Arcania tropicalis, Naruse, Tohru, 2014

Naruse, Tohru, 2014, Description of two new species of Arcania Leach, 1817, from the western Pacific Ocean and redescriptions of A. undecimspinosa De Haan, 1841, and A. elongata Yokoya, 1933 (Crustacea: Brachyura: Leucosiidae), Zootaxa 3814 (3), pp. 301-332 : 320-325

Arcania tropicalis n. sp.

( Figs. 18–21 )

Arcania elongata — Tan 1996: 1024 (part), fig. 2k–o.— Galil 2001: 176 (part).

Material examined. Holotype. NTOU B00111, 1 male, 27.6 × 23.3 mm, Kezailiao fishing port, Kaohsiung, Taiwan, coll. R. Yoshida, 17 July 2011.

Paratypes. Taiwan: NTOU B00113, 1 female, 32.5 × 29.6 mm, Dasi, coll. S.-H. Wu, 21 Aug. 1997.— NTOU B00112, 1 male, 23.7 × 21.0 mm, Dasi, coll. C.-W. Lin, 14 June 2002.— NTOU B00114, 1 ovig. female, 30.6 × 27.3 mm, Dasi, coll. J.-Z. Chang, 27 Sept. 2002.— ZRC 1997.0383, 1 female, 23.5 × 21.1 mm, Tachi, Ilan, coll. C.- C. Lin, from local commercial trawler, 20 Nov. 1987.— ZRC 1998.1202, 1 male, 26.1 × 22.0 mm, 1 female, 32.4 × 29.5 mm, Dasi, Ilan, coll. J.-C. Lim, 20 Nov. 1987.— ZRC 2013.0378, 2 females, 22.4 × 20.5, 22.7 × 21.1 mm, Nangfangau, Ilan, coll. P.K.L. Ng, 18 Nov. 1997.— ZRC 2001.0041, 1 male, 23.7 × 22.6 mm, 1 female, 31.2 × 28.3 mm, Dasi, Ilan, coll. K.-X. Lee, 2000.—NMMBCD 4024, 1 female, 22.5 × 20.0 mm, 2 juveniles, 12.4 × 11.7, 17.4 × 16.3, Kezailiao fishing port, Kaohsiung, 25 Apr. 2013; NMMBCD 4010, 2 males, ca.23.9 × 21.8, 25.2 × 21.7 mm, 1 female, 21.9 × 19.8 mm, Kezailiao fishing port, Kaohsiung, 2 Sep. 2013.—RUMF-ZC-2722, 2 females, 24.4 × 22.7, 24.8 × 23.1 mm, Kezailiao fishing port, Kaohsiung, coll. R. Yoshida, 17 July 2011.

Other material. China: ZRC 1968.2.1.10, 1 male, 24.6 × 22.0 mm, Hong Kong, CSM T/267.— ZRC 1968.2.1.9, 1 male, 18.1 × 17.4 mm, 1 ovig. female, 25.4 × 23.7 mm, Hong Kong, Cr. 5/65, stn. 28, T/354.— ZRC 1968.2.1.11, 1 male, 24.9 × 21.3 mm, Hong Kong, Cr. 5/65, stn. 29, T/359.

Philippines: MNHN-IU-2013-13312, 1 ovig. female, 28.0 × 25.4 mm, Balicasag Island, Bohol, 50–500 m, tangle net, coll. local fishermen, 28 Nov. 2001.—MNHN-IU-2013-13313, 1 male, 23.9 × 21.9 mm, Balicasag Island, Bohol, coll. J. Arbasto, Feb. 2004.— NMCR 39104, 1 female, 26.0 × 23.4 mm, Balicasag Island, Bohol, 50–500 m, tangle net, coll. local fishermen, 28 Nov. 2001.— NMCR 39103, 1 male, 23.8 × 21.0 mm, Balicasag Island, Bohol, coll. J. Arbasto, Feb. 2004.—NSMT-Cr 15792, 3 males, 22.0 × 20.7–26.0 × 22.7 mm, 1 ovig. female, 26.1 × 23.7 mm, Balicasg Island, Bohol, tangle nets, coll. M. Takeda, M. Manuel-Santos & H. Komatsu, Feb, 2003.—RUMF-ZC-2357, 1 ovig. 24.9 × 22.1 mm, Balicasag Island, Bohol, 50–500 m, tangle net, coll. local fishermen, 28 Nov. 2001.—RUMF-ZC-02871, 1 male, 25.4 × 22.2 mm, dry, Balicasag Island, Bohol, 2014.— ZRC 2012.0505, 3 males, 17.9 × 17.2–25.4 × 22.0 mm, Balicasag Island, Bohol, 200–300 m, tangle net, coll. local fishermen, June 2002.— ZRC 2009.0267, 1 female, 20.3 × 18.7 mm, Aurora, Luzon, AURORA Expedition, stn. CP2763, 44m, 4 June 2007.— USNM 65346, sex unknown (badly damaged), Malavatuan, Verde Island Passage, Philippines Expedition stn. 5276, 13.8208, 120.2458, 18 fthms (ca. 33m), Albatross, Agassiz beam trawl, 12 ft (ca. 3.7m), with mud bag, 17 July 1908.— USNM 65427, 1 male, 28.1 × 24.8 mm, 1 female, 34.1 × 30.6 mm, San Fernando, SW of Luzon Island, 16.5100 120.1850, Philippines Expedition stn. 5442, Albatross, Agassiz beam trawl, 25 ft (ca. 7.6m), 10–11 May 1909. RUMF-ZC-2870, 1 male, 22.1 × 20.4 mm, dry, off Cavite, Mar. 2013.—NSMT-Cr 7499, 1 female, 29.2 × 27.7 mm, coll. H. Motoo;

Vanuatu: SANTO 2006: ZRC 2009.0613, 1 male, 25.9 × 22.9 mm, NE Aore Island, Aimbue Bay, tangle net, stn. EP04, 89–109 m, 12 Sep. 2006.— ZRC 2009.0571, 1 male, 17.9 × 16.3 mm, S Tutuba Island, stn. AT51, 153– 166 m, coll. 30 Sept. 2006.— ZRC 2009.0482, 1 female, 26.6 × 26.0 mm, Scorff Passage, stn. AT88, 87– 115 m, 15°31.9’S 167° 15.0E, 12 Oct. 2006.— ZRC 2013.0379, 1 female, 20.9 × 18.7 mm, Segond Channel, stn. AT84, 71– 104 m, 12 Oct. 2006.— ZRC 2009.0617, 1 male, 26.7 × 24.5 mm, 1 juvenile, 13.4 × 12.4 mm, NE Urilapa Island, stn. AT 119, 87– 120 m, 19 Oct. 2006.—MNHN-IU-2013-13311, 1 male, 24.1 × 22.5 mm, ENE Tutuba Island, stn. AT48, 330– 341 m, 15°33.8’N 167°18.9’E, 30 Sept. 2006.

Description. Carapace roundly elliptical, dorsal surface densely, uniformly covered with columnar granules ( Figs. 18 , 19 a); pterygostomial, subhepatic regions evenly covered with rounded granules ( Figs. 18 b, 19b). Front divided into 2 blunt triangular lobes by blunt triangular gap, lobes weakly produced anteriorly, tip not acute ( Figs. 18 a, 19a). Carapace with subhepatic, anterolateral, lateral, posterolateral, posterior, intestinal spines. Anterolateral spines smallest, more distinct in small individuals, followed in size by subhepatic-lateral, posterolateral-intestinal, posterior spines; posterior spines with dorsoventrally compressed, wide bases; distal end of intestinal spines not reaching those of posterior spines. Branchiocardiac to branchiogastric grooves distinct, epibranchial, cardiointestinal grooves present in large individuals. Antennular fossae oblique, basal antennular segment with acutely triangular lobe on distoposterior margin, long setum on subdistal part of posterior surface. Mesial end of infraorbital margin forming sharp triangular spine. Anteromesial corner of pterygostomial region, anterolateral margin of buccal cavern forming laterally compressed triangular, sharp spines, these spines fitting closed exopod of mxp3; distance between spines large due to blunt exopod of mxp3.

Eyes fitting within orbit, only corneal part slightly exposed.

Mxp3 ( Figs. 18 b, 19b) sparsely covered with rounded granules; merus length about two-fifths of ischium; ischium, merus each with longitudinal groove on mesial third, half; female merus with longitudinal row of setae along longitudinal groove. Exopod narrowed at level of proximal half of merus, gap between narrowed part of exopod, merus thus fitting triangular spine of anterolateral margin of buccal cavern.

Male thoracic sternites 4–7 covered with rounded granules ( Fig. 19 b); granulation about equal to pterygostomial region. Sternal button of abdominal holding on anterior end of thoracic sternite 5 at lateral slope of thoracic cavity, button fitting proximolateral cup of somite 6. Penis coxal. Vulva on mesial end of thoracic suture 5/ 6 on somite 6; mesial end of vulva converged, sternal cover on sublateral part of anterior margin ( Fig. 21 ).

Cheliped moderately long, subequal ( Fig. 18 a). Merus shorter than chela, entirely covered with rounded, conical granules. Carpus, palm covered with minute granules, granules sparser on lower surfaces of carpus, absent in lower surface of palm. Fingers slender, without gape when closed, with 10–16 small teeth with much smaller teeth throughout. Ambulatory legs slender, merus longest of articles, merus to propodus covered with minute conical granules, sparser to absent from lower surfaces. Dactylus with low keels on mid-lines of mesial, lateral surfaces, keel on lateral surface flanked by rows of setae.

Abdomen ( Fig. 19 b) granular with rounded granules; somites 3–5 fused, with proximolateral protuberances well swollen, each protuberance higher, slightly wider than central part between protuberances. Lateral margins of somite 6 slightly convex. G1 ( Fig. 20 a–d) strongly curved dorsally, distal part weakly recurved anteriorly; distal end with complex flaps fringing opening. G2 ( Fig. 20 e) short, opening facing dorsally in situ.

Coloration. Body and cheliped merus reddish dorsally, with pink lines on the gastric and hepatic regions. Branchial regions near posterolateral margins lighter in color ( Fig. 18 a).

Geographical distribution. Taiwan (Kezailiao; Dasi; Tashi; Toucheng; Nangfangau); China ( Hong Kong); Philippines (Aurora; Bohol; Verde Island Passage; Samar Sea); Vanuatu.

Etymology. The species name is derived from the Latin tropicalis alluding its geographical distribution.

Remarks. Arcania tropicalis n. sp. is morphologically closest to A. elongata , but the new species can be easily distinguished from the latter by its strongly bent G1 (gradually curved dorsally in A. elongata ), and the shape of the vulvae, being converged mesially, with a sternal cover on the sublateral part of anterior margin in the new species ( Fig. 21 vs. fig. 17; see Table 1).

Tan (1996) studied material from the U.S. Fisheries Steamer Albatross and recorded A. elongata from 4 stations. Re-examination of these specimens revealed that three out of four lots of the specimens from the Philippines (USNM 1192285, stn. 5210; USNM 65346, stn. 5276; USNM 65427, stn. 5442) are A. tropicalis n. sp. (see Tan 1996: fig. 2k–o). The remaining male specimen from Hong Kong ( Tan 1996: fig. 1(B); USNM 1192284, stn. 5309) has conspicuously long posterolateral and intestinal spines, but the condition of the G1 is similar to that of A. elongata . It is thus possible that this belongs to an undescribed species.

Figures

FIGURE 18. Arcania tropicalis n. sp. Holotype. NTOU B 00111, male, 27.6 × 23.3 mm, Kaohsiung, Taiwan; a, habitus, with live coloration (photographed by R. Yoshida); b, cephalothorax, anterior view.

FIGURE 19. Arcania tropicalis n. sp. Holotype. NTOU B 00111, male, 27.6 × 23.3 mm, Kaohsiung, Taiwan; a, cephalothorax, dorsal view; b, cephalothorax, ventral view.

FIGURE 20. G 1 and G 2 of Arcania tropicalis n. sp. Holotype. NTOU B 00111, male, 27.6 × 23.3 mm, Kaohsiung, Taiwan; a, left G 1, mesial view; b, left G 1, ventral view; c, distal part of left G 1, mesial view; d, distal part of left G 1, lateral view; e, left G 2. Scales = 1 mm.

FIGURE 21. Right vulva of Arcania tropicalis n. sp. NTOU (NTOU B 00113), male, 32.5 × 29.6 mm, Yilan, Taiwan. Scale = 1 mm.