Geothelphusa kumejima, Naruse & Shokita & Ng, 2006

Naruse, Tohru, Shokita, Shigemitsu & Ng, Peter K. L., 2006, A revision of the Geothelphusa leIJicerIJix species group (Crustacea: Decapoda: Brachyura: Potamidae), with descriptions of three new species, Journal of Natural History 40 (13 - 14), pp. 759-781 : 770-772

Geothelphusa kumejima new species

( Figures 6 , 9a )

Geothelphusa leυicerυix: Minei 1981, p 80, Tables 2, 3 (partim); Anonymous 1991, p 219 (partim); Anonymous 1996, p 362 (partim); Yoshigou 1999, p 20 (partim); Segawa 2000, Table 1 (partim); Kasai and Naruse 2003, p 283, Figure 67B (partim); Naruse 2005a, p 190 (partim), Plate (Crustacea: upper left); Shokita 2005b, p 56 (partim).

Material examined

Holotype: one male, CL 39.5 mm, RUMF-ZC-144, Shirase River , coll. H. Sato, 5–7 November 1994 . Paratypes: one male, CL 15.0 mm, one female, CL 36.8 mm, RUMF- ZC-146, northwest of Higa , coll. T. Naruse and H. Kasai, 11 February 2002 ; one male, CL 28.9 mm, RUMF-ZC-147, Suhara River , coll. T. Naruse, H. Kasai and her children, 11 February 2002 ; one male, CL 35.0 mm, ZRC 2006.0077 , northwestern Higa , coll. T. Naruse and H. Kasai, 11 February 2002 . Others : one male, CL 33.7 mm, four females, CL 22.5–31.7 mm, KNCC, coll. H. Sato, 18 October 1995 ; one female, CL 36.3 mm, RUMF- ZC-145, Shirase River , coll. H. Sato, 5–7 November 1994 ; two males, CL 30.0– 35.3 mm, NSMT, Suhara, coll. H. Sato, 29 December 1994 ; one female, CL 37.3 mm, KNCC, coll. H. Sato, 30 March 1994 ; two females, CL 32.0– 36.8 mm, KNCC, coll. H. Sato, 21 October 1995 ; one male, CL 40.4 mm, KNCC, branch of Shirase River , coll. H. Sato, 9 February 1997 . All specimens from Kume Island .

Description of adult

Carapace ( Figure 6a, b ) oval, convex longitudinally; surface including anterolateral region smooth, cervical groove absent, H-shaped gastric groove shallow, postorbital and epigastric cristae absent, postorbital and epigastric regions gradually raised posteriorly, shallow pit present on posterior part of external orbital angle. Front directed downwards, frontal margin medially concave or straight, not granulated; infraorbital margin cristate, granulated; supraorbital margin cristate, not granulated, L-shaped in dorsal view; external orbital angle obtuse, directed anteriorly, connected with non-granulated crista as far as anterior part of epibranchial tooth; epibranchial tooth demarcated by interruption of crista; anterolateral margin cristate, not granulated. Suborbital, subhepatic and pterygostomial regions ( Figure 9a ) smooth, sulcus not granulated or granulated on anterior part of joint with vertical groove. Cornea of eye relatively small, subdistal width of cornea as wide as base of peduncle in frontal view.

Chelae of large male asymmetric in size and shape, major chela with wide, thick, reticulated manus, long, nearly straight movable finger, narrow gap when fingers closed.

Ambulatory legs glabrous, propodi with elliptical cross-section, inner margins with no to two longitudinal rows of spines; dactyli with rectangular cross-section, inner margins with short, thin, sharp spines, outer margins with short, stout, rounded spines, outer dorsal margin of fourth ambulatory dactylus with stout, rounded subdistal spine, subequal with terminal one.

Male abdominal segments and telson triangular in general shape, telson triangular, reaching imaginary line joining proximal third of chelipedal coxae.

G1 ( Figure 6c, d ) relatively slender; subterminal segment curving outwards medially, distal margin slightly wider than proximal part, outer proximal margin uneven, knob on outer proximal angle distinct, especially in dorsal view; synovial membrane wide; terminal segment directed outwards, both inner and outer margins forming smooth lines at articulation of terminal and subterminal segments.

Variation

The epigastric and postorbital cristae may be clearer in smaller individuals (e.g. a female, KNCC, CL 22.5 mm); and the anterolateral crista, crista between the external orbital angle and epibranchial tooth, and vertical groove can be granulated; with small rows of pits on the anterolateral region (e.g. a male, RUMF-ZC-147, CL 28.9 mm).

Habitat

Geothelphusa kumejima occurs near the riverside or banks of the middle to upper reaches of the rivers, where water will seep out if the burrows are dug.

Distribution

Kume Island, Central Ryukyu Islands, Japan.

Etymology

The species name is named after the type locality, ‘‘ Kume-Jima’ ’ (5 Island), and is used as a noun in apposition .

Remarks

Several authors have referred G. kumejima to G. leυicerυix s. lato (e.g. Minei 1981). Indeed, G. kumejima can be morphologically close to G. grandioυata in the shape of carapace. However, G. kumejima can be easily differentiated from G. grandioυata by the presence of a distinct knob on the outer proximal angle of the subterminal segment of the G1 (versus indistinct in G. grandioυata).

Figures

Figure 6. Geothelphusa kumejima new species. (a) Dorsal view; (b) dorsal view of carpace; (c) ventral side of G1; (d) dorsal side of G1; (e) G2. (a) Paratype, ZRC 2006.0077, male, CL 35.0 mm; (b–e) holotype, RUMF-ZC-144, male, CL 39.5 mm. Scale bars: 10 mm (b); 5 mm (c–e).

Figure 9. Frontal view of Geothelphusa kumejima new species and Geothelphusa iheya new species. (a) Geothelphusa kumejima, paratype, ZRC 2006.0077, male, CL 35.0 mm; (b) G. iheya, paratype, ZRC 2006.0078, male, CL 28.7 mm.