Cylindrotelphusa Alcock, 1909

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 : 1317-1322

Cylindrotelphusa Alcock, 1909

Cylindrotelphusa Alcock 1909: 380, 1910a: 259 , 1910b: 124; Colosi 1920: 11; Chace 1942:

226; Bott 1969: 360, 1970: 28; Bahir and Yeo 2007: 314; Ng et al. 2008: 67 Cylindrotelphusa – Balss 1957: 1645

Type species

Gecarcinucus (Cylindrotelphusa) steniops Alcock, 1909 , by original designation.

Diagnosis (revised from Bahir and Yeo 2007)

Carapace slightly broader than long (cw/cl = ca. 1.2–1.3), deep (ch/cl = ca. 0.7–0.9); dorsal surface strongly convex; anterolateral margin distinctly serrated; frontal margin narrow (fw/cw = ca. 0.25); postorbital cristae indistinct or well developed; external orbital angle low, indistinct or triangular, distinct, outer margin same length as inner margin; epibranchial tooth indistinct or very small, blunt; postorbital region gently to strongly concave; branchial regions highly inflated; mesogastric groove long, bifurcated posteriorly; H-shaped groove visible; frontal median triangle with dorsal margin only; epistome posterior margin with prominent, triangular median lobe ( Figures 11 (a,b) and 13(a,b); see Pillai 1951, fig. 3; Bahir and Yeo 2007, fig. 5(a,b)). Suture between male thoracic sternites s2/s3 visible as shallow depression, suture between sternites s3/s4 visible as shallow or deep, broad groove, reaching lateral margins or only visible as lateral grooves ( Figures 11 (c,g) and 13(c,g); see Bahir and Yeo 2007, fig. 5(c)). Male abdomen narrowly triangular; fifth abdominal somite distinctly broader than long; sixth abdominal somite broader than long; telson narrowly triangular, with distinctly concave lateral margins ( Figures 11 (c,h) and 13(c,h); see Bahir and Yeo 2007, fig. 5(c)). Third maxilliped exopod with well developed flagellum ( Figures 11 (i) and 13(i)). G1 long, slender or stout; terminal segment nearly straight or distinctly curved, short or very long, ca. 0.4–0.6 times length of subterminal segment ( Figures 12 (a–c) and 14(a–c); see Bahir and Yeo 2007, fig. 4(a–c)). G2 short, with short distal segment, ca. 0.2–0.3 times length of basal segment ( Figures 12 (d) and 14(d); see Bahir and Yeo 2007, fig. 4(d)).

Remarks

Cylindrotelphusa can be differentiated from other Indian gecarcinucids by the following suite of carapace and gonopod characters: carapace highly arched with a narrow front; anterolateral margin with distinct serrations; external orbital angle either low or triangular, with a very short outer margin, same length as the inner margin; frontal median triangle with dorsal margin only; third maxilliped exopod with a well developed flagellum; G2 distal segment short, ca. 0.2–0.3 times the length of the basal segment ( Figures 11 (a,b,i), 12(d), 13(a,b,i) and 14(d); see Pillai 1951, fig. 3; Bahir and Yeo 2007, figs 4(d) and 5(a,b)).

Until the present work, Cylindrotelphusa was considered to be monotypic ( Bahir and Yeo 2007; Ng et al. 2008). This is now not the case because two more species, C. breviphallus sp. nov. and C. longiphallus sp. nov., are described here. Formerly, Pillai (1951) had described a variety of Cylindrotelphusa as Gecarcinucus (Cylindrotelphusa) steniops var. granulata from North Paravur (= Parur in north Travancore) of Ernakulam district, Kerala. The first author (SKP) has tried without success to locate the types, supposedly deposited in two depositories: the Zoological Survey of India, Kolkata, and the University of Kerala (previously University of Travancore), Thiruvananthapuram. One of the present authors (VUS) tried to collect these crabs from the type locality, but without success because most of the habitat of this species (low-lying paddy fields) has now been converted into aquaculture ponds. The species might be extirpated from this area, and its extinction risk status is unclear.

The variety described by Pillai (1951) is regarded here as a valid species of Cylindrotelphusa because it possesses distinct features of the carapace, including a significant suite of characters: carapace deep (ch/cl = 0.8); anterolateral margin with distinct serrations; frontal margin narrow (fw/cw = 0.25), finely granular, nearly straight; epigastric cristae almost indistinct; postorbital cristae indistinct; external orbital angle low, indistinct; epibranchial tooth indistinct; cervical grooves extending beyond postorbital cristae up to external orbital angle; sixth male abdominal somite with straight lateral margins; male telson as long as broad; third maxilliped exopod with well developed flagellum. Therefore, Cylindrotelphusa granulata ( Pillai, 1951) comb. et stat. nov. is here recognised as a distinct species.

Currently, four species of Cylindrotelphusa are known: C. breviphallus sp. nov., C. granulata ( Pillai, 1951) , C. longiphallus sp. nov., and C. steniops ( Alcock, 1909) .

Ecological notes

Cylindrotelphusa occupies a wide array of habitats from low-lying paddy fields to hill streams. Generally, these crabs live in deep and interconnecting burrows adjacent to water bodies.

Geographic distribution

Cylindrotelphusa is endemic to the southern Indian states of Kerala and Tamil Nadu. The genus is distributed in Ernakulam, Kollam, Kozhikode, Idukki, Thiruvananthapuram and Thrissur districts of Kerala, and Nilgiris district of Tamil Nadu ( Alcock 1910b; Pillai 1951; Bott 1970; Bahir and Yeo 2007; Pati et al. 2014). It is also reported from few localities of the Western Ghats ( Bahir and Yeo 2007).

Figures

Figure 11. Cylindrotelphusa breviphallus sp. nov., holotype male (ZSI, WRC-C.1533). (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 12. Cylindrotelphusa breviphallus sp. nov., holotype male (ZSI, WRC-C.1533). (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.