Geothelphusa iheya, 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 : 772-775

Geothelphusa iheya new species

( Figures 7 , 9b )

Geothelphusa sp. 1: Shokita 2002, p 167.

Geothelphusa leυicerυix: Naruse 2005a, p 190 (partim); Shokita 2005b, p 56 (partim).

Material examined

Holotype: one male, CL 32.6 mm, RUMF-ZC-148, promenade of Mt Koshi-Dake , coll. H. Sato, 1 June 2001 . Paratypes: one male, CL 32.2 mm, RUMF-ZC-149, data same as holotype; two males, CL 25.8–28.9 mm, ZRC 2006.0078 , southeastern side of Mt Gayou- Zan , coll. T. Naruse, 30 April 2001 ; one male, CL 32.4 mm, NSMT, downstream of Kamiya River , coll. S. Chiba, 12 November 2000 ; one male, CL 18.9 mm, six females, CL 6.7–34.6 mm, RUMF-ZC-150, upper reach of dam reserve, northern side of Mt Asa-Dake , coll. T. Naruse, 29 April 2001 ; three males, CL 8.7–15.9 mm, RUMF-ZC-151, west side of Mt Gayou-Zan , coll. T. Naruse, 30 April 2001 ; two males, CL 8.7–32.6 mm, three females, CL 9.1–23.2 mm, RUMF-ZC-152, southeastern side of Mt Gayou-Zan , coll. T. Naruse, 30 April 2001 ; one male, CL 11.3 mm, two females, CL 8.91–23.9 mm, RUMF- ZC-153, dam reserve, south of Gakiya , coll. T. Naruse, 30 April 2001 . Others : six males, CL 24.4–32.3 mm, one female, CL 26.8 mm, KNCC, Dana, coll. H. Sato, 3 June 2001 ; one female, CL 24.2 mm, KNCC, Mt Koshi-Dake , coll. H. Sato, 10 December 2001 ; two males, CL 19.7–26.6 mm, two females, CL 30.6–30.8 mm, KNCC, Dana, coll. H. Sato, 11 December 2001 . All specimens from Iheya Island .

Description of adult

Carapace ( Figure 7a, b ) oval, convex longitudinally, surface smooth; anterolateral region with rows of pits or low granules directed obliquely outwards, appears rugose, cervical groove absent, H-shaped gastric groove distinct, postorbital and epigastric cristae very low, without pit behind external orbital angle. Front directed downwards, frontal margin straight, cristate, not granulated; orbital margins cristate, infraorbital and outer part of supraorbital margins granulated, supraorbital margin L-shaped in dorsal view; epibranchial tooth demarcated by a granule on anterolateral margin, low granulated crista between epibranchial tooth and external orbital angle, but not connected to both structures in most individuals; anterolateral margin distinctly cristate on anterior two-fifths of carapace, granulated. Suborbital, subhepatic, and pterygostomial regions ( Figure 9b ) smooth, vertical groove and anterior part of epimeral sulcus granulated. Antennule reaching inner third of antennal basis when antennule opened outwards. Antenna reaching proximal half of antennal basis when antennule folded inwards. Eye with cornea relatively small, subdistal width of cornea as wide as base of peduncle in frontal view.

Chelae of large male asymmetrical in size and shape, major chela with wide, thick, and reticulated manus, long movable finger.

Ambulatory legs with very short setae, almost glabrous; propodus with elliptical crosssection, with two and one longitudinal rows of spines on inner and outer ventral margins, respectively; dactylus with rectangular cross-section, four longitudinal margins, each margin with thin, sharp spines, distal spines strong, subdistal spine of outer dorsal margin of fourth ambulatory leg thin, sharp, smaller than terminal spine, on outer margin.

Male abdominal segments and telson triangular, telson distinctly bell-shaped; telson reaching imaginary line joining posterior two-fifths of chelipedal coxae.

G1 ( Figure 7c, d ) stout; subterminal segment nearly straight, but slightly curved outwards on proximal three-quarters, outer proximal angle without knob; synovial membrane wide; terminal segment directed outwards, inner margin slightly concave, terminal segment strongly directed outwards.

Variation

In some specimens, the frontal and anterolateral regions may be rugose; there is no pit behind the eye; the anterior half of the subhepatic region can have numerous clumps of granules; there is no granule on the outer half of the supraorbital margin; the outer to upper surfaces of the cheliped manus and carpus can be granulated; and the outer and inner surfaces of the cheliped merus are rugose (e.g. a male, KNCC, CL 19.7 mm; a female, RUMF-ZC-150, CL 21.0 mm).

Habitat

Geothelphusa iheya has been found along the sides of rivers, on the banks, or within the water of the middle to upper reaches. The species, however, seems to prefer slow-flowing streams.

Disribution

Iheya Island, the Central Ryukyu Islands, Japan.

Etymology

The species name is named after the type locality, ‘‘Iheya Island’’, and is used as a noun in apposition.

Remarks

Geothelphusa iheya n. sp. is morphologically closest to G. miyakoensis Shokita, Naruse, and Fujii, 2002 , in the granulated anterolateral margin of the carapace. However, G. iheya can easily be differentiated from G. miyakoensis by the shape of the G1 (stout in G. iheya versus relatively slender in G. miyakoensis ) and the degree of bending of the terminal segment of the G1 (strongly directed outwards versus gently directed outwards).

Figures

Figure 7. Geothelphusa iheya 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 2006.0078, male, CL 28.7 mm; (b–e) holotype, RUMF-ZC-148, male, CL 32.6 mm. Scale bars: 10 mm (b); 1 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.