Discoplax michalis, Ng, Peter K. L. & Shih, Hsi-Te, 2015

Ng, Peter K. L. & Shih, Hsi-Te, 2015, The land crabs of the Discoplax longipes A. Milne-Edwards, 1867 species group, with description of a new species from Guam (Crustacea: Decapoda: Brachyura: Gecarcinidae), Zootaxa 3980 (3), pp. 379-405 : 388-389

Discoplax michalis n. sp.

( Figs. 4 , 5 , 6 E, F, 7G, H, 9, 10E, F, K, L, 14E–H, 15C–H, 16C, D)

Cardisoma longipes —Ng 1998: 1151 (part, Guam).

Discoplax longipes — Ng & Guinot 2001: 317 (part), figs. 2A, 4A, 5–8, 12A, 13 ( Guam); Paulay et al. 2003: 507 ( Guam); Ng et al. 2008: 215, fig. 158 (no new locality); Shih 2013: 27, fig. 8 (no new locality).

Material examined. Holotype: male (54.1 × 47.2 mm) ( ZRC 2000.2054a), in limestone cave, about 50 m from beach, behind beach forest, Faifai Beach, near Gun Beach, Tumon Bay, Guam, coll. P.K.L. Ng & G. Paulay, April 2000. Paratypes: Guam: 3 males (48.9 × 43.1 mm, 50.6 × 43.0 mm, 50.7 × 43.7 mm), 1 female (47.8 × 40.3 mm) ( ZRC 2000.2054b), 1 male (QM), same data as holotype; 2 ex–ovigerous females (47.8 × 40.3 mm, 52.7 × 45.9 mm) ( ZRC 2000.2052–2053), in limestone cave, about 50 m from beach, behind beach forest, Faifai Beach, near Gun Beach, Tumon Bay, coll. P.K.L. Ng & G. Paulay, April 2000; 3 males (56.8 × 49.0 mm, 44.2 × 38.3 mm, 41.8 × 36.0 mm), 3 females (66.2 × 56.5 mm [ovigerous], 65.9 × 56.8 mm, 36.3 × 31.0 mm) ( ZRC 2001.0701), 1 male, 1 female ( SMF), 1 male, 1 female ( NSMT), in limestone cave and adjacent limestone cliffs and beach, Faifai Beach, near Gun Beach, Tumon Bay, coll. P.K.L. Ng et al., 28 July–1 August 2001; 1 male (39.6 × 34.1 mm) ( ZRC 2001.0702), outside University of Guam guesthouse, Pago Bay, coll. P.K.L. Ng & H.-C. Liu, 1 August 2001; 1 male (69.7 × 57.8 mm) ( ZRC 2000.5072), no specific location, from University of Guam teaching collection, coll. between 1980–1990; 1 male (68.3 × 60.0 mm) ( ZRC 2000.0571), Piggy Cave, Mount Santa Rosa, coll. S. Bauman, 18 March 1996; 1 juvenile female (17.3 × 15.3 mm) ( ZRC 2001.1151), in cave, Ritidian, coll. 16 December 1992.

Diagnosis. Frontal, epigastric, epibranchial, anterior part of mesobranchial regions covered with numerous small rounded granules, those on anterior part flattened; mesogastric, metagastric regions distinctly granulated; posterior part of meso-, metabranchial regions with prominent striae, granules; epigastric regions well defined, margin relatively sharp; postorbital cristae relatively strong ( Figs. 4 A–C, 5, 6E, F, 7G, H). Surfaces of adult chelae distinctly granulated to rugose ( Fig. 4 A, B, E). Ambulatory legs long; ratios of maximum length to maximum width of second to fourth ambulatory meri 3.6–4.4, 3.5–4.3, 2.9–3.6, respectively; ratios of maximum length to maximum width of second to fourth ambulatory legs (dactylus, propodus, merus) 13.9–16.0, 13.5–15.0, 11.1–12.1, respectively; surfaces covered with distinct granules and/or striae, appearing very rugose; dorsal margins of merus prominently granulated; lateral margins of propodus, dactylus lined with strong, stiff spines or setae, propodus always distinctly armed ( Figs. 4 A, 5, 10E, F, K, L). Male abdomen relatively less broad; lateral margin of somite 6 gently convex ( Figs. 4 D, 9). Adult G1 gently curved to almost straight when viewed from ventral perspective; tip bent at an angle of about 90° from vertical; outer margin of distal part meets curved distal part of pectinated part abruptly, forming gentle shelf–like structure; base of pectinated distalmost part (outer marginal view) prominently broad; inner surface with relatively deep median longitudinal depression ( Figs. 14 E–H, 15C–H, 16C, D). Guam.

Etymology. The species is named after Michael Türkay, senior carcinologist at the Senckenberg Museum, and the acknowledged dean of land crab systematics. His series of important papers in the 1970s are landmark publications for the study of these crabs. The name is derived from the Greek for Michael, “Μιχάλης” or " Michalis ”, and is used as a noun in apposition.

Remarks. See discussion for D. longipes s. str. The ecology of this species has been described and discussed at length by Ng & Guinot (2001) (as “ D. longipes ”). We have nothing to add and readers are requested to refer to that reference for more information.

Distribution. Known only from Guam.

Figures

FIGURE 4. Discoplax michalis n. sp., holotype male (54.1 × 47.2 mm) (ZRC 2000.2054), Guam. A, overall habitus; B, dorsal view of carapace; C, frontal view of carapace; D, anterior thoracic sternum, telson and abdominal somites 4 – 6; E, outer view of left chela.

FIGURE 5. Discoplax michalis n. sp., overall habitus. A, paratype male (69.7 × 57.8 mm) (ZRC 2000.5072), Guam; B, paratype male (68.3 × 60.0 mm) (ZRC 2000.0571), Guam; C, paratype male (41.8 × 36.0 mm) (ZRC 2001.0701), Guam.

FIGURE 6. Discoplax species, dorsal views of carapaces. A, D. longipes A. Milne-Edwards, 1867, male (68.2 × 57.4 mm) (ZRC 2002.0050), Loyalty Islands; B, D. longipes A. Milne-Edwards, 1867, male (43.3 × 37.7 mm) (ZRC 2001.1150), Loyalty Islands; C, D. longipes A. Milne-Edwards, 1867, male (68.9 × 61.3 mm) (SMF 4293), Makatea, French Polynesia; D, D. longipes A. Milne-Edwards, 1867, male (57.0 × 50.2 mm) (SMF 6680), Niue; E, D. michalis n. sp., paratype male (68.3 × 60.0 mm) (ZRC 2000.0571), Guam; F, D. michalis n. sp., paratype male (41.8 × 36.0 mm) (ZRC 2001.0701), Guam.

FIGURE 14. Discoplax species, left G 1 s. A – D, D. longipes A. Milne-Edwards, 1867, male (68.2 × 57.4 mm) (ZRC 2002.0050), Loyalty Islands; E – H, D. michalis n. sp., paratype male (68.3 × 60.0 mm) (ZRC 2000.0571), Guam. A, C, E, G, ventral views; B, D, F, H, dorsal views; C, D, G, H, distal parts (denuded).