CRUSTACEAN RESEARCH, NO. 35:108-116, 2006

Two new species of leucosiid (: Brachyura) from the Ryukyu Islands, Japan.

Tohru Naruse & Peter K. L. Ng

Abstract.— Two new species of leu­ from Nakagusuku Bay, Okinawa Island. One cosiid crabs of the genera Alox and new species belongs to the Alox Tan Ebalia are described. Alox uru, new & Ng, 1995, and the other to Ebalia Leach, species, is distinguished from all eight 1817. congeners by the shape of the carapace. Specimens are deposited in the Natural Alox rugosum is perhaps most similar History Museum and Institute, Chiba, Japan to the new species, but Alox uru differs (CBM) and the National Science Museum, in its carapace shape and the distally Tokyo, Japan (NSMT). The abbreviations swollen male first gonopod. Alox zalion CL, CW, Gl, and G2 are used for the cara­ too has distally swollen male first pace length, carapace width, male first gono­ gonopod, but A. uru differs from A. pod, and male second gonopod, respectively. zalion in having the male first gonopod distally spinose. Ebalia stellaris, new species, is distinguished from E. humilis by the characters of the cara­ pace and the cheliped. Ebalia stellaris can be also differentiated from Nursia Alox Tan &Ng, 1995 species by a combination of carapacial Alox uru, new species characters - lack of dorsal ridge, a (Figs, la, 2) salient junction of anterolateral and Material examined.— Holotype. Male, posterolateral margins, and a distinctly CL 4.4 mm, CW 5.8 mm, CBM-ZC 8906, off wider carapace. Minami-Ukibaru Island, Nakagusuku Bay, Ryukyu Islands, Japan (26° 18.066' N, 127°58.460' E, depths of 3 m), coll. T. Introduction Naruse & Y. Matsuo, SCUBA + dredging, 20 The leucosiid fauna of the Ryukyu Dec. 2005. Islands is not well known. Sakai (2004) listed 99 species of leucosiid crabs from Japan, 21 Description of holotype.— Carapace species of which are exclusively or common­ (Figs, la, 2a) subtriangular, CW 1.32 times ly recorded from the Ryukyus. Considering CL. Dorsal surface rough, frontal, branchial, the lower latitude of the Ryukyu Islands and intestinal regions covered with low mush­ its more tropical climate, with more exten­ room-like tubercles; median keel wide, later­ sive reefs, a more diversified leucosiid fauna ally sloping gradually, transversely forming is to be expected. Indeed, recent studies concave curve on midway to cardiac region, have discovered several new species and with a pair of bumps across intestinal region, new records (Takeda & Nakasone, 1991; bumps rounded, as high as frontal region; Takeda, 1995; Komatsu & Takeda, 1999; intestinal region rounded posteriorly, Marumura & Takeda, 2004). embossed by lateral deep grooves; branchial In the course of the faunal survey of region shallowly concave, dish-like, external­ Brachyura of the Ryukyu Islands, two new ly surrounded by low, broad rim. Front pro­ species of leucosiid crabs were obtained duced anteriorly, upturned in frontal view, TWO NEW LEUCOSIID CRABS FROM THE RYUKYUS 109 divided into two rounded, raised lobes by Gl (Fig. 2g, h) slightly sinuous, outer deep, short fissure. Anterolateral margin margin concave subproximally, subdistally, nearly straight, slightly concave posteriorly, not tapering gradually, distal half swollen, lacking hepatic lobe and fissures; posterolat­ with both dorsal, ventral surfaces covered eral margins subparallel, more or less with short spines, tip pointed, directed out­ straight but indented inwards at right angles wards. G2 (Fig. 2i, j) short, with spoon- at about two-thirds length of margin; posteri­ shaped tip. or margin visible in dorsal view, medially Coloration.— Alox uru, new species, is concave, produced posteriorly beyond later­ uniformly ivory in life, thus hardly discern- al expansion. Epistome narrow, buccal cav­ able from the dead coral and rubble. ern reaching imaginary line joining infraor­ Habitat.— Alox uru was collected at bital margins. Subhepatic region with blunt depths of 3-6 m in back-reef moat filled with lobe directed antero-laterally. Antennule well branches of dead corals. The place is also a developed, basal segment fully occupying cultivation area for seaweed, Cladosiphon fossae when closed. okamuranus (Chordariaceae), an aquacultur- Third maxilliped (Fig. 2b) with broad ally important species there. exopod, as wide as ischium, distally round­ Distribution.— Known only from ed, reaching beyond proximal half of merus; Nakagusuku Bay, Ryukyu Islands, Japan. ischium rectangular, inner margin about Etymology.— The name of the new twice as long as that of merus; merus with species derives from the Ryukyuan language sharp apex. "uru" (pebbles composed of broken pieces Chelipeds (Fig. la) subequal, surfaces of corals), alluding to its uru-like appear­ rough; merus stout, short, about three- ance. The name is used as a noun in apposi­ fourths of chela, anterior margin widely con­ tion. cave; chela (Fig. 2c, d) high, palm with low Remarks.— The genus Alox was estab­ granules on proximal outer to dorsal sur­ lished by Tan & Ng (1995) during their revi­ faces; immovable finger slightly longer than sion of the genus Oreophorus Ruppell, 1830, palm, high, proximal height about three- for species which have the basal segment of quarters of palm, tapering gradually towards the antennule fully occupying the fossae sharp tip which curves inwards and back­ when retracted, a distinctive pattern of cara- wards, distal two-thirds of inside of ventral pacial grooves and the presence of mush­ margin lined with granules; movable finger room-like granules on the dorsal surface of slightly longer than dorsal margin of palm, the carapace. They recognized eight species: flat, gently curving inwards and backwards; three species originally placed in cutting edges of both fingers with sparse, Oreophorus, one in Tlos Adams & White, low, acute teeth. 1849, and four new species. Alox uru, new Ambulatory legs (Fig. 2e) stout, short, species, can be distinguished from all its covered with large granules except for pos­ congeners by the shape of the carapace, viz. terior surfaces of meri, dactyli terminating in the protruding frontal region with a narrow sharp, incurving claw. base, almost straight anterolateral margin, Abdomen (including telson) (Fig. 2f) has­ the position of the junction between antero­ tate; first, second segments short, first seg­ lateral and posterolateral margins being rela­ ment mostly hidden by posterior carapace tively more posterior in position, and the margin with only distal-lateral angles visible; prominent indentation of the posterolateral third to fifth segments completely fused, margin. Alox rugosum (Stimpson, 1858) is proximal angle of third segment produced probably most similar to the new species in outwards, third to fifth segments twice as the general shape of the carapace, but Alox long as sixth segment; sixth segment sub- uru can easily be differentiated from A. rugo­ trapezoidal, as long as telson. sum by the absence of the hepatic protrusion 110 T. NARUSE &P.K.L NG

(vs. with distinct hepatic protrusion in A. nal region triangular, produced posteriorly rugosum), more strongly produced posterior beyond posterior margin of carapace, margin of the carapace and the intestinal branchial region sloping towards margins, region (vs. gently produced in A. rugosum), slightly concave just inside margins. .relatively shorter movable finger of the chela Anterolateral margin with concave anterior (slightly longer than dorsal margin of the part with small hump on subhepatic region, palm vs. distinctly longer than dorsal margin posterior part produced, junction with pos­ of the palm), and the distal half of the Gl terolateral margin produced, acute, repre­ being swollen and with both the dorsal and sents greatest width of carapace; posterolat­ ventral surfaces covered with short spines eral margin with a large blunt hump on pos­ (vs. distal half of the Gl with of constant terior two-fifths. Epistome reduced, anterior width, not covered by spines in A. rugosum). margin of buccal cavern reaching imaginary In its distally swollen Gl, A. uru is similar to line joining infraorbital margins. Antennule A. zalion Tan & Ng, 1995, but the former dif­ short, basal segments filling inner part of fers in that the distal part of the Gl is dense­ orbit. Eye well developed. ly covered by spines (vs. sparsely covered Third maxilliped (Fig. 3b) with broad by setae in A. zalion). exopod, as wide as ischium, distal end reaching distal third of merus; merus slight­ Ebalia Leach, 1817 ly shorter than ischium, with rounded apex. Ebalia stellaris, new species Chelipeds (Fig. 3c) symmetrical, sur­ (Figs, lb, 3) faces except for fingers covered by tiny tubercles; merus as long as chela, tubercles Material examined.— Holotype. of distal half larger than other parts of che- Ovigerous female, CL 2.4 mm, CW 3.6 mm, liped, anterior margin bearing a small hump CBM-ZC 8907, west of Ukibaru Island, medially, posterior margin lined with four Nakagusuku Bay, Ryukyu Islands, Japan rounded teeth; chela with moderately (26° 18.062' N, 127°58.463'E, depths of 16 swollen palm, lower margin convex; finger m), coll. T. Naruse & Y. Matsuo, SCUBA + straight, slightly directed downwards, dredging, 20 Dec. 2005. immovable finger as long as palm, movable Comparative material.— Ebalia humilis finger longer than palm; cutting edges lined Takeda, 1977: 1 ovigerous female, CL 2.8 with small, sharp teeth, no gape when mm, CW 3.4 mm, NSMT-Cr. 5489, holotye, closed. depth of 45 m, st. 15, Ogasawara Islands, Ambulatory legs (Fig. 3d) slender, short, Japan, 15 Jun. 1976, coll. M. Takeda & M. meri to propodi granulose, dactyli long, Imajima; 2 juvenile males, 1 female, CL 3.2 incurving. mm, CW 3.9 mm, 1 juvenile female, NSMT- Abdomen (Fig. 3e) wide, third to sixth Cr. 5490, paratype, st. 8, Ogasawara Islands, segments completely fused, but incomplete Japan. sutures still visible. Coloration.— Ebalia stellaris, new Description of female holotype.— species, is creamy white in life, with a pair of Carapace (Figs, lb, 3a) subrhomboidal, CW light khaki rings, each of which surrounds 1.5 times CL, with pairs of humps on mar­ the gastric hump. gins. Dorsal surface medially convex, cov­ Habitat.— Ebalia stellaris was collected ered with tiny tubercles, without distinct at depths of 16 m with very fine sandy sub­ ridges, regions ill-defined. Front deflexed stratum. downwards, with triangular margin, frontal Distribution.— Known only from region convex dorsally, sloping posteriorly, Nakagusuku Bay, Ryukyu Islands, Japan. gastric region with a pair of humps, cardiac Etymology.— From the Latin "stellaris" region with a smaller hump medially, intesti­ meaning star-shaped, alluding to the shape TWO NEW LEUCOSIID CRABS FROM THE RYUKYUS 111 of the carapace. hardwickii Leach, 1817, is also not very Remarks.— The genus Ebalia (type clear. It is supposedly a junior subjective species: Ebalia bryerii Leach, 1817, a junior synonym of Nursia lar (Fabricius, 1793), but subjective synonym of Cancer tumefactus this name also has two other synonyms, Montagu, 1808) currently contains more Parthenope lar Weber, 1795 (nomen nudum) than 70 species, but its taxonomy is far from and Parthenope lar Fabricius, 1798. In the stable. Ihle (1918) already indicated that Zoological Museum of the University of careful studies of the genus would probably Copenhagen in Denmark are type speci­ lead to their separation into several genera. mens labelled as Parthenope lar Fabricius, Serene & Soh (1976) also recognized its het­ 1798, which are identical to what is today erogeneity and commented "Ebalia is proba­ known as Nursia lar (Fabricius, 1793) (sec­ bly not represented in the Indo-Pacific ond author, unpublished data). Presumably, region" (Serene & Soh, 1976: 9). This issue Fabricius (1798) had decided that what he needs to be revised in the future. Among had named as Cancer lar in 1793 may be bet­ highly variable members in terms of outer ter accommodated in Parthenope and morphology, the carapace as well as the che- renamed it as a new species. This is not sur­ liped of E. humilis Takeda, 1977 are most prising as Nursia lar does superficially look similar to those of E. stellaris, new species. like many parthenopid species. The name by Ebalia stellaris, however, can be distin­ Weber (1795) was based on Fabricius' guished from E. humilis by clearer convexi­ (1798) manuscript which was not yet pub­ ties on the dorsal surface of the carapace, lished at that time. with covered with microscopically granules Ebalia stellaris, new species, has an inter­ (vs. lower convexities without microscopical­ mediate appearance that straddles the cur­ ly granules in E. humilis), larger subhepatic rent members of Ihle's (1918) groups A and and posterolateral humps (vs. humps much D. Superficially, E. stellaris belongs to Ihle's smaller in E. humilis), wider carapace (1.50 (1918) group D, as the species lacks any times CL vs. 1.21-1.22 times CL), and four ridge on the dorsal surface of the carapace. rounded teeth of the posterior margin of the The new species, however, differs from the chelied merus (vs. 3 acute teeth in E. members of group D (N. phylloides Ihle, humilis) (present study; Takeda, 1977: Figs. 1918 and N. dimorpha Balss, 1915) in pos­ 2AB.3B-D). sessing rounded large and small humps on The taxonomy of the genus Nursia middle of posterolateral margin and subhep­ Leach, 1817, is also unstable. Ihle (1918) atic region, respectively (vs. absent), a trans­ divided Nursia into four groups (A-D) by versely produced acute junction of anterolat­ the formation of the dorsal ridges of the eral and posterolateral margins (vs. round­ carapace. Serene & Soh (1-976) considered ed, bilobed in N. phylloides and blunt in N. that real Nursia should be limited for Ihle's dimorpha), and the presence of small hump group A, and the remaining groups be trans­ on middle of the anterior margin of the che- ferred to other existing or new genera. lipedal merus (see Ihle, 1918: Fig. 135; They, however, did not formally do so. This Balss, 1915: Figs. 8,9). problem was discussed in Komatsu & Ebalia stellaris is also similar to species Takeda (1999) (also see Tan & Ng, 1993) of Ihle's (1918) group A, such as N. lar but as yet, the genus has not been revised. (Fabricius, 1793), N plicata (Herbst, 1804), Recently, Komatsu & Takeda (2003) trans­ N. minor (Miers, 1879) and TV. rhomboidalis ferred two species previously placed in (Miers, 1879), in possessing a laterally Nursia (N. cornigera Nobili, 1905, and N. salient junction of the anterolateral and pos­ jousseaumei Nobili, 1905) to a new genus terolateral margins and the carapace width Nobiliella Komatsu & Takeda, 2003. The (defined as the maximum width at the mid­ actual identity of the type species, Nursia point of the carapace length) being distinctly 112 T. NARUSE & P. K. L. NG

Fig. 1. Alox uru, new species and Ebalia stellaris, new species, a, A. uru, male holotype, CW 5.8 mm, CBM-ZC 8906; b, E. stellaris, female holotype, CW 3.6 mm, CBM-ZC 8907. TWO NEW LEUCOSIID CRABS FROM THE RYUKYUS 113

Fig. 2. Alox uru, new species. Holotype, male, CW 5.8 mm (CBM-ZC 8906). a, carapace, dorsal view; b, third maxilliped, left; c, chela, left, outer view; d, chela, left, inner view; e, first ambulatory leg, left; f, abdomen and telson; g, Gl, left, ventral view; h, distal part of Gl, left, dorsal view; i, G2, left, ventral view; j, distal part of G2, left, distal inner view. Scales, 1 mm. 114 T. NARUSE & P. K. L. NG

Fig. 3. Ebalia stellaris, new species. Holotype, female, CW 3.6 mm (CBM-ZC 8907). a, carapace, dorsal view; b, third maxilliped, left; c, chela, left; d, firstambulator y leg, right; e, abdomen and telson. Scales, 1 mm. longer than the carapace length (about 1.5 fig. 44; Dai et al., 1986: PI. 7, Fig. 3; Chen & times). Ebala stellaris, however, differs dis­ Sun, 2002: Fig. 134) tinctly from them in the laterally sloping branchial regions (vs. plate like and lateral part upturned) and the intestinal region Acknowledgments being continuous with the posterior margin We are grateful to two anonymous of the carapace (vs. separated from each reviewers for their comments on this manu­ other by a transverse shelf) (cf. N. lar, script; and Dr. Hironori Komatsu (National Serene & Soh, 1976: PL 1, Fig. C; N. plicata, Science Musem, Tokyo) for facilitating to Sakai, 1976: PI. 27, Fig. 2; Sakai, 1999: PI. 6, examine comparative specimens. This study Fig. B; N. minor, Shen, 1937: Text-figs. 1, 2; was partially supported by the 21st Century Sakai, 1976: Text-fig. 45; Dai et al, 1986: PI. COE Program of the University of the 7, fig. 4; N. rhomboidalis, Sakai, 1976: Text- Ryukyus TWO NEW LEUCOSIID CRABS FROM THE RYUKYUS 115

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Pacificum Septentrionalem, a Republica Singapore. Crustaceana, 64: 40-47. Federata missa, Cadwaladaro Ringgold et , & , 1995. A revision of the Indo- Johanne Rodgers Ducibus, observavit et Pacific genus Oreophorus Ruppell, 1830 descripsit. Pars VI. Crustacea Oxystomata. (Crustacea: Decapoda: Brachyura: Proceedings of the Academy of Natural Leucosiidae). In B. Richer de Forges, (ed.), Sciences of Philadelphia, 10:159-163. Les fonds meubles des lagons de Nouvelle- Takeda, M., 1995. A new leucosiid crab, Arcania Caledonie, Etudes et Theses, volume 2. uenoi, from the Ryukyu Islands. Special ORSTOM, Paris: 101-189. Bulletin of the Japanese Society of Weber, F., 1795. Nomenclator entomologicus Coleopterology, 4:151-155. secundum Entomologian systematicam ill. , 1977. Crabs of the Ogasawara Islands, V. Fabricii adjectis speciebus recens detectis et A collection made by dredging. Memoirs of varietatibus. viii + 172 pp., Chilonii and the National Science Museum, 10:113-140. Hamburgi. , & Nakasone, Y., 1991. Three leucosiid crabs of the genus Philyra from Okinawa, the Ryukyu Islands, with description of a new Address: (TN & PKLN) Department of species. Bulletin of the National Science Biological Sciences, National University of Museum, Series A, Zoology, 17:19-24. Singapore, 14 Science Drive 4, Singapore 117543, Tan, C. G. S. & Ng, P. K. L, 1993. Praosia puncta­ Republic of Singapore. ta, a new genus and species of mangrove leu­ E-mails: (TN) [email protected]; (PKLN) cosiid crab (Decapoda, Brachyura) from [email protected]