Vanni ashini Bahir & Yeo, 2007

Vanni ashini Bahir & Yeo, 2007 View in CoL

[Discoverer forest crab]

( Figs. 20 View FIGURE 20 , 21 View FIGURE 21 )

Vanni ashini Bahir & Yeo, 2007: 343 View in CoL , figs. 39, 40.

Vanni ashini View in CoL – Rajesh et al. 2017: 146, fig. 27.—Pati 2020: 162 (list).— Pati & Pradhan 2020: 555836 (list).

Type material examined. Holotype: male ( CW 24.1 mm, CL 18.5 mm) ( ZRC 2003.0232 View Materials ), India, Kerala State, Thiruvananthapuram District, Ponmudi , 8.76872° N, 77.11047° E, elev. 975 m a.s.l., collector and collection date unknown. GoogleMaps

Other material examined. India – Kerala State: female ( CW 16.9 mm, CL 13.4 mm, CH 7.7 mm, FW 5.6 mm) ( ZSI-WGRC IR/INV/9158) , Thiruvananthapuram District , Bonacaud, Pandipath, 8.68071° N, 77.16733° E, elev. 547 m a.s.l., coll. K. Rajmohana, 15 December 2015 GoogleMaps . – Tamil Nadu State: male ( CW 16.5 mm, CL 12.9 mm, CH 7.3 mm, FW 5.4 mm) , female ( CW 15.3 mm, CL 12.0 mm, CH 6.8 mm, FW 5.1 mm) ( ZSI-WRC C.2322) , Kanyakumari District , Kalakad Mundanthurai Tiger Reserve , way to Muthukulivayal II Bend, 8.476° N, 77.383° E, elev. 994 m a.s.l., coll. Varadaraju, 16 February 2020 GoogleMaps ; female ( CW 23.0 mm, CL 16.7 mm, CH 10.3 mm, FW 6.6 mm) ( ZSI-WRC C.2323) , Tirunelveli District , Kalakad Mundanthurai Tiger Reserve , Kalakad Range , Sengaltheri, Tiger Cave, 8.523° N, 77.447° E, elev. 1170 m a.s.l., coll. R. Babu et al., 15 March 2022 GoogleMaps ; male ( CW 16.4 mm, CL 12.3 mm, CH 6.9 mm, FW 5.1 mm) , 3 females ( CW 21.0– 27.4 mm, CL 15.2–19.9 mm, CH 9.0– 11.8 mm, FW 6.1–7.9 mm) ( ZSI-WRC C.2166) , Tirunelveli District , Kalakad Mundanthurai Tiger Reserve, Kalakad Range , Shengaltheri , Karumandi Amman Kovil, Manimuthar River, 8.530° N, 77.446° E, elev. 983 m a.s.l., coll. R. Babu et al., 14 August 2019 GoogleMaps ; 2 males ( CW 19.4–23.6 mm, CL 14.3–17.0 mm, CH 8.3–9.7 mm, FW 5.7–6.9 mm) , 5 females ( CW 22.7–26.6 mm, CL 16.7–18.9 mm, CH 9.7–11.1 mm, FW 6.6–7.5 mm) ( ZSI-WRC C.2324) , Tirunelveli District , Kalakad Mundanthurai Tiger Reserve , Kalakad Range , Sengalteri, Kulirati, 8.531° N, 77.456° E, elev. 962 m a.s.l., coll. R. Babu et al., 16 March 2022 GoogleMaps ; male ( CW 14.3 mm, CL 11.2 mm, CH 6.5 mm, FW 4.8 mm) ( ZSI-WRC C.2167) , Tirunelveli District , Kalakad Mundanthurai Tiger Reserve , Ambasamudram Range, Marapalam, 8.544° N, 77.375° E, elev. 1169 m a.s.l., coll. R. Babu et al., 21 August 2019 GoogleMaps .

Diagnosis. Medium sized crabs (maximum CW 27.4 mm). Carapace relatively broad (CW/CL = ca. 1.3–1.4), relatively low ( CH /CW = ca. 0.4–0.5) ( Fig. 20A–C, E View FIGURE 20 ); external orbital angle triangular, with short outer margin, ca. 2 times length of inner margin ( Fig. 20A, B, E View FIGURE 20 ); epibranchial tooth low, discernible ( Fig. 20A, B, E View FIGURE 20 ); male sternopleonal cavity reaching to imaginary line joining submedial part of cheliped coxae ( Fig. 20D View FIGURE 20 ); male pleonal somite 6 subquadrate, slightly broad, proximal width ca. 1.1 times medial length, longer than telson, with strongly concave lateral margins ( Fig. 20D, G View FIGURE 20 ); male telson as long as broad, medial length ca. 1.0 times proximal width ( Fig. 20D, G View FIGURE 20 ); G1 relatively stouter ( Figs. 20H, I View FIGURE 20 , 21A, B View FIGURE 21 ); G1 ultimate article relatively stouter, gently curved outwards at ca. 10° from longitudinal axis of G1, relatively shorter, ca. 0.2 times length of penultimate article ( Figs. 20H, I View FIGURE 20 , 21A, B View FIGURE 21 ); G1 penultimate article with distal portion relatively less narrow than basal portion, outer margin gently sinuous ( Figs. 20H, I View FIGURE 20 , 21A, B View FIGURE 21 ); G2 longer than G1, ca. 1.2 times G1 length, ultimate article long, ca. 0.4 times length of penultimate article ( Figs. 20J View FIGURE 20 , 21C View FIGURE 21 ); vulvae subovate, relatively large, occupying ca. 0.6 times length of s6, located relatively close to s5/s6 ( Fig. 20K View FIGURE 20 ).

Remarks. Vanni ashini was reported by Pati et al. (2014) at a lower elevation (118 m a.s.l.) of the central Western Ghats, north of the Palghat Gap, in the Palakkad district of Kerala, which is an erroneous record as evident from their figures (Pati et al. 2014: pl. 2 figs. 7–9, pl. 4 figs. 3–5). Its occurrence there is highly unlikely as the species lives at the relatively higher elevations of the southern Western Ghats (see ecological notes and geographic distribution below).

Vanni ashini can be distinguished from the other species of the same genus by the low but distinct epibranchial tooth ( Fig. 20A, B, E View FIGURE 20 ) (versus epibranchial tooth indiscernible; Figs. 14A View FIGURE 14 , 16A View FIGURE 16 , 18A, B, E View FIGURE 18 ); the longer male pleonal somite 6 as compared to telson length ( Fig. 20D, G View FIGURE 20 ) (versus male pleonal somite 6 as long as telson; Figs. 14C, E View FIGURE 14 , 16C, H View FIGURE 16 , 18D, G View FIGURE 18 ); the male telson being equally long as broad, the medial length ca. 1.0 time the proximal width ( Fig. 20D, G View FIGURE 20 ) (versus male telson longer than broad, the medial length ca. 1.1–1.3 time the proximal width; Figs. 14C, E View FIGURE 14 , 16C, H View FIGURE 16 , 18D, G View FIGURE 18 ); and the relatively stouter G1 ultimate article ( Figs. 20H, I View FIGURE 20 , 21A, B View FIGURE 21 ) (versus G1 ultimate article relatively slenderer; Figs. 15A, B View FIGURE 15 , 17A, B View FIGURE 17 , 18H, I View FIGURE 18 , 19A, B View FIGURE 19 ).

Ecological notes. Vanni ashini inhabits shady and dry stream margins underneath stones in moist soil ( Bahir & Yeo 2007). The recent specimens were collected from drying to shallow and slow-flowing streams at relatively higher elevations (547–1170 m a.s.l.) of the southern Western Ghats.

Geographical distribution. Vanni ashini is endemic to the southernWestern Ghats of Kerala (Thiruvananthapuram district) and Tamil Nadu (Kanyakumari and Tirunelveli districts) in southern India ( Bahir & Yeo 2007; Rajesh et al. 2017; present study) ( Fig. 1B View FIGURE 1 ).

Key to the species of Vanni Bahir & Yeo, 2007 View in CoL

1. Epibranchial tooth low but discernible ( Fig. 20A, B, E View FIGURE 20 ); male pleonal somite 6 longer than telson ( Fig. 20D, G View FIGURE 20 ); male telson as long as broad, medial length ca. 1.0 × proximal width ( Fig. 20D, G View FIGURE 20 ); G1 ultimate article relatively stouter ( Figs. 20H, I View FIGURE 20 , 21A, B View FIGURE 21 )......................................................................... Vanni ashini Bahir & Yeo, 2007 View in CoL [Kerala (Thiruvananthapuram district) and Tamil Nadu (Kanyakumari and Tirunelveli districts); southern Western Ghats only]

– Epibranchial tooth indiscernible ( Figs. 14A View FIGURE 14 , 16A View FIGURE 16 , 18A, B, E View FIGURE 18 ); male pleonal somite 6 as long as telson ( Figs. 14C, E View FIGURE 14 , 16C, H View FIGURE 16 , 18D, G View FIGURE 18 ); male telson longer than broad, medial length ca. 1.1–1.3 × proximal width ( Figs. 14C, E View FIGURE 14 , 16C, H View FIGURE 16 , 18D, G View FIGURE 18 ); G1 ultimate article relatively slenderer ( Figs. 15A, B View FIGURE 15 , 17A, B View FIGURE 17 , 18H, I View FIGURE 18 , 19A, B View FIGURE 19 ).............................................. 2

2. Male pleonal somite 6 relatively narrower, elongated, proximal width ca. 1.1 × medial length ( Fig. 14C, E View FIGURE 14 ); male telson relatively more narrow, medial length ca. 1.3 × proximal width ( Fig. 14C, E View FIGURE 14 ); G1 ultimate article relatively shorter, ca. 0.2 × length of penultimate article ( Fig. 15A View FIGURE 15 ); G1 penultimate article with distal portion conspicuously narrow than basal portion, outer margin basally straight ( Fig. 15A, B View FIGURE 15 ); vulvae located clearly away from s5/s6 ( Fig. 14F View FIGURE 14 ).............................................................................................. Vanni travancorica ( Henderson, 1913) View in CoL [Kerala (Kollam and Thiruvananthapuram districts); southern Western Ghats only]

– Male pleonal somite 6 relatively broader, shorter, proximal width ca. 1.2 × medial length ( Figs. 16C, H View FIGURE 16 , 18D, G View FIGURE 18 ); male telson relatively less narrow, medial length ca. 1.1 × proximal width ( Figs. 16C, H View FIGURE 16 , 18D, G View FIGURE 18 ); G1 ultimate article relatively longer, ca. 0.3 × length of penultimate article ( Figs. 17A View FIGURE 17 , 18H View FIGURE 18 , 19A View FIGURE 19 ); G1 penultimate article with distal portion relatively less narrow than basal portion, outer margin basally concave ( Figs. 17A, B View FIGURE 17 , 18H, I View FIGURE 18 , 19A, B View FIGURE 19 ); vulvae located relatively close to s5/s6 ( Figs. 16J View FIGURE 16 , 18K View FIGURE 18 )............................................................................................... 3

3. Male pleonal somite 6 with gently concave lateral margins ( Fig. 18D, G View FIGURE 18 ); G1 relatively stouter, with relatively stouter ultimate and penultimate articles ( Figs. 18H, I View FIGURE 18 , 19A, B View FIGURE 19 )..................................... Vanni deepta Bahir & Yeo, 2007 View in CoL [Kerala (Idukki and Pathanamthitta districts); southern Western Ghats only]

– Male pleonal somite 6 with strongly concave lateral margins ( Fig. 16C, H View FIGURE 16 ); G1 relatively slenderer, with relatively slenderer ultimate and penultimate articles ( Fig. 17A, B View FIGURE 17 )............................................ Vanni gracilis sp. nov. [Kerala (Ernakulam district); southern Western Ghats only]

Genus Santanusus gen. nov.

( Figs. 22–24 View FIGURE 22 View FIGURE 23 View FIGURE 24 )

Type species. Paratelphusa (Liotelphusa) malabarica Henderson, 1912 View in CoL , by present designation; gender of genus masculine.

Diagnosis. Medium sized crabs (maximum CW 21.6 mm). Carapace relatively broad (CW/CL = ca. 1.3–1.4), relatively low ( CH /CW = ca. 0.4–0.5), with moderately convex lateral margins; frontal medial triangle incomplete, lateral margins indiscernible; postorbital cristae weakly developed posterolaterally, not reaching lateral margins of carapace; external orbital angle triangular, with short outer margin, ca. 2.5 times length of inner margin; epibranchial tooth low, located at same level of postorbital cristae; epistome posterior margin with low, broadly triangular medial tooth and gently sinuous lateral lobes ( Figs. 22A–C, E–G View FIGURE 22 , 23A View FIGURE 23 ). Maxilliped 3 with well-developed flagellum on exopod. Chelipeds relatively slender in adult males ( Figs. 22A, E View FIGURE 22 , 23A View FIGURE 23 ). Ambulatory legs relatively stout, shorter, setose ( Figs. 22A, E View FIGURE 22 , 23A View FIGURE 23 ). Male s2/s3 and s3/s4 indiscernible ( Fig. 22D, H View FIGURE 22 ). Male sternopleonal cavity relatively long, reaching to imaginary line joining bases of maxilliped 3 ( Fig. 22D, H View FIGURE 22 ). Male pleon relatively narrow, with strongly concave lateral margins; pleonal somite 6 subquadrate, relatively narrow, proximal width ca. 0.9 times medial length ( Fig. 22H View FIGURE 22 ). G1 relatively slender; ultimate article conical, relatively slender, relatively short, ca. 0.25 times length of penultimate article; penultimate article moderately stout ( Fig. 24A, B View FIGURE 24 ). G2 as long as G1, ca. 1.0 times G1 length; ultimate article relatively short, ca. 0.3 times length of penultimate article ( Fig. 24C View FIGURE 24 ). Vulvae relatively widely located from each other (VD/SW = ca. 0.2) ( Fig. 23C View FIGURE 23 ).

Etymology. The genus is named in honour of Santanu Mitra of the Crustacea Section of the Zoological Survey of India, Kolkata, for his contributions to the taxonomy of Indian freshwater crabs, in an arbitrary combination with the ending of Thelphusa Latreille, 1819 . The gender of this genus is masculine.

Remarks. Santanusus gen. nov. is differentiated from the morphologically most closely related Vanni s. str. (see Remarks for Vanni ) and herein designated Paratelphusa (Liotelphusa) malabarica described by Henderson (1912) as the type species. This new genus thus contains only one species, i.e., S. malabaricus ( Henderson, 1912) comb. nov.

Santanusus gen.nov. is distinct from other freshwater crab genera of southern India in the following morphological features: the relatively low carapace ( CH /CW = ca. 0.4–0.5) ( Fig. 22C, G View FIGURE 22 ); the weakly developed postorbital cristae, posterolaterally not reaching the carapace margin ( Figs. 22A, B, E, F View FIGURE 22 , 23A View FIGURE 23 ); the triangular external orbital angle, with outer margin short, ca. 2.5 times the inner margin length ( Figs. 22A, B, E, F View FIGURE 22 , 23A View FIGURE 23 ); the low epibranchial tooth ( Figs. 22A, B, E, F View FIGURE 22 , 23A View FIGURE 23 ); the low, broadly triangular medial tooth of the epistome posterior margin ( Fig. 22C, G View FIGURE 22 ); the well-developed flagellum on the maxilliped 3 exopod; the relatively stout and shorter ambulatory legs ( Figs. 22A, E View FIGURE 22 , 23A View FIGURE 23 ); the indiscernible male s2/s3 and s3/s4 ( Fig. 22D, H View FIGURE 22 ); the relatively long male sternopleonal cavity, reaching to the imaginary line joining the bases of the maxilliped 3 ( Fig. 22D, H View FIGURE 22 ); the relatively slender G1, with the conical and short ultimate article, ca. 0.25 times the length of the penultimate article ( Fig. 24A, B View FIGURE 24 ); the equally long G2 and G1 ( Fig. 24 View FIGURE 24 ); the relatively shorter ultimate article of the G2, ca. 0.3 times the length of the penultimate article ( Fig. 24C View FIGURE 24 ); and the relatively widely located vulvae (VD/SW = ca. 0.2) ( Fig. 23C View FIGURE 23 ).

Geographical distribution. Santanusus gen. nov. is currently known from the central and southern Western Ghats of Kerala ( Kozhikode, Palakkad, and Thrissur districts) and Tamil Nadu (Coimbatore district) of southern India ( Henderson 1912; Roux 1931; Bott 1970a, 1970b; Bahir & Yeo 2007; Klaus et al. 2014; Pati et al. 2014, 2019b; Rajesh et al. 2017; present study) ( Fig. 1B View FIGURE 1 ).