Metaplax sheni Gordon, 1930

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 sheni Gordon, 1930 Figures 2 G–I , 5 , 7 I–L

Metaplax sheni Gordon, 1930: 525 (type locality: Amoy (= Xiamen), Fujian, China); Gordon 1931: 553, figs 31-32 (China: Xiamen, Fujian); Tweedie 1936: 69, fig. 15(5) (Singapore); Shen 1940a: 74, 95 (China: Zhejiang; Fujian); Shen and Dai 1964: 133, 1 unnumbered fig. (China: Fujian); Dai et al. 1986: 509, fig. 289 (3-4), pl. 72 (6) (China: Fujian); Chen 1991: 441, fig. 415 (China: Zhejiang); Dai and Yang 1991: 558, fig. 289 (3-4), pl. 72(6) (China: Fujian); Huang 1994: 598 (list; China); Tan and Ng 1994: 82 (Singapore); Kosuge et al. 1997: 182 (Vietnam: Haiphong); Kitaura et al. 2002: 684 (Vietnam: Haiphong); Davie and Nguyen 2003: 383 (Malaysia: Johor; Singapore); Huang 2008: 668 (list; China); Ng et al. 2008: 226 (list); Yang et al. 2008: 803 (list; China: Fujian).

Metaplax indica : Rathbun 1931: 100 (China: Fujian); Shen 1940a: 74, 95 (list; South China). (not M. indica H. Milne Edwards, 1852)

Materials examined.

China: 5 ♂♂ (8.6-12.8 mm) (NCHUZOOL 15465), Wuyuanwan, Xiamen, Fujian, coll. H.-T. Shih et al., 1 Aug. 2018. Taiwan: 1 ♂ (9.9 mm) (NCHUZOOL 15467), Kinmen. Vietnam: 1 ♂ (9.9 mm) (NCHUZOOL 15466), Dong Rui, Quang Ninh, coll. H.-T. Shih et al., 29 May 2016.

Diagnosis.

Carapace ( Figs 2G , 5A, B ) subquadrate, 1.45 times broader than long (N = 7, SD = 0.04), longitudinally convex, regions faintly defined; frontal margin sinuous, medially noticeably concave; lateral margin markedly converging posteriorly, furnished with a row of soft setae, interrupted by four notches, cutting into five teeth, anterior two marked, triangular, last two weak, indistinct. Infraorbital ridge ( Figs 2H , 5D ) of males with 16-20 lobes and tubercles, innermost tubercle more than twice as broad as the adjacent, followed by six broad tubercles, decreasing in size. Chelipeds ( Figs 2I , 5E ) of males subequal, markedly elongated, palm 2.8 times as long as broad, length of palm approximately 2 times longer than length of dactyl (N = 6), merus and palm subequal in length; both fingers about half-length of palm, deflexed; cutting edges of pollex with low, serrated lobe, dactylus bearing distinct triangular molar. Ambulatory legs slender, elongated, anterior margins of meri finely serrated; anterior margins of carpi and propodi line with thick tomentum. G1 ( Fig. 7 I–L ) elongated, relatively stout almost straight.

Distribution.

China (Zhejiang, Fujian), Taiwan (Kinmen), Vietnam (Khanh Hoa; Haiphong; Quang Ninh), and Malay Peninsula (including Singapore) ( Fig. 1 ).

Remarks.

One curious record of M. indica was reported by Rathbun (1931) from Tsimei, Amoy (= Jimei, Xiamen), along the coasts of Fujian. Other than this record, there have been no definite records of M. indica from China, despite that of Shen (1940a) citing that of Rathbun’s (1931). Given the considerable resemblance between M. indica (see Naderloo 2011: figs 15, 18 c–d; Naderloo 2017: figs 31.11e, 32.2, 32.3) and M. sheni , and the latter described from the region (Amoy) shortly before, it is reasonable to consider Rathbun’s (1931) record represented M. sheni .

Specimens collected from Kinmen, opposite Xiamen (Fujian, China), are confirmed as M. sheni based on molecular analyses (see below), being a new record to Taiwan.

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 5. Metaplax sheni Gordon, 1930. A, B dorsal view C ventral view D left infraorbital ridge E right cheliped F right side of carapace showing the five teeth of lateral margin. A, C Male (CW 12.8 mm; NCHUZOOL 15465; Xiamen, Fujian, China) B, D-F male (CW 9.9 mm; NCHUZOOL 15466; Dong Rui, Quang Ninh, Vietnam). 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).