1 INTRODUCTION

Xanthidae MacLeay, 1838, is one of the most diverse families in the Brachyura and currently includes 15 subfamilies, 124 genera, and 639 species (Ng et al., 2008; Lai et al., 2011; Mendoza and Guinot, 2011; Mendoza and Manuel-Santos, 2012; Mendoza et al., 2012). They are common shallow water fauna worldwide especially in tropical reef habitats of Indo-West Pacific region, and are abundant in areas with rock, shell, or coral rubble substrates (Serène, 1984). Some members of this family are dominant taxa and may play a significant ecological role in reef food webs, such as Chlorodiellinae crabs, which were 37% of the crustaceans found in five reef-associated fish species guts in Moorea (Leray et al., 2012; Lasley et al., 2015). Recent systematic studies showed that Xanthidae is polyphyletic and most of the 15 subfamilies are also not monophyletic. The family clearly requires further systematic revision, and future studies will require greater taxon sampling and area coverage (Lai et al., 2011).

There are few systematic studies on the Xanthidae of Chinese waters, although they are frequently referred in surveys and studies of brachyuran species. Yang et al. (2008) provided a checklist of Brachyura from China seas, including 161 species of Xanthidae. Ng et al. (2017) provided a checklist of Brachyura from Taiwan Island, which contained 132 species of Xanthidae. To date 180 species from 61 genera and 11 subfamilies have been recorded from Chinese waters (Yang et al., 2008; Ng et al., 2017).

More systematic studies are necessary for Xanthidae from Chinese waters. In a recent collection, five new records of xanthid species were reported from Hainan Island, South China Sea. In this paper, their detailed diagnosis, photographs, line drawings, and taxonomic discussions are provided.

2 MATERIAL AND METHOD

All specimens were preserved in 70% Ethanol and deposited in the Marine Biological Museum, Chinese Academy of Sciences (MBMCAS) in Qingdao, China.

Specimens were observed by ZEISS Stemi 2000-c and ZEISS Stemi SV 11 Apo stereo microscope. Morphologies of G1 were observed by Nikon Eclipse Ci-L microscope. Photographs were taken by Canon EOS 6D camera with Canon EF 100-mm and Canon MP-E 65-mm lens.

Terminologies used for adult morphology follows that defined by Dana (1852) and Serène (1984). The following abbreviations were used in the text: CW (maximum carapace width); CL (median carapace length); G1 (first gonopod of male); st1–8 (thoracic sternites 1–8); P1–5 (pereopods 1–5); 1–2F (frontal regions 1–2); 1–4M (medial regions 1–4); 1–6L (antero-lateral regions 1–6); 1–3R (postero-lateral regions 1–3); 1–2P (posterior regions 1–2).

3 TAXONOMY

Family Xanthidae MacLeay, 1838

Subfamily Euxanthinae Alcock, 1898

Genus Hypocolpus Rathbun, 1897

Hypocolpus haanii Rathbun, 1909

Cancer (Xantho) granulatus Haan, 1837, 65, Pl.18, Fig. 3.

Hypocolpus haanii Rathbun, 1909: 114; Mendoza and Ng, 2010: 62, Figs. 2A, 3C, D.

Hypocolpus haani Sakai, 1939: 457, 458, Fig. 27, Pl. 89, Fig. 1.

Hypocolpus granulatus Guinot-Dumortier, 1960: 187, Pl.1,Fig. 5, Pl.2, Fig. 12, Pl.3, Pl.3, Fig. 18, Pl.6, Fig. 33, Pl.9, Figs. 52, 53; Sakai, 1976: 417, Text-fig. 220b, Pl.150, Fig. 4; Serène, 1984: 76, 79, Fig. 35.

Material examined

South China Sea: MBM286755, 1♂, Lingao Cape, Hainan, 15–30 m, Yunhao PAN coll., 20 August 2018; CW 45.27 mm, CL 34.23 mm.

Diagnosis: Carapace (Fig. 1a) transversely oval, breadth about 1.3 times the length; dorsal surface regions distinctly defined by wide, deep and smooth grooves; regions convex, covered with granules and interspersed with short setae, brush-like setae presenting on 1M, outer lobules of 2M, 3–5L, and 1P. Front produced, deflexed, divided into 2 lobes which touching each other on tips. Dorsal inner orbit raised, ventral inner orbital angle projecting. Subhepatic cavity (Figs. 1b, c, & 2a) reniform, inner brim blunt and outer brim sharp, inner surface smooth. Anterolateral border divided into 3 lobes, the first lobe forming the dorsal brim of the subhepatic cavity, the second lobe broad, and the third lobe triangular. Posterolateral border shorter than anterolateral border, distinctly concave. Lateral surface of carapace clothe with setae. Antennule situated transversely; orbital hiatus filled by basal antennal segment, flagellum small. Third maxilliped (Figs. 1c & 2b) completely covering buccal orifice, covered with granules; merus subquadrate, anterolateral angle slightly produced; ischium subrectangular; ischium and merus with a smooth groove respectively. Thoracic sternites (Fig. 1d) covered with dense and prominent granules; the groove between st1–2 and 3 deep, middle slightly convex backwards, st3 and st4 divided by a deep groove, the median line of st4 short and deep.

Chelipeds (Figs. 1e, f, & 2c) stout and symmetrical, subhepatic cavity exposed completely when they are folded, interspersed with short setae; merus with long setae on edges; carpus very stout, with granules and tubercles on the dorsal surface, inner angle armed with a prominent tooth pointing to the dorsal; palm with large warty granules on outer surface, interspersed with clavate setae; dorsal surface smooth, inner edge cristate; fingers deflexed slightly, dactylus with 2 rows longitudinal dorsal spiny granules, cutting edges of fingers with 5 teeth respectively; finger tips sharp, the tip of fixed finger inside when close.

Ambulatory legs (Fig. 1a) short; merus with setae on dorsal surface and edges, granules on anterior edge and posterior dorsal surface; carpus and propodus with spiny granules; dactylus with curving setae, tip claw-shaped.

Pleonal somites (Fig. 1d) 3–5 completely fused in male. G1 (Fig. 2d & e) slender, tip blunt, with little spines, armed with 7 subdistal setae: 5 long plumose setae, 1 shorter and slender non-plumose seta, and a stick-like truncated seta, may be a broken plumose seta.

Distribution: Hainan Island; Philippine Islands (Mendoza and Ng, 2010), Gulf of Siam (Rathbun, 1909), southeast coast of Japan (de Haan, 1833–1850; Sakai, 1939, 1976).

Type locality: Japan.

Remark: Hypocolpus haanii can be identified by its smooth, fusiform subhepatic cavity that does not have any depression, crests, or granules. The specimen from Hainan Island examined fits with previous descriptions (de Haan, 1833–1850; Sakai, 1939; Guinot-Dumortier, 1960), except there are 5 plumose setae in Guinot-Dumortier's line drawing (Guinot-Dumortier, 1960), while 7 intact or broken setae in our specimen, one of which is shorter and non-plumose. H. haanii is most related to H. rugosus (Henderson, 1893), on they have similar carapace regions (Guinot-Dumortier, 1960; Serène, 1984). H. rugosus can be identified by the ovoid subhepatic cavity with a marked depression at the exterior of emarginate edge, and eroded thorax and abdomen with hollow and depressions (Serène, 1984). The only species of Hypocolpus recorded from China Sea previously is Hypocolpus abbotti (Rathbun, 1894), which has a more setose carapace and a subhepatic cavity with 2 longitudinal crests.

Subfamily Liomerinae Sakai, 1976

Genus Neoliomera Odhner, 1925

Neoliomera variolosa (Milne-Edwards, 1873)

Liomera variolosa A. Milne-Edwards, 1873: 255, Pl.1, Fig. 5.

Neoliomera variolosa Odhner, 1925: 30, Pl.2, Fig. 10; Tweedie, 1949: 89; Poupin, 1996: 41.

Material examined

South China Sea: MBM286756, 1♂, Moon Bay, Wenchang, Hainan, 15–30 m, Yunhao PAN coll., 4 December 2018; CW 27.75 mm, CL 17.85 mm.

Diagnosis: Carapace (Figs. 3a & 4a) transversely oval, breadth about 1.6 times the length; regions well-defined anteriorly while vague posteriorly; dorsal surface covered with rounded granules, granules on sides larger then middle, interspersed with short setae and long yellow setae. Anterolateral border (Figs. 3e & 4a) divided into 4 blunt lobes by deep grooves, the first lobe connecting outer orbit, the second lobe forming a small tubercle, hepatic region protruding forward and separated from the first two anterior lobes by a very deep and distinct groove; front deflexed, divided into 2 lobes. Posterolateral border about equal to anterolateral border. Antennule situated transversely; orbital hiatus filled by antennal flagellum. Third maxilliped (Fig. 3c) completely covering buccal orifice; merus subquadrate, anterolateral angle slightly produced; ischium subrectangular, with a smooth groove. Thoracic sternites (Fig. 3d) smooth, interspersed with pits; the groove between st1–2 and 3 straight, the median line of st4 short and shallow.

Chelipeds (Figs. 3f & 4b) symmetrical; merus covered with flat granules; dorsal surface of carpus, dorsal and outer surface of palm covered with granules and setae similar to carapace; palm stout and short, outer surface covered with large granules, inner and ventral surface smooth; fingers short and broad, dactylus with 2 longitudinal dorsal grooves, cutting surface of fingers with 2 rows of flat teeth; finger tips blunt and concave.

Ambulatory legs (Figs. 3a, b, & 4c) short and strong, clothed with granules, long yellow setae on edges of ambulatory legs. Dactylus with yellow setae, tip claw-shaped.

Pleonal somites (Fig. 3d) 3–5 completely fused in male. G1 (Fig. 4d & e) slender, with about 15 long plumose subdistal setae, 7 stick-like setae on the margin of the distal tip, should be residual proximal parts of truncated long plumose setae; apical lobe acute, slightly upturned.

Distribution: Hainan Island; Aur Island (Tweedie, 1949), Upolu Island (Milne-Edwards, 1873), Moorea Island (Poupin, 1996).

Type locality: Upolu Island.

Remark: N. variolosa was originally described by Milne-Edwards (1873) from Upolu Island with a brief description and line drawing. Odhner (1925) provided a more detailed description of carapace and a more accurate drawing for this species. In addition to the type location, Poupin (1996) listed this species in French Polynesian fauna, distributed in Moorea Island, and Tweedie (1949) reported it from Aur Island based on 4 males and 2 females collected. The specimen from Hainan Island examined fit well with previous descriptions and line drawings (Milne-Edwards, 1873; Odhner, 1925). Color photograph and a description of G1 are provided here for the first time.

Neoliomera variolosa is most related to N. sabaea (Nobili, 1906) morphologically on both of them have a red and setose appearance (Nobili, 1906; Forest and Guinot, 1961; Galil and Vannini, 1990). N. variolosa can be identified by the deep and distinct groove in front of hepatic region, shallower and narrower carapace grooves, and the G1 with an upturned apical lobe, which is straight in N. sabaea (Forest and Guinot, 1961).

Subfamily Xanthinae MacLeay, 1838

Genus Leptodius Milne-Edwards, 1863

Leptodius davaoensis Ward, 1941

Leptodius davaoensis Ward, 1941: 10, FigS. 13, 14; Lee, 2012: 245–250, Figs. 173–175.

Material examined

South China Sea: MBM286757, 1♂, Fengjiawan, Wenchang, Hainan, Junlong ZHANG coll., 15 November 2016; MBM286758, 2♀, Xiaodonghai, Hainan, Wei JIANG coll., 23 March 2008 MBM286759, 1♂, Xiaodonghai, Hainan, Wei JIANG coll., 25 December 2007; MBM282433, HBRC-3293, 3♂3♀, Xiaodonghai, Hainan, 24 December 2007; in MBM163925, 90C-887, Linchang, Hainan, 1 December 1990 in MBM163922, 90C-472, 3♂, Luhuitou, Hainan, 21 November 1990; MBM286760, 92C-460, 5♂4♀, Luhuitou, Sanya, Hainan, 17 March 1992; MBM286765, 1♂, Luhuitou, Sanya, Hainan, Yunhao PAN and Fei MENG coll., 6 July 2020; CW 9.91–19.34 mm, CL 6.56–12.54 mm.

Diagnosis: Carapace (Figs. 5a & 6a) hexagonal, breadth about 1.5 times the length; anterior 2/3 of dorsal surface well-defined; regions granulated, covered with fine granules, sporadic long setae on anterior margin of regions. Front (Figs. 5d & 6a) deflexed and produced, divided into 2 lobes by a narrow Y-shape notch. Dorsal orbital edge with double cracks. Anterolateral border (Figs. 5d & 6a) armed with 4 triangular teeth except outer orbital angle, first small, with an appendant little tooth beneath, second and third large, last tooth small, following by a crest or a bump, this bump producing a sharp fifth tooth in some large male individuals. Posterolateral border shorter than anterolateral border, somewhat concave; lateral surface of carapace with bushy setae that visible from dorsal. Antennule situated transversely; orbital hiatus filled by antennal flagellum. Third maxilliped (Fig. 5b) completely covering buccal orifice; merus subquadrate, granulated, anterolateral angle produced; ischium subrectangular, with a smooth groove. Thoracic sternites (Fig. 5c) smooth; the groove between st1–2 and 3 straight, the median line of st4 long and shallow.

Chelipeds (Figs. 5e, f, 6b, & c) unequal; merus with bushy setae on edges; carpus armed with a tooth on inner angle, dorsal surface granulated with tubercles, inner surface with long setae; palm strong, prolonged and granulated, dorso-external surface rugose; dactylus with 2 longitudinal dorsal grooves, cutting edges with 2–3 triangular teeth, dactylus meeting fixed finger only at tips when closed; finger tips spoon-shaped with a tuft of setae.

Ambulatory legs (Fig. 5a) granular; edges with long setae; dactylus with little spines and setae, tip claw-shaped.

Pleonal somites (Fig. 5c) 3–5 completely fused in male. G1 (Fig. 6d & e) slender and curving, subdistal portion with 6 strong spines curving to dorsal, apical lobe prolonged, ventral edge armed with 9 tongue-shaped extensions.

Living color is shown in Fig. 7.

Distribution: Hainan Island; Singapore: Tioman Island, Singapore Strait, Malaysia: Pisang Island, Indonesia: West Lombok Island, Micronesia: Kosrae Island, Philippines: Gulf of Davao (Ward, 1941; Lee, 2012).

Type locality: Gulf of Davao.

Remark: L. davaoensis was originally described by Ward (1941) from Gulf of Davao. Lee (2012) gave a redescription based on specimens collected from Indo-West Pacific. The present specimens generally fit with the previous descriptions (Ward, 1941; Lee, 2012), but slightly differ from the figures (Ward, 1941:Figs. 13, 14; Lee, 2012: Fig. 174) by the following characters: 1) the front more produced in present specimens, while only slightly produced and with more distinct granules in the holotype; 2) the anterolateral tooth broader in present specimens, while it more produced and narrower in the holotype. Moreover, the number of tongue-shaped extensions of G1 is 9 in the largest male specimen, while the number is 10–12 in Lee's description.

Leptodius davaoensis is most related to L. australis, and the differences are discussed under the remarks of L. australis. L. davaoensis is also similar with L. sanguineus (Milne Edwards, 1834) for having a produced bump following the last anterolateral tooth and forming a fifth tooth on large specimens (Fig. 5d). However, based on present observation, L. sanguineus differs from L. davaoensis by having a less produced front, wider carapace grooves, and the G1 with a much shorter apical lobe (Serène, 1984: 180, Fig. 108, Pl.26, Fig.B).

Takeda (1980) suggested that the holotype of L. davaoensis is conspecific with L. leptodon Forest and Guinot, 1961. Ng et al. (2008) listed L. leptodon as a junior synonym of L. davaoensis. Lee (2012) suggested L. davaoensis as a distinct species from L. leptodon. In fact, the present specimens are distinct from the description of L. leptodon by Forest and Guinot (1961) in the following characters: 1) the apical lobe of G1 curving to outside and with 9 tongue-shaped extensions, while L. leptodon having more slender apical lobe of the G1 curving to inside and with 14 tongue-shaped extensions; 2) the anterolateral teeth of carapace triangular, while the first anterolateral teeth rounded and the second truncated in L. leptodon.

Undoubtedly, the taxonomy of Leptodius is not satisfactorily resolved presently (Forest and Guinot, 1961; Serène, 1984; Lee, 2012; Lee et al., 2013). G1 is probably a better morphological character for the diagnosis. A revision of Leptodius is needed.

Leptodius australis Ward, 1936

Leptodius australis Ward, 1936: 6, Pl.2, Figs. 7–9; Lee, 2012: 240–244, Figs. 170–172.

Material examined

South China Sea: MBM286762, 3♂, Xiaodonghai, Hainan, Wei JIANG coll., 23 March 2008 MBM286763, 2♂1♀, Xiaodonghai, Hainan, Wei JIANG coll., 25 December 2007; MBM282511, 2♂, Wei JIANG coll., 23 March 2008 in MBM163879, 92C-521, 3♂3♀, Ximao Island, Sanya, Hainan, 20 March 1992; in MBM163881, 90C-197, 1♀, Xiaodonghai, Hainan, 11 November 1990; in MBM163872, 90C-405, 1♂1♀, Luhuitou, Sanya, Hainan, 13 November 1990; MBM286761, 92C-460, 6♂2♀, Luhuitou, Sanya, Hainan, 17 March 1992; CW 5.51–17.84 mm, CL 3.67–10.95 mm.

Diagnosis: Carapace (Figs. 8a & 9a) transversely oval, breadth about 1.6 times the length; anterior 2/3 of dorsal surface well-defined; regions covered with fine flat granules; partition groove with sporadic long setae. Front (Figs. 8d & 9a) deflexed, not very produced, divided into 2 lobes by a wide V-shape notch. Dorsal orbital edge with double cracks. Anterolateral border (Figs. 8d & 9a) armed with 4 teeth except outer orbital angle, first tooth small, with an appendant little tooth beneath, second and third tooth broad, last tooth small and distinct. Posterolateral border about equal to anterolateral border, somewhat concave. Lateral surface of carapace with bushy setae that visible from dorsal. Antennule situated transversely; orbital hiatus filled by antennal flagellum. Third maxilliped (Fig. 8b) completely covering buccal orifice; merus subquadrate, granulated, anterolateral angle produced; ischium subrectangula. Thoracic sternites (Fig. 8c) smooth; the groove between st1–2 and 3 straight, the median line of st4 long and shallow.

Chelipeds (Figs. 8e, f, 9b, & c) unequal; merus with bushy setae on edges; carpus armed with a tooth on inner angle, dorsal surface with irregular areoles, inner surface with long setae; palm stout and granular, dorso-external surface rugose; dactylus with 2 longitudinal dorsal grooves, cutting edges with 2–4 triangular teeth, dactylus meeting fixed finger only at tips when closed; finger tips spoon-shaped with a tuft of setae.

Ambulatory legs (Fig. 8a) granular, edges with long setae; dactylus with little spines and setae, tip claw-shaped.

Pleonal somites (Fig. 8c) 3–5 completely fused in male. G1 (Fig. 9d & e) slender and curving, subdistal portion with 8 strong spines curving to dorsal, apical lobe prolonged, ventral edge armed with 8 tongue-shaped extensions.

Living color is shown in Fig. 10.

Distribution: Hainan Island; Philippine Islands (Lee, 2012), Australia (Ward, 1936).

Type locality: Queensland.

Remark: The present specimens fit with the previous descriptions (Ward, 1936; Lee, 2012). L. australis is most similar to L. davaoensis for the hirsute appearance and having the triangular anterolateral border teeth. Based on the present material, L. australis differs from L. davaoensis by: the not produced front and having a wider V-shape middle notch; the apical lobe of G1 with 8 extensions, and shorter and more straight than that in L.davaoensis.

Genus Xanthias Rathbun, 1897

Xanthias joanneae Mendoza, 2013

Xanthias joanneae Mendoza, 2013: 375,Figs. 1–4.

Material examined

South China Sea: MBM286764, 1♂, Hainan, 9–10 m, Junlong ZHANG coll., 21 November 2016. CW 8.34 mm, CL 5.48 mm, front width 2.65 mm, P5 merus width 1.13/1.12 mm; MBM163770, 1♀, Yalong Bay, Hainan, 20 November 1990. CW 7.45 mm, CL 4.72 mm, P5 merus width 0.92/0.95 mm.

Diagnosis: Carapace (Figs. 11a & 12a) transversely oval, breadth about 1.5 times the length, with 30–32 ocelli arranged symmetrical; dorsal surface well-defined by narrow but distinct grooves, regions smooth. Front (Figs. 11d & 12a) double-lobes, rounded and broad. Orbital region broad, dorsal edge with 2 fissures. Anterolateral border (Figs. 11d & 12a) armed with 4 rounded tooth include outer orbital angle, separated from each other by V-shape notches. Posterolateral border straight, longer than anterolateral border. Antennule situated transversely; orbital hiatus filled by antennal flagellum. Third maxilliped (Fig. 11b) completely covering buccal orifice; merus subquadrate; ischium subrectangular; merus and ischium with a large ocellus respectively. Thoracic sternites (Fig. 11c) smooth; the groove between st1–2 and 3 nearly straight, the median line of st4 long and shallow; st5–st7 with a pair of ocelli on margin respectively.

Chelipeds (Figs. 11e, f, & 12b) equal and finely granular; merus with setae on edges; carpus armed with a blunt tooth on inner angle; palm smooth except a shallow longitudinal groove on dorso-external surface; fingers black brown, the color of fixed finger extending to palm inner and outer in male; cutting edges with 5 triangular teeth, staggered when close, only little gap proximal; fixed finger with 2 carinae on outer surface; finger tips sharp, concave.

Ambulatory legs (Figs. 11a & 12c) smooth with ocelli on dorsal surface, merus flattened with a sharp anterior edge; dactylus with setae, tip claw-shaped.

Pleonal somites (Fig. 11c) 3–5 completely fused in male; ab1–3 with broken ocelli marginal and central, ab4–6 with a intact ocelli respectively, telson proximal broaden, with an incomplete ocellus. G1 (Fig. 12d & e) stout, with long plumose subdistal setae, apical lobe acute.

Distribution: Hainan Island; Philippines: Bohol Sea (Mendoza, 2013).

Type locality: Bohol Sea.

Remark: Up to now, there are 2 ocellated Xanthias species: Xanthias maculatus T. Sakai, 1961 and Xanthias joanneae Mendoza, 2013. Sakai (1961) described X. maculatus from Japan originally. Serène (1984) reported 4 related specimens from Kenya with similar color and ocelli, but they still have noticeable difference morphologically (Serène, 1984; Mendoza, 2013). He attributed those specimens and a specimen from Vietnam to Xanthias aff. maculatus and suggest these variations may be intraspecific depending the locality. Mendoza (2013) defined related specimens of Philippines to a new species X. joanneae. Diagnosis of X. joanneae and X. maculatus has been discussed (Mendoza, 2013). Later, Poupin et al. (2018) reported 5 specimens from Mayotte, which have intermediate characters between X. maculatus and X. joanneae, and he attributed those specimens to Xanthias maculatus sensu lato and suggested that a revision is needed to figure out whether it is a single species, with regional variations or there are more than 2 species must be considered in the 'ocellated'Xanthias.

Specimens from Hainan Island examined here also have intermediate characters between X. maculatus and X. joanneae, it's morphology fit with the description of X. joanneae by Mendoza (2013), except: 1) although the specimens has faded, the number of ocelli on dorsal surface of carapace can still be judged to be around 30 depending on the residual pigment (at least 40 in X. joanneae and about 14 in X. maculatus); 2) the ratio of the width of the P5 merus to carapace length=0.205 in the male specimen, 0.195–0.201 in the female specimen (0.22 in X. joanneae and 0.17 in X. maculatus); 3) carapace regions well defined, especially 2M, 3M (not well defined in X. joanneae and well defined in X. maculatus); 4) anterolateral borders tooth separated by narrow, V-shaped notches, first two tooth rounded while last two tooth with acute apices. (anterolateral tooth with more rounded apices, closer together, separated by narrow, V-shaped notches in X. joanneae and more acute apices, farther apart, separated by wide troughs in X. maculatus).

4 CONCLUSION

Five species of Xanthidae, H. haanii, N. variolosa, L. australis, L. davaoensis, and X. joanneae, have been reported from China for the first time. Based on observation and comparing, morphological characters of H. haanii, N. variolosa, and L. australis from Hainan Island are consistent with previous descriptions. Specimens of X. joanneae have intermediate characters between X. maculatus and X. joanneae. Its morphology is similar to the description of Mendoza (2013) excepting for some slight differences. Specimens of L. davaoensis are distinct from previous descriptions of L. leptodon, which once thought to be a junior synonym of the former. It is also slightly different with figures of the holotype of L. davaoensis, mainly on the morphology of carapace. Further comparison may help to clarify whether these differences are intraspecific or interspecific.

5 DATA AVAILABILITY STATEMENT

The data that support the findings of this study are available from the corresponding author upon reasonable request.

6 ACKNOWLEDGMENT

The authors are thankful to Junlong ZHANG, Yunhao PAN, and Fei MENG for their significant help in collecting materials. We also thank Xu ZHANG and Fei MENG for providing color photographs of living crabs used in this paper.