Sulaplax ensifer Naruse, Ng & Guinot, 2008, spec. nov.
Creators: name: Naruse, Tohru
name: Ng, Peter K. L.
name: Guinot, Danièle
Publisher: name: Zenodo
Year: 2008
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Hymenosomatidae
Sulaplax
Sulaplax ensifer

description: Sulaplax ensifer spec. nov.
(Figs. 3–6)
Material examined. Holotype. Male, 3.0 × 3.8 mm, MZB Cru 1653, station SULT-020, Air Mahambia, Lasori, Muna Island, Sulawesi Tenggara, Indonesia, coll. F. Bréhier & L. Deharveng, 25 Aug. 2001.
Paratypes. One male, 2.7 × 3.5 mm, 1 ovigerous female, 5.0 × 6.5 mm, ZRC 2007.0119, data same as holotype; 1 male, 3.0 × 3.7 mm, 1 female, 4.0 × 5.0 mm, MNHN-B30396, data same as holotype.
Description. Carapace (Figs. 3, 4 a, b) subcircular, wider than long, CW 1.22–1.32 times (n = 5) CL; dorsal surface flat, sparsely covered with short setae, surrounded by continuous rim, regions clearly separated by grooves, gastric region hexagonal, cervical groove branching near distal end, branches confluent with rim; rostrum vestigial, roundly produced downwards; lateral margin or side wall without angle or tooth, anterolateral margin slightly convex, lateral surface below posterolateral margin swollen laterally. Antennular fossa very shallow, separated medially by thin septum with upper part projecting anteriorly. Epistome with posterior margin produced and concave medially.
Eye (Fig. 4 a, b) slightly visible from dorsal view, base of ocular peduncle fused to orbit, immovable, developed from inner upper region at a distance with respect to base of basal antennal article; cornea without trace of black pigment. Third maxillipeds (Fig. 4 c) narrow, forming wide gape when closed; exopod long, reaching distal quarter of merus, with long flagellum; ischium short, with long, sharp distal inner extension; merus ovoid, midlength about 2 times length of ischium, inner and outer margins subparallel; dactylus slen- der, about 2 times length of propodus, distal end reaching beyond distal inner part of ischium in situ.
Female with obliquely elliptical vulvae, not raised (Fig. 6 a), along imaginary line joining anterior margins of P2 coxae on medial fused plate of thoracic sternum. Chelipeds of largest male (MZB Cru 1653, 3.0 × 3.8 mm) symmetrical, subequal in largest female (ZRC 2007.0119, 5.0 × 6.5 mm), left slightly larger; merus long, with flat ventral surface, ventral margins lined with short setae, ventral outer margin with subterminal tooth; carpus slightly longer than dorsal length of palm, outer surface rounded, dorsal inner margin lined with setae; chela (Fig. 5 b, c) long, palm with swollen outer surface, dorsal and ventral margins lined with setae, ventral line of setae continuous to distal end of immovable finger; fingers obviously longer than palm, flat, slightly incurving distally, with crossing acute tips, cutting edges blade-like. Ambulatory legs (Figs. 3, 5 a) extremely slender, P2 and P3 subequal in length, longer than P4, P5 shortest; merus with elliptical cross-section, with constant diameter throughout length, P2 and P3 meri as long as maximum width of dorsal rim of carapace; propodi with short setae, slightly shorter than respective meri; dactyli shorter than propodi, slightly incurving, inner margin lined with short setae, terminating in sharp spine, without subterminal tooth.
Male abdomen-pleotelson (Fig. 5 d) 4-segmented, third to fifth segments fused; first segment with proximal part placed below posterior margin of carapace, disto-lateral angles with rounded protuberance; second segment short, narrower than first and fused segments; fused segments subparallel in proximal half, narrowed to about half width in distal half. G1 (Fig. 5 e, f) curving outwards at distal half, distal part tapering simply, directing forwards, dorsal side of inner margin lined with long, stiff plumose setae; suture running from dorsal side of proximal part to outer margin of distal part. Female abdomen-pleotelson (Fig. 6 b–d) rounded; first segment short, distal margins of first and second segment slightly covering proximal margin of second and third segments, respectively; third abdominal segment to pleotelson fused, pleotelson demarcated from rest of abdomen by very thin suture externally; margin of inner surface of abdomen-pleotelson covered with thin membrane, membrane proximally connected to margin of cephalothorax cavity, forming internal brood cavity (Fig. 6 a, c); pleopods small, biramous (Fig. 6 e–h), present on second to fifth segments, completely contained inside abdominal cavity.
Eggs. The eggs are large and subcircular in shape, long axis is 1.10–1.26 mm (mean 1.19 mm, n = 10). One female (ZRC 2007.0119, 5.0 × 6.5 mm) had only 17 eggs, eight of which were held in the abdominal cavity (Fig. 6 c), and nine were in the cephalothorax cavity.
Etymology. From the Latin ensifer meaning “carrier of a sword,” alluding to the blade-like fingers of the chela. The name is used as noun in apposition.
Remarks. Sulaplax ensifer spec. nov. is superficially similar to C. xenomorpha Ng, 1991. In addition to the characters separating Sulaplax from Cancrocaeca (Table 1), S. ensifer can be differentiated from C. xenomorpha by its relatively long cheliped fingers which have blade-like cutting edges (Fig. 5 b, c) (shorter fingers with dentate cutting edges in C. xenomorpha, Ng 1991: fig. 5A), naked outer surface of the chela (densely covered by various lengths of setae in C. xenomorpha), a proportionately longer cheliped merus which reaches beyond anterior margin of carapace when stretched forwards (Fig. 3 a) (just reaching anterior margin in C. xenomorpha, Ng 1991: fig. 1), proportionally longer ambulatory dactyli when compared with their respective propodi (Figs. 3, 5 a) (proportionally shorter in C. xenomorpha, Ng 1991: fig. 5C–F), the horizontal anterior margin of the dorsal rim of the carapace being relatively narrower (Figs. 3, 4 a) (wider in C. xenomorpha, Ng 1991: Fig. 2 A), sparsely setose thoracic sternum (densely covered by setae in C. xenomorpha), and much larger size of the eggs (1.10–1.26 mm vs. 0.59–0.64 mm).
Sulaplax ensifer possesses the largest eggs (mean 1.19 mm, n = 10) and the smallest clutch size (17 eggs) known for any hymenosomatid crab (see Abele 1972; Ali et al. 1995; Barnard 1950; Lucas 1971; 1980; Lucas & Davie 1982; Ng & Chuang 1996; Naruse et al. 2005; Naruse & Ng 2007a, b). Lucas (1970: table 1; 1980: 202, table 4) reported that Amarinus lacustris (Chilton, 1882), which lacks free larval stages, carries ca. 35 eggs of 0.65–0.80 mm diameter, whereas Barnard (1950: 72) observed that a female of Neorhynchoplax bovis (Barnard, 1946) contained 13 juveniles under the abdomen. He also recorded that another female of N. bovis carried about 30 embryos in a less advanced stage. The egg and clutch sizes suggest that S. ensifer practices direct or highly abbreviated development.
description: Published as part of Naruse, Tohru, Ng, Peter K. L. & Guinot, Danièle, 2008, Two new genera and two new species of troglobitic false spider crabs (Crustacea: Decapoda: Brachyura: Hymenosomatidae) from Indonesia, with notes on Cancrocaeca Ng, 1991, pp. 21-40 in Zootaxa 1739 on pages 27-31, DOI: 10.5281/zenodo.181452