Helice epicure, Ng & Naruse & Shih, 2018

Ng, Ngan Kee, Naruse, Tohru & Shih, Hsi-Te, 2018, Helice epicure, a new species of varunid mud crab (Brachyura, Decapoda, Grapsoidea) from the Ryukyus, Japan, Zoological Studies 57 (15), pp. 1-11 : 2-10

Family Varunidae H. Milne Edwards, 1853 Subfamily Varuninae H. Milne Edwards, 1853 Genus Helice De Haan, 1833 (sensu K Sakai et al. 2006)

Helice epicure sp. nov. ( Figs. 1 , 2A , 3 ) urn:lsid:zoobank.org:act:A902CDDB-2E2A-4623-8E91-A0F613076E5E

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Material examined: Holotype: male (25.3 × 30.7 mm) (RUMF-ZC-5009), Miyara River (= R.), Ishigaki Island (= I.), coll. T. Naruse, 23 June 2011 . Paratypes: 1 male (19.4 × 23.5 mm) (ZRC 2014.0244), Funaura jetty and beach, Iriomote I., coll. N.K. Ng, Y. Cai & T. Naruse, 15 June 2000; 1 male (26.4 × 30.1 mm) (RUMF-ZC-3069), Fukari R., Iriomote I., coll. T. Naruse, 30 October 2010; 1 male (21.7 × 26.1 mm), 2 females (16.1-19.1 × 20.1-23.3 mm) (RUMF-ZC-5010), Fukari R., Iriomote I., coll. R. Yoshida & Y. Endo, 19 August 2016; 1 female (23.8 × 29.5 mm) (RUMF-ZC-3070), Fukari R., Iriomote I., coll. T. Naruse, 30 October 2010; 1 male (28.9 × 34.4 mm), 1 female (22.3 × 27.5 mm) (ZRC 2014.0204), Fukari R., Iriomote I., coll. T. Naruse, 30 October 2010; 1 male (18.8 × 23.3 mm) (NCHUZOOL 12898), Shira R., Iriomote I., coll. T. Naruse, 30 August 2015.

Others: 1 female (18.4 × 23.5 mm) (RUMF- ZC-5011), Sashiki, Okinawa I., coll. T. Naruse, 30 July 2007; 2 males (15.7-27.4 × 18.9-32.7 mm) (SMF-29177), Oyama, Ginowan City, Okinawa I., coll. W. Ishigaki, N. Isa & M. Miyagi, 20 August 1983; 1 female (18.7 × 23.7 mm) (ZRC 2014.0243), Shirase R., Kumejima, coll. KUMEJIMA 2009 Expedition, 19 November 2009; 2 males (17.1-17.5 × 21.1-21.6 mm), 2 females (13.0-14.2 × 16.1-18.3 mm) (NCHUZOOL 12899), Konase, Setouchi, Amami-Ohshima I., coll. T. Maenosono, 26 April 2012; 2 females (12.3- 17.0 × 15.0-20.0 mm), 1 male (16.4 × 18.5 mm) (RUMF-ZC-3071), Tekebu, Kasari, AmamiOhshima I., coll. T. Maenosono, 25 April 2012; 3 males, 14.3-18.0 × 17.2-21.0 mm), 5 females (14.4-20.1 × 17.7-24.1 mm) (RUMF-ZC-1576), Sashiki tidal flat, Okinawa Island, coll. T. Naruse and K. Kobayashi, 11 August 2011; 11 males (9.9-17.2 × 12.6-21.2 mm), 5 females (9.3-14.5 × 12.0- 18.2 mm) (RUMF-ZC-3072), Konase, Setouchi, Amami-Ohshima I., coll. T. Maenosono, 26 April 2012.

Comparative material: Helice formosensis Rathbun, 1931 : Holotype: male (25.6 × 31.1 mm) (USNM-55371), Giran (= Yilan), Taiwan, coll. Taihoku Normal School, August 1918. Others: 1 female (12.5 × 15.8 mm) (NCHUZOOL), estuary of Gaoping R., Kaohsiung, Taiwan, coll. 29 November 2004; 1 female (21.7 × 27.5 mm) (NCHUZOOL), Yuanli , Miaoli, Taiwan, coll. 5 March 2006; 1 male (27.0 × 31.4 mm) (NCHUZOOL), Anping , Tainan, Taiwan, coll. 26 March 1998; 1 male (18.1 × 21.5 mm) (NCHUZOOL), Haishangu, Hsinchu, Taiwan, coll. 16 March 2006; 1 female (19.6 × 25.5 mm) (NCHUZOOL), Cingluo,

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Penghu, Taiwan, coll. 23 Nov 2006; 1 female (21.5 × 26.6 mm) (RUMF-ZC-5013), Dongshih, Chiayi, Taiwan, coll. 9 April 1996; 1 male (17.1 × 20.3 mm) (NCHUZOOL), Jhuwei, New Taipei City, coll. 25 October 2009; 1 male (17.2 × 20.5 mm) (NCHUZOOL), estuary of Houlong R., Miaoli, Taiwan, coll. 14 November 1992; 2 males (17.9 × 22.0-22. 3 mm) (NCHUZOOL), Cingluo, Penghu, Taiwan, coll. 27 June 2006; 2 males (16.8-23.9 × 20.8-27. 7 mm) (NCHUZOOL), 4 females (13.9- 19.4 × 17.2-24. 5 mm) (NCHUZOOL), Wenliao, Taichung, Taiwan, coll. 20 May 2002; 1 male (20.7 × 25.8 mm) (RUMF-ZC-5012), Gaomei, Taichung, coll. 12 July 2006; 4 males (16.4-19.0 × 19. 7- 23.4 mm), 5 females (18.4-20.0 × 23.6-25.5 mm) (NCHUZOOL), Wenliao, Taichung, Taiwan, coll. 20 August 2002; 1 male (14.7 × 16.9 mm), 1 female (19.9 × 24.5 mm) (NCHUZOOL), Cingluo, Penghu, coll. 23 November 2006; 1 male (23.3 × 27.3 mm) (NCHUZOOL), Dadu R., Shengang, Changhua, Taiwan, coll. 24 October 1995; 1 male (24.4 × 29.4 mm) (NMNS-040701), Taiwan, coll.

4 July 2001; 1 male (19.2 × 23.3 mm) (NMNS-04129); 2 males (22.0-24.3 × 28.6-29. 4 mm) (NTOU), Luodong, Yilan, Taiwan, coll. H.-S.

Lai, 2 November 1985; 2 males (1.7-14.3 × 14.8-17. 5 mm) (NTOU), estuary of Fengshan R., Hsinchu, Taiwan, coll. J.-F. Huang, 27 September 1987; 1 male (21.5 × 26.2 mm) (NTOU), Taichung, Taiwan, coll. J.-F. Huang, 29 March 1988; 3 males (7.8-12.9 × 9.7-16.2), 2 females (17.8-19.9 × 22.2-24. 3 mm) (ZRC 1999.1420), mangroves at Sinfeng, Hsinchu, Taiwan, coll. H.-C. Liu & C.D.

Schubart, 17 September 1999; 2 males (30.0-30.5 × 25.4-25.8 mm) ( ZRC.2001.0071), north Taiwan, coll. K.-X. Lee, no collection date; 1 male (19.5 × 23.4 mm), river mouth, Taiwan, coll. 29 November 2004. H. tridens De Haan, 1835 : Lectotype, 1 male (24.9 × 30.4 mm) ( RMNH-D188 ), Japan, coll.

von Siebold. Paralectotypes, 1 female, (23.1 × 28.3 mm) (RMNH-D189), Japan, coll. von Siebold; 1 male (25.0 × 29.8 mm) (RMHN-D190), Japan, coll. von Siebold. Others: 1 male (23.7 × 28.9 mm) (MNHN-B3476), Japan, no collector information, no collection date, from Leiden Museum. H.

latimera Parisi, 1918 (= H. tridens pingi Rathbun, 1931 , see K Sakai et al. 2006): Holotype of H.

tridens pingi, 1 male (25.7 × 31.1 mm) (USNM-59163), Hainan I., China, coll. C. Ping, November 1924. Others: 1 male (23.3 × 27.2 mm), 1 female (25.1 × 31.1 mm) (NCHUZOOL), Kinmen, Taiwan, coll. L.- R. Tung, 8 May 1989. H. tientsinensis Rathbun, 1931 : Holotype, 1 male (24.9 × 28.8 mm) (USNM-25431), Tientsin (= Tianjin), China, coll.

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M. Robb. Paratype, 1 female (26.2 × 33.0 mm) (USNM-171410), Tientsin, China, coll. May 1901.

Description: Carapace rectangular ( Fig. 1A ), distinctly broader than long, width to length ratio 1.17-1.29 (mean = 1.24, n = 43), dorsal surface convex, regions defined, punctuated, with single short seta on each punctum; cervical grooves indistinct, shallow, broad. Front sloping ventrally, frontal margin ( Fig. 1A ) bilobed, medially divided page 4 of 11

by deep, wide sinus; median sinus distinctly separating epi-, protogastric regions. Supraorbital margins gently sinuous, divergent posteriorly. Exorbital tooth distinct, tip pointing anteriorly; anterolateral, posterolateral margins confluent as lateral margin, with 3 branchial teeth behind exorbital tooth, first, second lateral teeth large, separated from anterior tooth by sharp V-shaped notch, third tooth small. Two low, oblique ridges on

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mesobranchial region, terminating laterally at notch between first, second and second, third teeth, respectively. Another low ridge present above base of P5. Infraorbital margins ( Fig. 2A ) granulate, setose, incomplete, not congruent laterally with exorbital tooth. Male with distinct suborbital ridge just below infraorbital margin, extending laterally to sub-branchial region; suborbital ridge with 19-26 (mean = 21.9, n = 22) well-spaced heteromorphic tubercles; mesial tubercles small, rounded, usually fused, non-mesial tubercles medially (especially below constricted portion to distal end of eye when retracted) large, vertically-elongated, inclined mesially ( Fig. 2A ). Female suborbital ridge weaker than male, with 23-29 (mean = 26.2, n = 15) small,

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isomorphic round granules.

Epistome broad, short longitudinally, sloping anteriorly, posterior margin with 2 submedian shallow concavities, median part produced roundly, margin granulated.

Eyes ( Figs. 1A , 2A ) well-developed, eye stalk weakly constricted near base of cornea. Third maxillipeds ( Fig. 1B ) leaving rhomboidal space when closed; ischium long, narrow; with longitudinal shallow groove, merus almost as long as ischium, widened distally, with diagonal groove running from distomesial corner of merus to proximolateral corner of ischium, mesial margin of diagonal groove setose; carpus articulated at distolateral corner of merus, auriculiform. Exopod

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narrow, long, reaching to distal third of lateral margin of merus, flagellum longer than width of merus.

Chelipeds ( Fig. 1A ) relatively short, stout, symmetrical in both male, female, much larger in male. Merus with triangular cross-section, lower margins lined with granules. Carpus rhomboidal in upper view, inner angle acute. Large male chela ( Fig. 1C ) longer than exorbital width; palm almost as long as high, outer surface weakly convex, smooth, upper part thin, upper margin keel-like, inner surface concave around articulation with carpus and base of immovable finger; movable finger longer than immovable finger, almost as long as lower margin of palm; both fingers (including occlusal margins) straight, directed slightly downwards, leaving narrow gap when closed, occlusal margin lined with small teeth.

Ambulatory legs ( Fig. 1A ) moderately long, slender; second ambulatory leg longest. Anteriorupper margin of meri with subdistal tooth. Mat of short setae on lower surfaces of propodus and distal portion of carpus of first ambulatory legs and propodus of second ambulatory leg. Dactyli long, slender, tapering to slender, acute, corneous tip.

Male pleon narrowly triangular ( Fig. 3A ), all somites and telson free; lateral margins with short setae; first pleonal somite arched, with transverse ridge; second somite narrow, short; third somite short, widest, lateral margin acutely convex; fourth somite broader but shorter than fifth somite; fifth somite with distal margin straight, lateral margins slightly concave; sixth pleonal somite subquadrate, lateral margins slightly convex on distal third, proximal margin straight; telson lateral margins subparallel, distal margin rounded, with transverse line of long setae on subdistally. Female pleon very broadly rounded.

Male thoracic sternites 3 and 4 ( Fig. 1B ) demarcated by straight suture; sternite 4 with lateral margins strongly concave, subdistal portions of lateral portion and anterior portion of sternopleonal cavity with setose area. Sternopleonal cavity narrow, reaching imaginally line joining almost distal end of bases of chelipeds, sutures between sternites 4-7 continuous mesially to near base of slope of cavity, ending in narrow depressions; median grooves present on sternites 5-7 each, but not connected to each other. Penis emerged from near anterior margin of thoracic sternite 8.

G1 ( Fig. 3B, C ) long, slender, gently curving dorsally along thorax, distally reaching to almost anterior margin of sternite 5 in situ; distal portion page 6 of 11

of G1 with terminal and subterminal (= palp) lobes, terminal lobe elongated, with thick corneous endpiece, genital opening lateral to base of terminal lobe; palp rounded, semitriangular, densely setose ( Fig. 3B, C ). G2 ( Fig. 3D ) short, broad, tip bilobed.

Female thoracic sternum similar in form but relatively broader. Female gonopore (= vulva; Fig. 3E ) on anterior two-fifth of sternite 6, conicallyshaped sternal cover developed from lateral margin, almost entirely covering vulva except for crescentic slit along anterior, mesial, posterior margins.

Etymology: The species name ‘epicure’ is used here as a Latin noun, derived from ‘epikouros’, a noun in Greek for ‘food lover’ or a person who takes particular pleasure in fine food and drink; this alludes to the late Professor Michael Türkay, a food connoisseur, who strongly believed in eating well and working hard. ‘Epikouros’ in Latin is ‘Epicurus’, also the name of a famous ancient Greek philosopher, whose insistence that nothing should be believed except that which was tested through direct observation and logical deduction made him a key figure in the development of science and scientific methodology.

Distribution: The new species is found in central to southern Ryukyus, including the islands of Amami-Ohshima, Okinawa, Kumejima, Ishigaki and Iriomote. Authors who recorded Helice from the Ryukyu Islands are almost certainly referring to the new species instead ( Table 1), although we were not able to examine their material. Our sampling covered most of the Ryukyu Islands (from Amami to Iriomote), and all the specimens belong to the new species. Paratypes are designated to the specimens collected from Yaeyama Islands (including the islands of Ishigaki and Iriomote), as the other main localities, including the islands of Okinawa and Amami, are located relatively far from the type locality (> 300 km).

“ Helice leachi Hess, 1865 ” was reported from the Ryukyus (e.g. Sakai 1976; Shokita et al. 1998; Nakasone and Irei 2003), but those records are now regarded as Pseudohelice subquadrata (Dana, 1851) instead ( Sakai et al. 2006).

Remarks: The taxonomy of the genus Helice De Haan, 1833 has been treated at length by K Sakai et al. (2006), and there is no need to discuss it further here. K Sakai et al. (2006) provided a key to identifying the extant four species. The main identification characters are the forms of the suborbital ridge (K Sakai et al. 2006: 16) and the structure of the G1 tip (K Sakai et al. 2006: 17).

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The new species does not bear any resemblance to Cyclograpsus latreilli H Milne Edwards, 1837 , which has been synonymized under Helice tridens (MNHN-B4647S) and Pseudohelice subquadrata (Dana, 1851) , a senior synonym of Helice latreilli H. Milne Edwards, 1853 (MNHNB3468S) by K Sakai et al. (2006), respectively.

Helice epicure sp. nov. can be clearly distinguished from H. tridens (De Haan, 1835) , H. latimera Parisi, 1918 , and H. tientsinensis Rathbun, 1931 by the shape of suborbital crista and/or number of granules on the suborbital ridge ( Table 2).

In the general morphology, the new species is most similar to H. formosensis . However, it can be distinguished from H. formosensis by the following characters: viz. the shape of the middle large tubercles of suborbital ridge (relatively smaller, each tubercle mesially high, well-spaced from each other ( Fig. 2A ) vs. relatively large, each tubercle medially high, densely lined in H. formosensis ( Fig. 2B )) and the base of the occlusal margin of the immovable finger of large male (almost straight ( Fig. 1C ) vs. deeply concave in H. formosensis ). The new species also resembles H. latimera and H. tientsinensis in the general form of the carapace, but it can be easily distinguished from H. latimera by the following characters viz. a) forms, including the numbers and types of tubercles on the suborbital ridge (see Table 2); b) the gap between the terminal and subterminal lobes on the tip of the G1 is broad (vs. narrow gap of G 1 in H. latimera ) (see K Sakai et al. 2006: 17, fig. 22a-b), and c) the female gonopore is raised, and rounded (vs. is slightly raised and slightly elongated in H. latimera ) (see K Sakai et al. 2006: 17, fig. 26). The new species can be easily distinguished from the H. tientsinensis in the following characters viz. a) forms, including the numbers and types of tubercles on the suborbital ridge (see Table 2);

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b) the gap between the terminal and subterminal lobes on the tip of the G1 is broad (vs. slightly narrower gap of G 1 in H. tientsinensis ) (see K Sakai et al. 2006: 17, fig. 21a-b), and c) the female gonopore is raised, and rounded (vs. is slightly raised and slightly elongated in H. tridens ) (see K Sakai et al. 2006: 17, fig. 25).

Molecular analyses and discussion

The phylogenetic tree of COI based on 658- bp segments ( Fig. 4 ) showed H. epicure sp. nov. and the H. latimera complex (including H. latimera , H. formosensis and H. tientsinensis ) to be sister. There are three haplotypes, named “Hep-C1”, “Hep-C2” and “Hep-C3” (accession numbers LC375187, LC375188, and LC375189, respectively), differing by ≤ 3 bp or 6.92% K2P divergence, among 17 individuals of the new species. The haplotype HRY-C1 is the most common one, found in 14 individuals from Iriomote, Ishigaki, Okinawa and Amami; HRY-C2 is found in one individual from Okinawa; and HRY-C 3 in two individuals from Kumejima and Amami.

With regard to Helice , the mean divergence within and between subclades (species or complex) are shown in table 3. The minimum divergence between H. epicure and the H. latimera complex is 2.97%, which is much larger (4.9 times) than the maximum divergence (0.61%) within members of the H. latimera complex. Therefore, this new species is supported by both its phylogenetic relationship ( Fig. 4 ) and its nucleotide divergence ( Table 3).

Although the minimum interspecific divergence 2.97% is smaller, compared with other taxa of the superfamily Grapsoidea , viz. 4.7% (between Helice tridens and the Helice latimera complex; Shih and Suzuki 2008); 4.66% (between Eriocheir japonica (De Haan, 1835) and E. hepuensis Dai ,

Male Female

H. formosensis 15-33 heteromorphic roundish tubercles, including 2-8 striated, 24-33 small, rounded, isomorphic tubercles mesial ones

H. latimera 64-67 vertically expanded, striated ridges 37-45 small, rounded isomorphic tubercles

H. tientsinensis 33-37 heteromorphic tubercles; clearly higher medially, laterally 26-37 small, rounded isomorphic tubercles confluent with one another

H. tridens 9-17 heteromorphic rounded tubercles, including 2-3 striated 15-28 small, rounded isomorphic tubercles mesial tubercles

H. epicure sp. nov. 19-26 heteromorphic roundish tubercles with several striated, 23-29 small, rounded isomorphic tubercles mesial ones

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1991) (GTR + G model; Chu et al. 2003); and 4.1% (for the Jamaican Sesarma reticulatum group; Schubart et al. 1998), this value is still greater than the 1.6% (between Neosarmatium africanum Ragionieri, Fratini & Schubart, 2012 and N. meinerti (De Man, 1887)) (p -distance; Ragionieri et al. 2009 2012).

The small interspecific divergence distance suggests that the insular H. epicure and the continental H. latimera complex diverged relatively recently in geological time. If the substitution page 9 of 11

rate of COI - 1.66%/106 yr for marine sesarmids ( Schubart et al. 1998) - is applied, then the two species separated about 1.8 million years ago (with the p -distance 2.97%). This suggests that this separation was the result of isolation by early Pleistocene glaciation events ( Haq et al. 1987; Woodruff 2003) around the Ryukyu Islands, when it separated from continental Asia, probably by the deep Okinawa Trough, while the Taiwan Island was still connected to China.

While H. epicure forms a distinct clade, its

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sister clade - the members of the H. latimera complex - remains unresolved ( Fig. 4 ) (see Shih and Suzuki 2008; Xu et al. 2011 2012). Shih and Suzuki (2008) have already suggested H. latimera , H. formosensis and H. tientsinensis may be a single species based on the unresolved clade. Recently, Xu et al. (2010 2011) analysed the morphometrics of H. latimera and H. tientsinensis . Based on morphological characters, the two species cannot be separated by cluster, discriminant or principal component analyses. In addition, intermediate forms of suborbital crenulation were found in Ningbo, Zhejiang, China, around the delta of Yangtze River; the northern population of which was closer to the “ tientsinensis - form” and the southern population the “ latimera - form”. These studies suggest that H. latimera and H. tientsinensis are probably conspecific. Similar morphometric studies including a morphologically distinct H. formosensis will be necessary to solve taxonomic issues among these three species.

Acknowledgment: This work and the new species name have been registered with ZooBank under urn:lsid:zoobank.org:pub:62CECB3F-D284-472D-A587-C88F44C89866 . NKN would like to thank the late Lady McNeice Yuen Ping, who has been extremely generous with her financial support, enabling the first author to visit various European museums to examine comparative materials. The French Merlion-Singapore Fellowship to NKN and TN as well as the MNHN Visiting Fellowships (2009-2013) to NKN are also acknowledged for financial support that allowed authors to travel to MNHN to check specimens. NKN acknowledges financial support from the Department of Biological Sciences, National University of Singapore, which allowed her to travel to Taiwan and the Smithsonian Institute, Washington D.C. This study was also supported by a grant from the Ministry of Science and Technology (MOST 105-2621-B-005- 002-MY3), Executive Yuan, Taiwan, to HTS. The authors are also grateful to Peter K.L. Ng for his encouragements and various help. This is a contribution from the Systematics and Ecology Laboratory, Department of Biological Sciences, and the Tropical Marine Science Institute, National University of Singapore. Authors acknowledge Peter K. L. Ng and Shane Ahyong, who greatly improved the manuscript.

Authors’ contributions: NKN performed the m o r p h o l o g i c a l d e s c r i p t i o n a n d d r a f t e d t h e manuscript. TN did field collections and drafted page 10 of 11

the manuscript. HTS performed the DNA analyses and wrote the discussion. All authors contributed to drafting and revising the manuscript. All authors read and approved the final manuscript.

Figures

Fig. 1. Helice epicure sp. nov. Paratype, male (26.4 × 30.1 mm) (RUMF-ZC-3069). (A) dorsal entire view; (B) cephalothorax, ventral view; (C) right chela, outer view.

Fig. 2. Left suborbital ridge of Helice epicure sp. nov. and H. formosensis Rathbun, 1931. (A) H. epicure sp. nov., holotype, male (25.3 × 30.7 mm) (RUMF-ZC-5009); (B) H. formosensis, male (27.0 × 31.4 mm) (NCHUZOOL).

Fig. 3. Helice epicure sp. nov. Holotype, male (25.3 × 30.7 mm) (RUMF-ZC-5009) (A-D), female (18.4 × 23.5 mm) (RUMF-ZC-5011) (E). (A) pleonal somites 3-6 and telson; (B) left G1, mesial view; (C) left G1, lateral view; (D) left G2, ventral view; (E) gonopore (= vulva). Scale bars: A = 5.0 mm, B-E = 1.0 mm.

Fig. 4. A Bayesian inference (BI) of species of the Helice/Chasmagnathus complex from Japan (including the Ryukyus), Korea, China, and Taiwan (including Penghu) based on cytochrome oxidase subunit I (COI) genes. Support values at the nodes represent the posterior probability for BI and the bootstrap values for maximum parsimony (MP).