Candidiopotamon rathbuni (De Man, 1914)

Shih, Hsi-Te, Naruse, Tohru & Schubart, Christoph D., 2023, Molecular evidence and differences in gonopod morphology lead to the recognition of a new species of the freshwater crab genus Candidiopotamon Bott, 1967 (Crustacea, Brachyura, Potamidae) from eastern Taiwan, ZooKeys 1179, pp. 169-196 : 169

Candidiopotamon rathbuni (De Man, 1914)

Figs 3 , 4A, B , 5A-D

Potamon (Potamon) rathbuni De Man, 1914: 128, pl. 3(4-4d) [type locality: Sun Moon [Rihyuetan], Nantou, Taiwan]; Parisi 1916: 153; Oshima 1921: 123; Balss 1922: 134; Maki and Tsuchiya 1923: 153, pl. 19(2); Balss 1937: 162, fig. 21; Sakai 1939: 580, pl. 128(1); Sakai 1940: 57; Lin 1949: 25; Chiu 1962a: 425.

Thelphusa rubra Nakagawai Nakagawa, 1915a: 1036 (nomen nudum); 1915b: 322.

Potamon (Geothelphusa) obtusipes - Terao 1915: 503, 1 unnumbered fig.; Nakagawa 1917: 303, fig. 21 (non Geothelphusa obtusipes Stimpson, 1858).

Potamon obtusipes - Nakagawa 1916: 137, pl. 2(1) (non Geothelphusa obtusipes Stimpson, 1858).

Potamon rathbuni - Koba 1936a: 166, fig. 1; Koba 1936b: 202, text-fig.; Horikawa 1940: 27; Iwata 1940: 2; Chiu 1962b: 58; Chiu 1964: 67 (part); Pretzmann 1963: 365, fig. 15.

Candidiopotamon rathbuni - Bott 1967: 210, fig. 10; Bott 1970: 189, pls 40(74), 55(75); Minei 1974: 246, figs 7-9 (part); Sakai 1976: 564, text-fig. 307; Dai et al. 1984: 115, fig. 69; Hwang and Mizue 1985: 10, fig. 7, pl. IIA (part); Shy et al. 1996: 239, fig. 17; CH Jeng et al. 1998: 70, 2 unnumbered figs; Dai 1999: 154, fig. 80, pl. 9(7) (part); Shy and Yu 1999: 94, 3 unnumbered figs, "fig. 31" on p. 106 (part); Lee and Tung 2000: 70; Ng 2000: 249 (part); Jeng et al. 2010: 80, 7 unnumbered figs; Ng et al. 2017: 76; Shy et al. 2020: 2, figs 11A, 13, 14, 16, 17 (part).

Candidiopotamon sp. - Jeng et al. 1994: 56; Jeng et al. 1996: 51; Jeng et al. 1997: 62; MS Jeng et al. 1998: 60.

Candidiopotamon guangdongense Dai, 1999: 156, fig. 81, pl. 19(8).

Candidiopotamon rathbunae - Liu and Li 2000: 90; Ng 2000: 249 (part); Chen et al. 2001: 43, 2 unnumbered figs on p. 43, 46 (part); Lee 2001: 145, 2 unnumbered figs (part); Ng et al. 2001: 49 (part); Chen et al. 2003: 29, 5 unnumbered figs (part); Naruse et al. 2004: 7, fig. 2Bd, Bv.; Shih et al. 2006: 983 (part); Ng et al. 2008: 161 (part); Shih et al. 2009: 706; Shy and Lee 2009: 207, 10 unnumbered figs (part); Chiu et al. 2015: 202, 227, 1 unnumbered fig. on p. 202 (part); Ho 2015: 141, 2 unnumbered figs (part); Liu and Hartnoll 2017: 227; Sasaki 2019: 11552 (part).

Material examined.

Taiwan - 3 males, CW 25.6 × CL 22.6-28.6 × 25.6 mm , 1 female, 38.0 × 32.8 mm, NCHUZOOL 15191, Sinsian, Wulai , New Taipei City, coll. C. A. Chen, 20 Aug. 2001 ; 1 male, 40.0 × 35.8 mm, NCHUZOOL 15189, Sinsian, Wulai , New Taipei City, coll. H.-T. Shih, 29 Apr. 1994 ; 1 male, 30.2 × 27.4 mm, 1 female, 35.1 × 30.7 mm, NCHUZOOL 12915, Jianshih, Hsinchu Co. , coll. H.-T. Shih, 25 May 2001 ; 1 female, 40.0 × 34.0 mm, NCHUZOOL 15184, Hengshan, Hsinchu Co. , coll. H.-C. Liu, 24 Sep. 1995 ; 2 males, 33.4 × 29.1-32.8 × 29.0 mm, 1 female, 33.9 × 29.0 mm, RUMF-ZC-53, Cingcyuan, Wufeng, Hsinchu Co. , coll. C.A. Chen, 28 Aug. 2001 ; 1 male, 30.9 × 27.0 mm, NCHUZOOL 15192, Shueiweiping, Dahu , Miaoli, coll. H.-D. Zhu, 7 Mar. 2001 ; 3 males, 25.7 × 22.6-35.4 × 31.2 mm, 1 female, 26.7 × 23.9 mm, NCHUZOOL 15194, Baguali, Tai-an , Miaoli, coll. H.-T. Shih, 25 Jan. 2002 ; 1 male, 34.5 × 30.6 mm, NCHUZOOL 15211, 2 males, 19.1 × 16.5, 19.8 × 17.6 mm, 5 females, 17.9 × 15.9-31.0 × 26.9 mm, NCHUZOOL 12918, 1 male, 31.6 × 27.5 mm, 1 female, 27.9 × 23.8 mm, RUMF-ZC-54, Sihjiaolin, Dongshih , Taichung, coll. H.-T. Shih, 28 Dec. 2001 ; 1 male, 23.3 × 20.3 mm, NCHUZOOL 12944, Caohu , Taichung, coll. H.-C. Liu, 23 Apr. 1993 ; 1 male, 30.4 × 26.1 mm, NCHUZOOL 12924, Taiping , Taichung, coll. students of Tunghai Univ., 8 Jun. 2001 ; 2 males, 26.4 × 23.2, 27.7 × 24.2 mm, NCHUZOOL 15214, Lianhuachih, Wucheng, Yuchih , Nantou, coll. H.-T. Shih, 22 Jun. 2001 ; 1 male, 28.0 × 23.9, 1 female, 29.7 × 25.4 mm, NCHUZOOL 15181, Rihyuetan , Nantou (type locality), coll. H.-T. Shih and H.-T. Hung, 4 Mar. 2003 ; 1 male, 38.6 × 32.4 mm, NCHUZOOL 15187, Sinshan, Shueili , Nantou, coll. H.-C. Liu, 8 Aug. 1995 ; 1 male, 36.3 × 30.9, 1 female, 24.2 × 21.0 mm, NCHUZOOL 15185, Jiji, Shueili , Nantou, coll. H.-C. Liu, 8 Aug. 1995 ; 3 males, 32.3 × 27.6-36.7 × 31.1 mm, 2 females, 26.4 × 22.5, 33.0 × 28.7 mm, NCHUZOOL 15205, Chukou, Fanlu, Chiayi Co. , coll. H.-C. Liu, 21-22 Mar. 1996 ; 1 male, 44.6 × 36.8 mm, 1 female, 40.9 × 34.4 mm, RUMF-ZC-86, Guanyin Waterfall, Chiayi Co. , coll. J.-Y. Shy, 6 Dec. 1990 ; 1 male, 35.2 × 29.3 mm, NCHUZOOL 12946, Alishan, Chiayi Co. , coll. C.-H. Wang, 26 May 2002 ; 1 male, 21.2 × 19.1 mm, NCHUZOOL 15182, Dakeng, Dongyuan, Dongshan , Tainan, coll. H.-T. Shih, 20 Oct. 2000 ; 5 males, 19.7 × 16.8-29.6 × 25.6 mm, 1 female, 24.9 × 20.9 mm, NCHUZOOL 15186, Gaoyuan, Dongshan , Tainan, coll. H.-C. Liu, 16 Aug. 1997 ; 1 male, 26.6 × 22.6 mm, NCHUZOOL 15196, Gueidan, Nansi , Tainan, coll. H.-T. Shih, 20 Oct. 2000 ; 1 male, 28.8 × 24.9 mm, NCHUZOOL 15198, Mincyuan, Sanmin , Kaohsiung, coll. C.-B. Wu, 17 Aug. 2000 ; 1 male, 30.6 × 26.0 mm, 1 female, 25.0 × 21.8 mm, NCHUZOOL 15195, Baolai, Liouguei , Kaohsiung, coll. H.-T. Shih, 14 Dec. 2001 ; 1 male, 31.5 × 26.6 mm, NCHUZOOL 12922, Chuyunshan , Taoyuan, Kaohsiung, coll. C.-S. Chen, 6 May 2000 ; 1 male, 34.3 × 29.0 mm, NCHUZOOL 15188, Guanglin, Meinong , Kaohsiung, coll. C.-S. Chen, 15 Dec. 2000 ; 3 females, 33.7 × 29.7-40.4 × 35.0 mm, NCHUZOOL 15183, Guanglin, Meinong , Kaohsiung, coll. H.-C. Liu, 4 Aug. 1995 ; 1 male, 37.3 × 32.3 mm, 1 female, 26.7 × 23.2 mm, NCHUZOOL 15190, Jiasian , Kaohsiung, coll. H.-C. Liu, 5 Aug. 1995 ; 3 males, 30.5 × 26.2-38.8 × 34.0 mm, 1 female, 27.8 × 23.8 mm, NCHUZOOL 15197, Tianliao , Kaohsiung, coll. H.-T. Shih, 16 Nov. 2001 ; 1 male, 24.2 × 20.5 mm, 1 female, 26.2 × 22.3 mm, NCHUZOOL 15202, Shandimen , Pingtung, coll. H.-C. Liu, 16 Aug. 1997 ; 1 male, 34.4 × 29.4 mm, NCHUZOOL 15201, Haocha , Pingtung, coll. H.-T. Shih, 31 May 2000 ; 2 males, 36.3 × 30.7, 37.7 × 32.3 mm, 1 female, 32.9 × 27.3 mm, NCHUZOOL 15199, Taiwu , Pingtung, coll. C.-C. Huang and C.-K. Yang, 29 Jul. 1999 ; 1 male, 34.5 × 29.0 mm, 1 female, 37.4 × 30.9 mm, RUMF-ZC-55, Taiwu , Pingtung, coll. H.-T. Shih, 12 Nov. 2000 ; 2 males, 33.4 × 28.3, 37.5 × 31.7 mm, NCHUZOOL 15203, Wutan, Taiwu , Pingtung, coll. H.-C. Liu, 18 Jul. 1997 ; 3 females, 13.2 × 11.3-29.5 × 24.9 mm, NCHUZOOL 12925, Laiyi , Pingtung, coll. H.-C. Liu, 16 Jul. 1996 .

Diagnosis.

Carapace subtrapezoidal, CW 1.10-1.21 × CL (mean 1.16, n = 5), dorsal surface almost flat, relatively rough, epigastric and postfrontal cristae distinct, both cristae represented by 1-3 oblique lines of granules, lateral end of postfrontal cristae far apart from epibranchial tooth; external orbital and epibranchial teeth distinct, sharp, directed anteriorly. G1 terminal segment proportionally longer, more slender, distal opening directed laterally, distal inner edge with keel-like projection in dorsal view, projection proportionally small, directed more laterally; G1 subterminal segment straight.

Description.

Carapace (Figs 3A, B , 4A ) subtrapezoidal in dorsal view, CW 1.10-1.21 × CL (mean 1.16, n = 5), dorsal surface almost flat, relatively rough, somewhat pilose. Epigastric cristae distinct; postorbital crista, represented by 1-3 oblique lines of granules, not reaching epibranchial tooth. External orbital angle acute, directed anteriorly; ridge between external orbital angle and distinct epibranchial tooth cristate and granulated; anterolateral margin distinctly cristate, lined with large, elongated granules.

Antenna (Fig. 3B ) short, reaching ~ 1/2 length of basal segment of antenna when antenna folded backwards.

Eye (Fig. 3B ) developed; maximal width of cornea wider than base of peduncle in frontal view.

Chelae of large males unequal, females or young specimens with subequal chelae; palm of major chela (Fig. 3C ) ~ 2/3 ×as high as minor chela, outer surface with scattered granules; cutting edges of both fingers with regularly arranged large and small teeth, gape almost absent when fingers closed.

Ambulatory legs moderately long; propodus cross-section oblong, each of 2 inner and 1 ventral outer longitudinal margins with 1 spine-row.

Male pleonal somites elongate trapezoidal, sixth pleonal somite length ~ 1/2 of its width; telson obtusely triangular, length ~ 1/2 of its width, distal end reaching imaginary line joining lower hinges of cheliped coxae. Female pleon of adult wide, covering ventral surface of thoracic sternum except for part of thoracic sternites 1 and 2.

G1 (Fig. 3D, F ) straight in dorsal view when dorso-proximal margin of subterminal segment set parallel to observer’s eyes. Ventral side of subterminal segment with median seam extending to subproximal part of terminal segment. Synovial membrane long, wide, occupying distal ~ 2/5 of subterminal segment in dorsal view. Terminal segment bottle-necked, relative width gradually narrowed from northwestern (Fig. 3F1 ) to southwestern populations (Fig. 3F3 ), but no clear gap between them (Fig. 3F ); distal opening directed outwards, with relatively small, laterally directed keel-like projection on opposite side of opening. G2 slightly shorter than G1; G2 flagellum ~ 1/4 length of G2 total length.

Vulvae close to each other, obliquely oblong, occupying proximal two-thirds of thoracic sternite 6.

Coloration

(Figs 4A, B , 5A-D ). Most large specimens are dark red, but sometimes dark purple or orange individuals can be found. Small individuals are generally dark brown with black spots.

Distribution

(Fig. 1 ). Candidiopotamon rathbuni is distributed along the western side of the Central Range, i.e., New Taipei City, Taoyuan, Hsinchu Co., Miaoli, Taichung, Changhua, Yunlin, Chiayi Co., Tainan, Kaohsiung, and the northwestern part of Pingtung. The type locality of C. rathbuni is Rihyuetan (= Sun Moon Lake, or the Candidius Sea), Nantou, west of the Central Range of Taiwan.

Habitat.

Most large specimens were found under large stones within streams. Sometimes adults move outside the water at night.

Remarks.

Based on one male (31.4 × 26 mm) and one female (37 × 31.3 mm) specimens, De Man (1914) described the morphology of Candidiopotamon rathbuni in great detail except for the gonopods. The lack of a description of G1 makes it difficult to ascertain which species is the real C. rathbuni . The topotypic specimens of C. rathbuni (NCHUZOOL 15187, 15185, 15214) possess the laterally directed subdistal keel and straight subterminal segment of G1. Furthermore, the type locality of C. rathbuni , Sun Moon Lake (= Rihyuetan), is located in west-central Taiwan (i.e., west of the Central Range, <1000 m, a.s.l), which suggests that the species distributed in western Taiwan keeps the name C. rathbuni , and that of eastern Taiwan is herewith described as a new species.

In his papers on the life history of Paragonimus westermani , Nakagawa (1915a, 1915b) used " Thelphusa rubra Nakagawai " for the specimens collected by himself from Hsinchu (including Miaoli), northwestern Taiwan as the second intermediate host of the species, without further information on the specimens he observed. We have examined the specimens from Hsinchu (NCHUZOOL 12915, 15184, RUMF-ZC-53) and Miaoli (NCHUZOOL 15192, 15194), which belong to C. rathbuni from western Taiwan in morphology and genetics. Regarding the brick-red coloration from the name “rubra”, the coloration of C. rathbuni is variable from dark purple and dark red to orange (see “Coloration” of this species).

Subsequently, Terao (1915) referred Nakagawa’s specimens of " Thelphusa rubra Nakagawai " to Potamon (Geothelphusa) obtusipes (Stimpson, 1858). However, the real P. obtusipes is only distributed in Amami Islands, the Ryukyus and does not show the red coloration ( Shih 2008: figs 51, 52). Terao’s (1915: 508) drawing of P. (G.) obtusipes clearly showed that his specimen represented a species of Candidiopotamon , and Ng et al. (2001) also doubted that " Thelphusa rubra Nakagawai " was actually C. rathbuni . In addition to the above history, Nakagawa stated that "As a matter of convenience, the crab, which has been described as Thelphusa sp., is provisory treated here (as Thelphusa rubra Nakagawai) temporarily". Because Nakagawa collected the specimens from Hsinchu and Miaoli, northwestern Taiwan where C. rathbuni is distributed, " Thelphusa rubra Nakagawai " sensu Nakagawa (1915a, 1915b) and Potamon (Geothelphusa) obtusipes sensu Terao (1915) are considered here as junior synonyms of C. rathbuni .

Figures

Figure 1. Collection sites for Candidiopotamon rathbuni (De Man, 1914) (circles) and Candidiopotamon penglai sp. nov. (squares) in Taiwan, as well as other congeners from the Ryukyus, Japan. Different colors indicate sampling sites of clades. Dotted lines indicate the possible biogeographic boundaries between clades NW, W, SW, S, SE, E 1, and E 2, corresponding to the color in Fig. 2; as well as species. The red star and blue star indicate the type localities of C. rathbuni and C. penglai sp. nov., respectively. Three forms of male left G 1 are shown for clades in C. rathbuni and two forms for clades in C. penglai sp. nov.

Figure 3. Candidiopotamon rathbuni (De Man, 1914): male (44.6 x 36.8 mm) from Chiayi, western Taiwan (RUMF-ZC- 86) (A - E); male (35.4 x 31.2 mm) from Miaoli, northwestern Taiwan (NCHUZOOL 15194) (F 1); male (36.7 x 31.1 mm) from Chiayi, western Taiwan (NCHUZOOL 15205) (F 2); male (36.3 x 30.7 mm) from Taiwu, Pingtung, southwestern Taiwan (NCHUZOOL 15199) (F 3). A carapace, dorsal view B carapace, frontal view C male major chela, outer view D 1 left G 1, ventral view D 2 left G 1, dorsal view D 3 left G 1 terminal segment, dorsal view E left G 2 F 1 - 3 left G 1 s terminal segment, dorsal view. Scale bars: 10 mm (A - C); 2 mm (D - F). Arrow indicates the keel-like projection on the distal inner edge of the terminal segment.

Figure 4. Color in life of Candidiopotamon rathbuni (De Man, 1914) (A, B) and Candidiopotamon penglai sp. nov. (C-F). A, C, E overall dorsal view B, D, F overall ventral view A, B NCHUZOOL 15181 (male, 28.0 x 23.9 mm, Rihyuetan, Nantou, western Taiwan) C, D NCHUZOOL 15204 (male, 39.7 x 34.4 mm, Nanrenshan, Pingtung, southern Taiwan); NCHUZOOL 15224 (paratype male, 36.4 x 30.9 mm, Liyu Lake, Shoufeng, Hualien, eastern Taiwan).

Figure 5. Color in life of Candidiopotamon rathbuni (De Man, 1914) (A-D) and Candidiopotamon penglai sp. nov. (E-H). A, B NCHUZOOL 15194 (male, 35.4 x 31. 2 mm, Tai-an, Miaoli, northwestern Taiwan) C NCHUZOOL 15211 (male, 24.8 x 22.1 mm, Dongshih, Taichung, western Taiwan) D NCHUZOOL 15181 (male, 28.0 x 23.9 mm, Rihyuetan, Nantou, western Taiwan) E, F NCHUZOOL 15204 (2 males, 39.7 x 34.4 mm, 40.6 x 34.3 mm, Nanrenshan, Pingtung, southern Taiwan) G NCHUZOOL 15224 (paratype male, 36.4 x 30.9 mm, Liyu Lake, Shoufeng, Hualien, eastern Taiwan) H NCHUZOOL 15229 (male, 33.1 x 29.7 mm, Jili Lake, Guangfu, Hualien, eastern Taiwan).