Geothelphusa, Stimpson, 1858

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 : 761-765

Geothelphusa leIJicerIJix ( Rathbun, 1898)

( Figures 2 , 3 , 8a )

Potamon (Geothelphusa) leυicerυix: Rathbun 1898, p 28, Plate 2(5–8); de Man 1899, p 140; Rathbun 1905, p 223, Plate 18(12); Sakai 1940, p 57.

Geothelphusa dehaani: Stimpson 1858, p 101 ; Stimpson 1907, p 112, Plate 17(2); Balss 1922, p 135.

Thelphusa Dehaanii : A. Milne Edwards 1869, p 174 (partim).

Potamon (Geothelphusa) dehaani: Ortmann 1897, p 313 (partim).

Potamon (Potamonautes) dehaani: Rathbun 1905, p 204 (partim); Shen 1932, p 89 (partim).

Geothelphusa dehaani dehaani: Bott 1967, p 211 (partim).

Geothelphusa leυicerυix: Bott 1970, p 155, Plate 58(93, 94) (partim); Minei 1973, p 212 (partim); Sakai 1976, p 558 (English text), 346 (Japanese text) (partim); Minei 1981, p 80, Tables 2, 3 (partim); Miyake 1983, p 244; Shokita 1990, Table 2 (partim); Anonymous 1991, p 219 (partim); Suzuki and Tsuda 1994, p 318; Shy et al. 1994, p 784 (partim); Anonymous 1996, p 362 (partim); Yoshigou 1999, p 20 (partim); Suzuki and Okano 2000, p 30; Segawa 2000, Table 1; Shokita 2002, p 167; Shokita et al. 2002, p 446 (partim); Kasai and Naruse 2003, p 283 (partim); Naruse 2005a, p 190 (partim); Shokita 2005b, p 56 (partim).

Geothelphusa sp. (5 G. miyakoensis ): Segawa 2000, p 243, Table 1, Figures 1 , 2 (partim).

Non Potamon (Geothelphusa) leυicerυix: Miyake and Minei 1965, p 377.

Non Geothelphusa leυicerυix: Minei 1968, p 99, Figure 11; Gima and Shokita 1980, p 9, Figures 7 , 8 ; Miyake 1983, p 244, Plate 51; Ng and Shokita 1995, p 3; Shokita 1996, p 348, Photograph 1.

Material examined

Holotype: one male, CL 48.3 mm, USNM 20642 , Loo Choo Islands (probably Tokashiki ), coll. F. Sakamoto. Others: one male, CL 35.3 mm, one female, CL 38.3 mm, ZRC 2006.0074 , upstream to headwater of Tokashiki River , coll. H. Sato, 8 July 2001; one male, CL 37.9 mm, RUMF-ZC-137, a stream on the southeastern side of a mountain located between Tokashiki and Tokashiku, coll. T. Naruse and T. Kamijo , 20 November 2000; one male, CL 42.0 mm, one female, CL 40.3 mm, KNCC, headwater of Tokashiki River , coll. H. Sato, 22 May 2001; one male, CL 12.5 mm, RUMF-ZC-138, locality same as RUMF-ZC-137, coll. T. Naruse , 25 April 1999; one male, CL 13.5 mm, RUMF-ZC- 139, a stream located on the south of Mt Akama , coll. T. Naruse and T. Kamijo , 20 November 2000. All specimens from Tokashiki Island.

Description of adult

Carapace ( Figures 2a , 3a, b ) oval, swollen longitudinally and transversely; surface including anterolateral region smooth, cervical groove shallow, H-shaped gastric groove distinct, postorbital and epigastric cristae absent, postorbital and epigastric regions posteriorly raised, deep pit on posterior part of external orbital angle in some large individuals. Front directed downwards, frontal margin straight, cristate, not granulated; infraorbital margin cristate, granulated on outer third; supraorbital margin cristate, not granulated, L-shaped in dorsal view; external orbital angle obtuse, directed anteriorly; epibranchial tooth demarcated by interrupted crista; very low crista present between external orbital angle and epibranchial tooth, this crista confluent or interrupted with tooth and angle; anterolateral margin cristate, not granulated. Suborbital, subhepatic, and pterygostomial regions ( Figures 2b , 8a ) smooth, epimeral sulcus granulated on anterior part of joint of epimeral sulcus and vertical groove. Eye with relatively small cornea, subdistal width of cornea as wide as base of peduncle in frontal view.

Chelae of large male ( Figures 2a , 3a ) asymmetrical in size and shape, relatively smooth, major chela with wide, thick, and reticulated manus, long movable finger directed inwards, immovable finger directed ventrally, forming narrow gape when chela closed.

Ambulatory legs glabrous, propodi with elliptical cross-section, one or no and one or two longitudinal rows of spines on outer and inner margins, respectively; dactyli with rectangular cross-section with four longitudinal margins, each margin lined with short, stout, abraded spines, distal spines strong, subdistal spine of outer dorsal margin of fourth ambulatory dactylus stout, rounded, smaller than terminal spine on outer dorsal margin.

Male abdominal segments and telson triangular, telson triangular, reaching imaginary line joining posterior third of chelipedal coxae.

G1 ( Figures 2c, d , 3 c–f) very slender, tapering distally, subterminal segment curving outwards medially, with low knob on outer proximal angle; synovial membrane slender; terminal segment directed outwards, proximal part as wide as distal margin of subterminal segment.

Variation

The anterolateral margin of the carapace may be weakly granulated and the cervical groove occasionally undiscernible in some specimens. The outer surface of the chela of smaller specimens is usually rougher (more rugose) than in adults, with the upper region of the carpus granulated.

Colour

Geothelphusa leυicerυix is khaki in colour on the dorsal surfaces when alive. Habitat

Geothelphusa leυicerυix was caught from very small streams less than a metre in width and about 5 cm in depth. They were seen in the streams themselves or along the banks.

Distribution

Tokashiki Island, Kerama Group, Central Ryukyu Islands, Japan.

Remarks

The holotype of G. leυicerυix was collected by a Japanese collector, Mr F. Sakamoto from ‘‘Loo Choo Island’’ (present-day Ryukyus) ( Rathbun 1898, p 27; 1905, p 223). It is uncertain where exactly Mr Sakamoto collected the holotype as there was no other information. Although the species has since been reported from various parts of the Ryukyus by Japanese workers (e.g. Sakai 1976; Minei 1981; Shokita et al. 2002; Kasai and Naruse 2003), the holotype has not been directly compared with the recent material. Our study shows that what is presently called G. leυicerυix is actually a mix of four species, three of which are new. The holotype of Geothelphusa leυicerυix agrees well with the specimens from Tokashiki, notably in the form of their slender and gently tapered G1s ( Figures 2c, d , 3c, d, f ). Thus, we believe the type locality of G. leυicerυix is actually Tokashiki, Kerama Group, Central Ryukyu Islands, Japan. The specimens from three islands, Okinawa, Kume and Iheya, are all distinct from G. leυicerυix s. str. as well as from each other, and are here recognized as different species (see below).

One of the medium-sized specimens of G. leυicerυix collected from Tokashiki Island (ZRC 2006.0074, CL 35.3 mm) shows variation in the form of the G1. The left G1 is sinuous ( Figure 3e ), but the right G1 is more slender and gently curving outwards ( Figure 3f ), the typical shape of G1 for the species. The G1s of the other male specimens all agree with the right G1 of this specimen. As such, the unusual form of the left sinuous G1 is almost certainly the result of aberrant regrowth after injury and/or damage.

Stimpson (1858, 1907) recorded G. dehaani on the basis of the material collected from the Amakirrima Islands (5Kerama Group) (near Loo Choo) by an officer of the steamer ‘‘John Hancock’’ [ Stimpson 1907, p 113; see also Habersham (1857) and Vasile et al. (2005)] and this record has been followed by subsequent authors (A. Milne Edwards 1869; Ortmann 1897; Rathbun 1905; Balss 1922; Shen 1932; Bott 1967). The drawing of this specimen [ Stimpson 1907, p 112, Plate 17(2)], however, shows a narrow front and no trace of a postorbital crista. Furthermore, the major chela is very large in relation to the body size. These are not the features of G. dehaani s. str. As Minei (1973) and Sakai (1976) have discussed, there is no doubt that Stimpson’s (1858) specimen is not G. dehaani but G. leυicerυix.

Up to the present, four islands of the Central Ryukyu Islands have been listed as the range of G. leυicerυix, namely Tokashiki ( Minei 1973), Okinawa ( Minei 1973), Kume ( Minei 1981), and Amami-Ohshima ( Sakai 1976). The specimens from Tokashiki (the actual type locality of G. leυicerυix) are clearly different from those from Okinawa and Kume, and both are regarded as undescribed species (see below). Sakai’s (1976, p 581, Plate 198, Figure 2 ) drawing of G. leυicerυix from Amami-Ohshima shows a distinct postorbital crista and wider carapace front. Judging from his drawing, his material from Amami-Ohshima is clearly G. sakamotoana , not G. leυicerυix. Specimens we have on hand from Kume which are superficially similar to G. leυicerυix are also here referred to as a new species (see below).

Figures

Figure 1. Map of the Okinawa Group in East Asia.

Figure 2. Geothelphusa leυicerυix (Rathbun, 1905), holotype, USNM 20642, male, CL 48.3 mm. (a) Dorsal view; (b) frontal view of carapace; (c) ventral side of left G1; (d) dorsal side of left G1. Scale bars: 10 mm (b); 5 mm (c, d).

Figure 3. Geothelphusa leυicerυix (Rathbun, 1905). (a) Dorsal view; (b) dorsal view of carapace; (c, e) ventral side of left G1; (d) dorsal side of left G1; (f) ventral side of right G1. (a, e, f) ZRC 2006.0074, male, CL 35.5 mm; (b– d) RUMF-ZC-137, male, CL 37.9 mm. Scale bars: 10 mm (b); 5 mm (c–f).

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 8. Frontal view of Geothelphusa leυicerυix (Rathbun, 1898) and G. grandioυata new species. (a) Geothelphusa leυicerυix, ZRC 2006.0074, male, CL 35.3 mm; (b) G. grandioυata, paratype, ZRC 2006.0076, male, CL 44.8 mm.