Labuanium politum (De Man, 1887)

Naruse, Tohru & Ng, Peter K. L., 2020, Revision of the sesarmid crab genera Labuanium Serène and Soh, 1970, Scandarma Schubart, Liu and Cuesta, 2003 and Namlacium Serène and Soh, 1970 (Crustacea: Decapoda: Brachyura: Sesarmidae), with descriptions of four new genera and two new species, Journal of Natural History (J. Nat. Hist.) 54 (7 - 8), pp. 445-532 : 452-455

Labuanium politum (De Man, 1887)

( Figures 1–4 )

Sesarma polita De Man, 1887, p. 654 [type locality: Sullivan Island, Mergui Archipelago]; 1887–1888 (1888), p. 189, pl. 13, figs 7–9; Tweedie 1940, p. 93; 1950, p. 346, figs 2c, 3a–d.

Sesarma politum: Alcock 1900, p. 422 .

Sesarma (Sesarma) polita: Tesch 1917, p. 190 .

Labuanium politum: Serène and Soh 1970, p. 401 ; Serène and Moosa 1971, p. 15; Serène et al. 1974, p. 26; Yang 1979, p. 48; Tan and Ng 1994, p. 82; Wee and Ng 1994, p. 82; Cuesta et al. 2006, p. 157, figs 6A–E; Ng et al. 2008a, p. 221, fig. 166, 2008b, p. 74; Rahayu and Setyadi 2009, p. 66; Ng et al. 2015a, p. 2.

Labuanium polita: Fransen et al. 1997, p. 124 .

Material examined

Lectotype. NHM 1886.52, 1 male, 18.7 × 17.1 mm, Sullivan Island , Mergui Archipelago, coll. J. Anderson, designated herein.

Paralectotypes. MNHN-IU-2017-8026 (ex. MNHN-B16748 ), 1 female, 25.8 × 23.6 mm, Mergui Archipelago; RMNH D 18 , 1 male, Sullivan Island , Mergui Archipelago, Andaman Sea, Myanmar, coll. J. Anderson, 25 November 1881 – 13 April 1882.

Others. SMF 10004, 1 female, 34.5 × 31.0 mm, General MacArthur , East Samar, Philippines, 11.25°N, 125.5417°E, coll. W. Lobin, August 1978; ZRC 2003.0381, 6 males, 32.0 × 28.2–40.4 × 36.3 mm, 3 females, 32.0 × 28.6 − 38.2 × 34.3 mm, Laboc River , Bohol, Philippines, coll. P.K.L. Ng et al., 28–29 July 2003; RUMF-ZC-5411, 1 male, 37.0 × 33.0 mm, 1 female, 35.4 × 31.3 mm, same data as ZRC 2003.0381; ZRC 2013.0382 , 2 males, 32.8 × 29.4, 39.8 × 33.9, PANGLAO 2004, stn. M51, Mayacabac, Panglao Island , Philippines, 9.613333°N, 123.87°E, coll. PANGLAO 2004, 30 June 2004; ZRC 2013.0383 , 2 males, 34.2 × 30.0, 26.7 × 24.2 mm, PANGLAO 2004, stn. M57, Sungcolan inlet, Panglao Island , Philippines, 9.633333°N, 123.8317°E, coll. PANGLAO 2004, 4 July 2004; ZRC 2018.0050 , 2 males, 26.8 × 23.9, 30.5 × 27.3 mm, Baranggay Racat , Municipality of Sta. Ana, Cagayan Province, Philippines, 18.40048°N, 122.1263°E, coll. J.C.E. Mendoza and T. Naruse, 23 April 2007; ZRC 1965.7 .29.58, 1 male, 40.8 × 36.2 mm, Labuan, Borneo , Malaysia, coll. G. Nunong, 1938; RUMF-ZC-2358, 2 males, 30.2 × 26.4, 32.1 × 28.8 mm, 2 females, 26.0 × 23.9, 30.9 × 28.0 mm, Pulau Ubin , Singapore, 1.410617°N, 103.9788°E, after Chek Jawa, nipah palm with stream, coll. P.K.L. Ng et al., 18 October 2012 .

Colouration

In life, carapace dorsal surface dark brown to khaki, gastric to intestinal regions with one wide and longitudinal dark line. Chelipeds and ambulatory legs dark red to dark brown ( Ng et al. 2015a, figs 2–4).

Distribution

Indo-West Pacific: India ( Alcock 1900); Mergui Archipelago [type locality: Sullivan Island] and western part of Indian Archilpelago (De Man 1887, 1887–1888 (1888)); Peninsular Malaysia ( Tan and Ng 1994); Labuan,Borneo ( Tweedie 1950); central and northern Philippines ( Cuesta et al. 2006; Ng et al. 2008a; present study); Singapore ( Ng et al. 2015a); Ambon; Timika, Indonesian Papua ( Serène and Moosa 1971; Rahayu and Setyadi 2009).

Remarks

When De Man (1887) described Sesarma polita , he examined four males and two females, although no holotype was designated. Of these six specimens (all syntypes), we were able to examine one male ( NHM 1886.52 ), one female ( MNHN-B16748 ) and one male (RMNH D 18 ). The whereabouts of the remaining three specimens are not known. A male specimen ( NHM 1886.52 ) from Sullivan Island , Mergui Archipelago, is here designated as the lectotype. This is necessary for stability as Sesarma polita is the type species of the genus and the present revision restricts the genus to the type species.

Ecological note

Labuanium politum is known to be associated with the nipah palm ( Nypa fruticans ) ( Ng et al. 2015a). Ng et al. (2015a) also noted that the species has been occasionally found among mangrove tree roots with no nipah palm patches around the area ( Rahayu and Setyadi 2009), although the specimens concerned may be vagrants.

Figures

Figure 1. Labuanium politum (De Man, 1887). Lectotype, NHM 1886.52, male, 18.7 × 17.1 mm (Mergui Archipelago). a, habitus, dorsal view; b, habitus, ventral view.

Figure 2. Labuanium politum (De Man, 1887). ZRC 2003.0381, male, 40.1 × 36.2 mm (Bohol, Philippines). a, habitus, dorsal view; b, anterior part of cephalothorax, anteroventral view.

Figure 3. Labuanium politum (De Man, 1887). ZRC 2003.0381, male, 40.1 × 36.2 mm (Bohol, Philippines). a–c, left chela; a, outer view; b, inner view; c, upper view; d, meri of right P4 and P5. Arrow denotes rim.

Figure 4. Labuanium politum (De Man, 1887). ZRC 1965.7.29.58, male 40.8 × 36.2 mm (Borneo, Malaysia). a, pleon and telson; b, left G1, ventral view; c, distal part of left G1, dorsal view. Scale bars: a= 5 mm; b, c= 1 mm.