Metaplax elegans De Man, 1888

Shih, Hsi-Te, Hsu, Jhih-Wei, Wong, Kingsley J. H. & Ng, Ngan Kee, 2019, Review of the mudflat varunid crab genus Metaplax (Crustacea, Brachyura, Varunidae) from East Asia and northern Vietnam, ZooKeys 877, pp. 1-29 : 1

Metaplax elegans De Man, 1888 Figures 2 A–C , 3 , 7 A–D

Metaplax elegans De Man, 1888: 164, pl. 11(4-6) (type locality: Mergui, Myanmar); Alcock 1900: 434 (East India: Godavari Delta; Myanmar: Mergui); Gordon 1931: 528 (Hong Kong); Rathbun 1931: 100 (China: Fujian; Guangdong); Tweedie 1936: 69 (Malaysia: Selangor; Singapore); Shen 1940a: 74, 95 (China: Zhejiang; Fujian); Shen 1940b: 236 (Hong Kong); Tweedie 1950: 353 (Malaysia: Labuan; Kuching); Macnae 1963: 104, 180 (list); Dai et al. 1986: 509, fig. 289 (1-2), pl. 72(5) (China: Guangdong); Fukui et al. 1989: 230, fig. 25 (W Taiwan); Dai and Yang 1991: 557, fig. 289 (1-2), pl. 72(5) (China: Guangdong); J.-T. Shih et al. 1991: 126 (Taiwan: New Taipei City); Davie 1992: 352, pl. 2B (Hong Kong); Choy and Booth 1994: 243 (Brunei); Huang 1994: 598 (list; China); Tan and Ng 1994: 82 (Singapore; Malaysia); Kuo 1995: 31, 82, 97, 191, 4 unnumbered figs (W Taiwan); Wang and Liu 1996a: 128, figs 171-172 (W Taiwan); Wang and Liu 1996b: 103-104, 2 unnumbered figs (W Taiwan); Fransen et al. 1997: 125 (syntype; Mergui, Myanmar); Ho and Hung 1997: 108-109, 1 unnumbered fig.; Kosuge et al. 1997: 182 (Vietnam: Haiphong); Jeng et al. 1998: 68, 3 unnumbered figs (Taiwan: Taichung); Wang and Liu 1998a: 128, figs 171-172 (W Taiwan); Wang and Liu 1998b: 142, 2 unnumbered figs (W Taiwan); Lee and Leung 1999: 68, pl. 11 (Hong Kong); Ng and Sivasothi 1999: 73, 2 unnumbered figs (Singapore); Jeng and Wang 2000: 38, 2 unnumbered figs (Taiwan: Taichung); Lee and Tung 2000: 70 (list); Dev Roy and Bhadra 2011: 36 (list; E India); Lee 2001: 114, 3 unnumbered figs (W Taiwan); Ng et al. 2001: 45 (list; Taiwan); Kitaura et al. 2002: 684 (Vietnam: Haiphong); Ng and Davie 2002: 379 (Thailand: Phuket); Wang and Liu 2003: 128, figs 171-172 (W Taiwan); Naiyanetr 2007: 112 (list: Gulf of Thailand); Dev Roy 2008: 135 (list; India); Huang 2008: 668 (list; China); Ng et al. 2008: 226 (list); Yang et al. 2008: 803 (list; East and South China seas); Rath and Dev Roy 2008: 72, pl. 4(5) (NE India); Liu and Wang 2010: 72, 3 unnumbered figs (W Taiwan); Lee et al. 2013: 108, 2 unnumbered figs (Taiwan: Tainan); Ng et al. 2017: 110 (list; Taiwan).

Materials examined.

Taiwan: 8 ♂♂ (6.1-14.0 mm), 4 ♀♀ (8.0-13.2 mm) (NCHUZOOL 15479), Danshuei River mangroves, New Taipei City, coll. P.-Y. Hsu and J.-W. Hsu, 24 Mar. 2017; 4 ♂♂ (11.8-15.9 mm), 4 ♀♀ (14.1-15.3 mm) (NCHUZOOL 15480), Jhuwei, New Taipei City, 4 Oct. 1995; 1 ♂ (12.1 mm) (NCHUZOOL 15481), Sinfeng, Hsinchu, 15 Jan. 2014; 2 ♂♂ (8.4-10.5 mm), 5 ♀♀ (6.3-12.1 mm) (NCHUZOOL 15482), Siangshan, Hsinchu, 11 Aug. 2008; 1 ♂ (13.2 mm), 5 ♀♀ (8.7-9.7 mm) (NCHUZOOL 15483), Siangshan, Hsinchu, 13 Mar. 2008; 4 ♂♂ (10.1-11.3 mm), 1 ♀ (11.7 mm) (NCHUZOOL 15484), Haishangu, Hsinchu, 27 Aug. 2013; 1 ♂ (10.8 mm), 3 ♀♀ (8.8-11.6 mm) (NCHUZOOL 15485), Wufu Bridge, Miaoli, 2 Dec. 2015; 4 ♂♂ (12.0-15.1 mm) (NCHUZOOL 15486), Fangyuan, Changhua, 2014; 4 ♂♂ (10.0-12.2 mm), 6 ♀♀ (8.1-12.1 mm) (NCHUZOOL 15487), Yuliao R. estuary, Changhua, coll. J.-W. Hsu et al., 16 Jan. 2017; 4 ♂♂ (5.3-10.6 mm), 3 ♀♀ (10.2-12.9 mm) (NCHUZOOL 15488), area between Yunlin and Chiayi, coll. K.-C. Li and C.-T. Wang, 25 Aug. 2003; 1 ♂ (12.7 mm) (NCHUZOOL 15496), Dongshih, Chiayi County, coll. P.-Y. Hsu, 24 Jan. 2017; 4 ♂♂ (11.5-13.1 mm), 3 ♀♀ (6.7-10.7 mm) (NCHUZOOL 15489), Cihhu, Kinmen, coll. H.-T. Shih and P.-Y. Hsu, 29 June 2018. China: 3 ♀♀ (14.0-16.8 mm) (NCHUZOOL 15495), Dongzhai Harbor, Hainan, 23 June 2004; 3 ♀♀ (13.9-16.6 mm) (NCHUZOOL 15457), Dongzhai Harbor, Hainan, 23 June 2004. Vietnam: Ho Chi Minh: 8 ♂♂ (5.8-16.5 mm), 9 ♀♀ (6.5-13.7 mm) (NCHUZOOL 15490), Rung Sac, Long Hoa, 12 Oct. 2017; 1 ♂ (18.2 mm), 1 ♀ (12.7 mm) (NCHUZOOL 15491), TT. Can Thanh mangroves, Can Gio, 13 Oct. 2017; 5 ♂♂ (16.0-17.6 mm) (NCHUZOOL 15499), TT. Can Thanh mangroves, Can Gio, 13 Oct. 2017. Malaysia: 7 ♂♂ (7.7-12.6 mm), 14 ♀♀ (8.9-12.0 mm) (NCHUZOOL 15492), Mersing, Johor, 19 July 2010. Singapore: 1 specimen (not examined, only for DNA study; ZRC 1997.683), Sungei Buloh, 1996; 2 ♂♂ (9.4-11.0 mm), 1 ♀ (6.4 mm) (NCHUZOOL 15493), Lim Chu Kang, 4 Mar. 2012. Thailand: 1 ♀ (10.71 mm) (NCHUZOOL 15494), Ranong mangroves, 27 May 2012.

Diagnosis.

Carapace ( Figs 2A , 3A, F ) trapezoidal, 1.45 times as broad as long (N = 127, SD = 0.06), longitudinally convex, broadest between lateral teeth 2 (exorbital angle included), surface sparsely but regularly furnished with short, stiff setae; front broad, divided into two broad lobes, medially concave; lateral margins markedly converging posteriorly, interrupted by four notches, delineating five teeth (including exorbital angle), exorbital angle most distinct, posterior two indistinct; posterolateral facet faintly defined, decorated by two oblique granular ridges. Infraorbital ridge ( Figs 2B , 3C ) distinctly sexual dimorphic, males with 47-61 tubercles, medial seven closely set, almost fusing, lateral ca. 20 tubercles slightly vertically elongated; females with 33-42 isomorphic tubercles. Chelipeds ( Figs 2C , 3D ) symmetrical, in males more elongated and robust, palm 2.2 times as long as broad, length of palm approximately 1.8 times longer than dactyl (N = 20), pollex of chela with low sinuous tooth along cutting margin, dactylus with distinct triangular molar. Ambulatory legs elongated, meri broad, merus of P4 distally armed with several short spines on anterior margin; anterior margins of all ambulatory legs fringed with setal patches. G1 ( Fig. 7 A–D ) long, slender, distal process triangular, distinctly curved outward.

Distribution.

The Bay of Bengal, Southeast and East Asia: China (Zhejiang; Fujian; Guangdong; Hainan), western Taiwan (including Kinmen), Vietnam, Malaysia (Selangor; Sarawak; Labuan), Singapore, Brunei, Thailand, Myanmar (Mergui), and eastern India (Tamil Nadu, Godavari Delta) ( Fig. 1 ).

Habitat.

At Wazihwei Wetland, estuaries of Danshuei River, northwestern Taiwan, this species is found along shores with substantial freshwater influence, on banks with substrates plastic-muddy, somewhat distant from mangrove stands.

Remarks.

According to previous descriptions (De Man 1888, Dai et al. 1986, Dai and Yang 1991), the infraorbital ridges of M. elegans bear 50-60 tubercles in males and 35-40 tubercles in females. In the present study of 21 males and 19 females, CW ranging from 7.7 to 15.9 mm, and the range of variation is slightly wider than previously reported, being 47-61 in males and 33-42 isomorphic tubercles in females (Table 2 , Fig. 8 ).

Figures

Figure 1. Collection sites (solid symbols) for species of the genus Metaplax used in this study: green rhombus for M. elegans; red circles for M. longipes; blue triangles for M. sheni; and purple squares for M. tredecim. Empty symbols mean the additional records from references (see synonym lists for each species).

Figure 2. Metaplax elegans De Man, 1888 (A-C NCHUZOOL 15496, male, 12.7 mm), M. longipes Stimpson, 1858 (D-F ZRC 2019.0581, male, 14.9 mm), M. sheni Gordon, 1930 (G-I NCHUZOOL 15466, male, 9.9 mm), and M. tredecim Tweedie, 1950 (J-L paratype, ZRC 1964.7.14.4 - 18, 16.2 mm). A, D, G, J, A carapace B, E, H, K left infraorbital ridge C, F, I, L outer view of right cheliped. Scale bars: 1.0 mm.

Figure 3. Metaplax elegans De Man, 1888. A Dorsal view B ventral view C left infraorbital ridge D right cheliped A-D male (CW 12.7 mm; NCHUZOOL 15496; Dongshih, Chiayi County, Taiwan) E, F live coloration E photo taken in Gaomei, Taichung, Taiwan (specimen not collected) F-G male (CW 13.1 mm; NCHUZOOL 15489; Kinmen, Taiwan) G the typical habitat (Gaomei, Taichung, Taiwan). Scale bars: 2.0 mm.

Figure 7. Metaplax elegans De Man, 1888 (A-D NCHUZOOL 15496, male, 12.7 mm), right G 1; M. longipes Stimpson, 1858 (E-H ZRC 2019.0581, male, 14.9 mm), right G 1; M. sheni Gordon, 1930 (I-L NCHUZOOL 15466, male, 9.9 mm), right G 1; and M. tredecim Tweedie, 1950 (M-P paratype, ZRC 1964.7.14.4 - 18, 16.2 mm), left G 1. Scale bars: 0.5 mm (A-H, M-P); 0.2 mm (I-L).

Figure 8. The number of infraorbital tubercles and lobes plotted as a function of carapace width (CW) of Metaplax elegans De Man, 1888, M. longipes Stimpson, 1858, M. sheni Gordon, 1930, and M. tredecim Tweedie, 1950.