterolateral margin stronger with the margin uneven to gently serrate; cf. Raj et al. 2021: figs. 3A, 4A, B); the ischium of the third maxilliped is proportionately longer ( Figs. 9A, 11C View Fig ) (versus more quadrate; cf. Raj et al. 2021: fig. 4D); the median lobe of the posterior margin of the epistome has the lateral margin almost straight ( Figs. 8C, D, 11E View Fig ) (versus gently convex; cf. Raj et al. 2021: fig. 4C); and the overall G1 is more slender and more elongate, and significantly, the terminal segment is proportionately longer ( Figs. 10A–C View Fig , 11F View Fig ) (versus G1 overall relatively shorter and stouter; cf. Raj et al. 2021: fig. 9B–D). Rajathelphusa brunnea sp. nov. differs from R. muni in that the carapace is reddish brown with the chelipeds and ambulatory legs are dark reddish brown in life ( Figs. 7 View Fig , 11A, B, F, G View Fig ) (versus carapace dark brown with the chelipeds and ambulatory legs pale orange; cf. Raj et al. 2021: fig. 8); the ischium of the third maxilliped is proportionately longer ( Figs. 9A, 11C View Fig ) (versus more quadrate; cf. Raj et al. 2021: fig. 7D); the lateral margins of the male telson are gently concave ( Fig. 9B, C, 11D, G View Fig ) (versus deeply concave; cf. Raj et al. 2021: fig. 7E, F); the lateral margin of male somite 6 is sinuous ( Figs. 9C, 11D, G View Fig ) (versus almost straight with the somite appearing rectangular; cf. Raj et al. 2021: fig. 7E); the median lobe of the posterior margin of the epistome has the lateral margin almost straight ( Figs. 8C, D, 11E View Fig ) (versus gently convex; cf. Raj et al. 2021: fig. 7C); and the overall G1 is more slender and more elongate, and significantly, the terminal segment is proportionately longer and gently curved outwards ( Figs. 10A–C View Fig , 11F View Fig ) (versus G1 overall relatively shorter and stouter with the terminal segment vertical; cf. Raj et al. 2021: fig. 9F–H).
Distribution: The species is known only from Mattupetty (10.108618°N, 77.134830°E), a tourist village in Idukki district of Kerala state ( Figs. 1 View Fig , 13A–F View Fig ).
Ecology: The species lives in deep burrows away from a natural stream that empties into the Mattupetty dam ( Fig. 13F View Fig ). The holes are very deep and the hole connects to underground water channels. We observed some holes with branches at the entrance leading to a very deep pit. No crabs were noticed to live in shallow holes. The species could not be lured out with animal bait. The current location is famous for the Meowing Night Frog, Nyctibatrachus poocha ( Biju et al. 2011) (family Nyctibatrachidae ), the distinctive sound of the frogs echoing throughout the night.
Additional remarks: Locals in the type locality use the crabs as medicine, and it is supposed to be effective in treating severe coughs for children. The crabs are cleaned, crushed and then boiled with spices before being consumed. As the type locality is very close to a public road, there are many potential threats for the new species since it is known thus far from only a small geographical area. Human activities can quickly impact the entire region, and therefore, the species must be regarded as vulnerable, and a careful assessment of its conservation status is urgently needed.
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