Alox rugosum Stimpson 1858
Creators: name: Galil, Bella S.
name: Ng, Peter K. L.
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Leucosiidae
Alox
Alox rugosum

description: Alox rugosum (Stimpson, 1858)
(Figs. 2 C, D, 7A–G, 8B, D–K)
Material examined. 1 male (7.3 mm) (MNHN-IU-2013-8854), 1 female (8.0 mm) (MNHN-IU-2013-17888), stn PR69, Rempi Area, south of lagoon inside bay, 05°01.6'S 145°48.1'E, 2–15 m, 20.11.2012; 1 male (5.8 mm) (ZRC 2015.267), stn PB12, Kranket I., west side, 05°11.8'S 145°48.8'E, 7–15 m, 11.11.2012; 1 immature female (5.9 mm) (ZRC 2015.268), stn PD19, Alexishafen, south Megas Islet, 05°05.4'S 145°48.5'E, 3–10 m, 13.11.2012; 1 female (10.0 mm) (MNHN-IU-2013-17896) stn PD 57, Gosern I., 05°09,4'S 145°48,3'E, 1–4 m, 29.11.2012.
Description. Carapace (Fig. 7A –G) laterally expanded, 1.5 times as wide as long. Carapace irregularly rimmed, dorsal surface prominently sculpted, pitted, irregularly covered with coalesced flattened granules, resembling coral rubble. Front narrow, produced, upcurved, bilobed, medially deeply pitted. Anterior margin of carapace vertical. Antennule well developed, basal antennular article operculiform, rugose, entirely sealing subovate antennular fossa. Antennae folded in orbital hiatus without gap. Orbits small, rounded, visible in dorsal view; ocular peduncle nearly seals orbit when retracted. Third maxillipeds concealing buccal cavity, closely set with flattened granules (Fig. 8 B); merus with pointed apex, outer margin convex, surface with median shallow depression; ischium twice as long as merus along inner margin.
Subhepatic region with narrow groove parallel to anterior margin of carapace, fungiform granules inserted in groove, margin with obtuse, granular, facet medially, visible in dorsal view. Lateral margins of carapace subquadrate, swollen, forming granular rim. Posterolateral margin with granular angular facet submedially. Posterior margin slightly produced, narrow, bilobate. Postfrontal median longitudinal ridge of irregular width. Bottom of irregular depression between marginal rim, swollen branchial regions lined with fungiform granules. Branchial regions swollen, irregularly pitted. Granule-lined irregular grooves separate cardiac, intestinal regions from branchial regions. Intestinal region swollen. Branchiostegal region covered with obsolete granules externally, large fungiform granules interspaced with small rounded granules interiorly.
Chelipeds (Fig. 7 E) subequal, robust, covered with flattened granules. Cheliped merus with large tubercle distally on posterior margin; palm inflated, granular, distally pitted; fingers 1.5 as long as palm; dactylus with longitudinal rows of closely spaced granules on outer surface; pollex, wider than dactylus, with carinate ventral margin; cutting edges with minute teeth. Ambulatory legs stout, short, closely granular, diminishing in size posteriorly; meri with single granular row dorsally, 2 rows ventrally; propodi with row of conic granules ventrally; dactyli slender, longer than propodi, studded with conic granules, terminating in incurved cornute claw (Fig. 8 D).
Thoracic sternites with large, granule-lined fossae. Male, female abdominal cavity deep, reaching buccal cavity. Male abdomen with granular interrupted grooves on either side of median ridge, telson triangular, elongated (Fig. 8 E). Gl straight along entire length, dorsoventrally flattened, distally slightly dilated, setose, apex pointed, with slit-like opening (Fig. 8 F, G). Female abdominal somites 1, 2 narrow, horizontal, distinctly granular; somites 3–6 fused, shield-like, divided into 3 parts by 2 shallow submedian furrows; telson laciniate. Vulvae large, nearly rectangular; directed vertically.
Colour in life. Carapace and legs bone-coloured with pale orange blotches, female abdomen with 2 pairs of brown dots (Fig. 2 C, D).
Remarks. We refer the present specimens to A. rugosum (Stimpson, 1858) (type locality: “Loo Choo”, see discussion Tan & Ng 1995: 131) with doubt. In the general appearance of the carapace, with dorsal surface prominently sculpted, pitted, and irregularly covered with coalesced flattened granules, it is closest to this species. The present specimens nevertheless differ slightly from most of the specimens previously referred to A. rugosum (cf. Tan & Richer de Forges 1993: fig. 4C, D; Tan & Ng 1995: fig. 12D, pl. 6D) in possessing a more distinct depression medially on the dorsal frontal surface; the male abdomen has more distinct granular interrupted grooves on either side of the median ridge, the rounded obtuse angle on hepatic margin with a shallow oval depression is not distinct, and the male telson is proportionately shorter. The specimens from Papua New Guinea most closely resemble in carapace form those previously reported from Gisser I. near Ceram in the Moluccas, Indonesia and figured as A. rugosum by Tan & Ng (1995: pl. 7A, B). Considering the substantial variation in the carapace form in A. rugosum, as well as the similarity of the G1 structures of the present specimens (Fig. 8 F, G, I, J) to those figured for A. rugosum s. str. (cf. Tan & Ng 1995: fig. 12H, I), it would be premature to recognize the present material as a new species.
Geographical distribution. This species is known only from Japan to New Caledonia (Tan & Ng 1995). New record for Papua New Guinea.
description: Published as part of Galil, Bella S. & Ng, Peter K. L., 2015, Leucosiid crabs from Papua New Guinea, with descriptions of eight new species (Crustacea: Decapoda: Brachyura), pp. 451-486 in Zootaxa 4027 (4) on page 455, DOI: 10.11646/zootaxa.4027.4.1, http://zenodo.org/record/234517