Lybia leptochelis ( Zehntner, 1894 )

Mendoza, Jose Christopher E. & Ng, Peter K. L., 2011, The Polydectinae Dana, 1851, of the Philippines, with description of a new genus for Lybia hatagumoana Sakai, 1961 (Crustacea: Decapoda: Brachyura: Xanthidae), Zootaxa 3052, pp. 51-61 : 52-53

Lybia leptochelis ( Zehntner, 1894)

( Fig. 1 A)

Ceratoplax leptochelis Zehntner, 1894: 174 , pl. 7 fig. 9 (type locality: Ambon, Indonesia). — Tesch 1918: 202, 203.? Lybia leptochelis — Balss 1938: 71.

Lybia leptochelis — Barnard 1947: 364; 1950: 251, fig. 46c, e. — McNae & Kalk 1958: 82. — Sakai 1967: 78. — Guinot 1967: 274; 1976: 71, figs. 16C, c, 21E, F, 22C, pl. 2 fig. 2. — Serène 1968: 88; 1984: 29, fig. 4, pl. 1 fig. F. — Kensley 1981: 44. —Ng et al. 2008: 201 (list).

Material examined. 1 female, 5.5 × 4.4 mm ( ZRC 2011.0761), tangle net, Balicasag Is., P. Ng et al., May 2004; 1 female, 3.3 × 2.7 mm (MNHN-IU-2011-5395), stn L 42, 80–90 m, “lumun-lumun”, Balicasag Is., PANGLAO 2004, 2 Jul. 2004; 1 male, 6.2 × 5.8 mm ( ZRC 2011.0762), 1 ovig. female, 6.5 × 6.0 mm ( ZRC 2010.0146), 1 male, 4.7 × 3.4 mm, 1 female, 6.4 × 4.8 mm ( ZRC 2011.0763), stn B11, 2– 4 m, coral rubble, Pamilacan Is., PANGLAO 2004, 11 Jun. 2004; 1 ovig. female, 6.5 × 4.5 mm ( ZRC 2011.0764), stn B22, 15– 20 m, rubble on mixed bottom, Pamilacan Is., PANGLAO 2004, 24 Jun.2004; 1 male, 2.3 × 2.0 mm ( ZRC 2011.0765), stn T 1, 83–102 m, mud with many sponges, Bolod, Panglao Is., PANGLAO 2004, 30 May 2004; 1 female, 4.7 × 3.5 mm ( ZRC 2011.0766), stn B 2, 5 m, reef slope, Alona Reef, Panglao Is., PANGLAO 2004, 31 May 2004; 1 male, 3.7 × 2.9 mm, 1 female, 3.1 × 2.5 mm ( NMCR 27557), stn B 10, 3–14 m, reef wall with small caves, Momo Beach, Panglao Is., PANGLAO 2004, 10 Jun. 2004; 1 female, 5.0 × 3.7 mm ( ZRC 2011.0767), stn B14, 2– 4 m, coral rubble, Sungcolan Bay, Panglao Is., PANGLAO 2004, 16 Jun. 2004.

Remarks. The examined specimens, all from the Bohol Sea, agree well with the description and illustrations of L. leptochelis ( Zehntner, 1894) (type locality: Ambon, Indonesia), by various authors ( Zehntner 1894: 174, pl. 7 fig. 9; Guinot 1976: 71, figs. 16C, c, 21E, F, 22C, pl. 2 fig. 2; Serène 1984: 29, fig. 4, pl. 1 fig. F). This was the most common species of Lybia collected by the PANGLAO 2004 expedition, and usually obtained by the coral brushing technique (see Bouchet et al. 2009).

Guinot (1976: 72) commented that L. leptochelis and L. plumosa Barnard, 1947 (type locality: South Africa) were very similar in morphology, and that the two main characters used to separate them (e.g., the degree of setation and the colouration of the carapace) were quite difficult to use. She was able to show, however, that the dentition of the chelae in polydectines was apparently species-specific ( Guinot 1976: fig. 22), and that L. leptochelis has more teeth (9) on the cutting margins than L. plumosa (7). Serène (1984: 27, 28) distinguished L. leptochelis from L. plumosa by the following features: 1) fingers of the chelipeds with 9 or 10 teeth (7 or 8 teeth in L. plumosa ); 2) dactylus length equal to 1.65 times length of superior margin of palm of cheliped (equal to 1.9 times in L. plumosa ); 3) carapace covered with short tomentum, with scattered tufts of stiff setae particularly on the front (carapace covered with dense, plumose tomentum in L. plumosa ); 4) presence of black lines around the anterolateral lobes and pigmented ocelli on submedian, dorsal surface of carapace (no pigmentation on carapace of L. plumosa ); and 5) ambulatory legs relatively more slender, particularly P2 (ambulatory legs relatively stouter in L. plumosa ).

Guinot (1976: 74) remarked on the possibility that L. pugil ( Alcock, 1898) (type locality: Sri Lanka) may be a synonym of L. leptochelis , an idea first mooted by Balss (1934), as she noted that the P2 of both L. leptochelis and L. pugil (as Melia pugil , cf. Alcock & Anderson 1899: pl. 38 fig. 5) was as robust as the P5 (vs. P2 more slender than P5, as in L. caestifera ( Alcock, 1898) , cf. Alcock & Anderson 1899: pl. 38 fig. 4). She nevertheless hesitated to formally synonymize the two as she had no material from Sri Lanka (as Ceylon) and she noted that the illustration by Alcock & Anderson (1899) showed a more areolated carapace in L. pugil .

Likewise, the live colouration of the Philippine material ( Fig. 1 A) is quite similar to that of the L. leptochelis described and figured by Barnard (1950: 251, fig. 46c) and that of L. caestifera figured by Sakai (1976: pl. 180, fig. 2). The three species, L. leptochelis , L. pugil and L. caestifera , are similar to each other in morphology, and it is possible that the three are synonyms. This matter can only be resolved through a renewed examination of the types and/or of topotypic material. For the moment, we identify the Philippine material as L. leptochelis .

Figures

FIGURE 1. Live colouration of Philippine Polydectinae species. A, Lybia leptochelis (Zehntner, 1894), male, 6.2 × 5.8 mm (ZRC 2011.0762), Pamilacan; B, Polydectus cupulifer (Latreille in Milbert, 1812), female, 16.1 × 13.3 mm (ZRC 2011.0768), Balicasag; C, D, Tunebia hatagumoana (Sakai, 1961), C, male, 3.9 × 3.9 mm (ZRC 2011.0772), Panglao; D, specimen not examined (coll. off western coast of Batangas; stn DW 2861, LUMIWAN 2008).