Conchoecetes atlas, Naruse, 2019

Naruse, Tohru, 2019, Revision of the shell-carrying crab genus Conchoecetes Stimpson, 1858 (Crustacea: Brachyura: Dromiidae), Zootaxa 4706 (1), pp. 1-47 : 10-15

Conchoecetes atlas n. sp.

( Figs. 4 , 5 , 6B )

Conchoecetes artificiosus — Stimpson 1858: 78 ; 1907, 180, pl. XXI, fig. 5;— Rathbun 1910: 367 (part from Koh Samit);—Balss 1922: 110;— Sakai 1935: 34, text fig. 3; 1936: 42, pl. 8 fig. 2; 1965: 11, pl. 5, fig. 3; 1976: 26, pl. 6, fig. 2;— Dai & Yang 1991: 30, fig. 10, pl. 2, fig. 8;—Ng et al 2000: 156 (specimens from Honk Kong, Singapore and Thailand);— Ng et al 2001: 5 (list) (part);— Naruse et al 2014: 26, fig. 2a:— Ng et al, 2017: 24. [Not Conchoecetes artificiosus ( Fabricius, 1798].

Type. Philippines: ZRC 2019.1631 , holotype, male, 32.5 × 31.1 mm, Camiguin Island, Bohol Sea , 9º10’N, 124º43’E, taken in tangle net, depth unknown, coll. 22 Sep. 2015 , specimen purchased online and donated by C. McLay, Mar. 2017.

Material examined. Japan: BMNH 1904.10.11.21, male 21.7 × 21.5 mm, with shell, Inland Sea, Japan, coll. R. Gordon Smith; SUF Cat. No. 6136, male, 33.4 × 32.7 mm, with shell, Oh Shima, Japan; SUF Cat. No. 9161, male, 29.7 × 29.2 mm, Ohshima, Japan; SUF Cat. No. unknown, female 24.8 × 22.5 mm, Tosa Bay; NHMB-87551 (was ZMUC-CRU-10106), female 32.6 × 31.8 mm, exact collection site unknown; NHBM-87554 (was ZMUC- CRU-10109), male 27.5 × 25.3 mm, Misaki, Sagami Bay, Japan, coll, F. Doflein, 27 Aug. 1913; NSMT-Cr-8196, ovig. female 21.9 × 22.2 mm, exact collection site unknown, 15 Jun. 1982; RUMF-ZC-4705, male 16.8 × 16.4 mm, ovig. female 15.6 × 15.4 mm, female 14.3 × 14.2 mm, Yura, Sumoto, Awajishima Island, Japan, 50–60m, trawl, coll. J. Okuno, 21 Oct. 2009.

China: ZRC1999.0463 , 2 males 29.7 × 29.4 mm, 30.0 × 29.8 mm, Guangdong, Nanao Island , Qian Jiang Fish Port, coll. Y. Cai & N. K. Ng, 14 Nov. 1998 ; ZRC1999.0465 , female 26.0 × 25.0 mm, Guangdong, Nanao Island , Qian Jiang Fish Port, coll. Y. Cai & N. K. Ng, 12 Nov. 1999 .

Hong Kong: ZRC 1996.1885, male 16.9 × 15.8 mm, further details uncertain (see Ng et al. 2000: 156).

Taiwan: NHMB-87555 (was ZMUC-CRU-10110), male 28 × 27.5 mm, Formosa- Kana leu, 46–50 m, coll. & det. Skenson, 23 May 1897 ; ZRC 2019.1666 [ex NTOU1998.4 ], male 22.5 × 22.4 mm, Tainan, coll. Wu Shu-Ho (reported by Ahyong et al 2009: 32); RUMF-ZC-3005, 5 females, 29.9 × 28.3 mm, 31 × 30.8 mm, 31.4 × 30.8 mm, 31.8 × 30.4 mm, 34.1 × 32.6 mm, Kezailiao Fish Port , Kaohsiung, 150 m, 9 Jul. 2011 .

Cambodia: RUMF-ZC-1907, male 24.7 × 23.1 mm, Kampong Kandal Fish Port, Kampot City , 10º34’7.01”N, 104º143’33.21”E, coll. T. Naruse & D.C.J. Yeo, 27 Dec. 2010.

Thailand: ZRC 1999.0080 , 3 males 16.3 × 16.3 mm, 17.5 × 17.3 mm, 25.5 × 25.3 mm, female 20.7 × 21.0 mm, Ang Sila Fish Port, Gulf of Thailand , coll. P.K.L. Ng, Sep. 1998 ; ZRC1999.0445 , male 23.5 × 23.3 mm, ovig. female 23.7 × 23.0 mm, Chonburi, Gulf of Thailand , coll. P. Naiyanetr, 1996 ; ZRC2013.0201 , female 21.5 × 20.3 mm, Ang Sila Fish Port, Gulf of Thailand , 3 Dec. 2004 ; ZRC1997.0674 , ovig. female 26.9 × 26.0 mm, Gulf of Thailand , off Chonburi, coll. P. Naiyanetr, 1986 .

Singapore: NSMT-Cr-338, male 19.4 × 20 mm, 2 females 19.2 × 18.9 mm, 24.4 × 21.8 mm, South China Sea near Singapore, coll. Hee Huat, 16 Sep. 1983 (ex Takeda) .

Indonesia: ZMUC, male 8.0 × 8.0 mm, Amboina Bay , depth unknown, stone sand, dredged, coll. Th. Mortensen, 22 Feb. 1922 ; ZMUC, female 10.5 × 10.4 mm, Amboina Bay , depth unknown, stones, coll. Th. Mortensen, 23 Feb. 1922 ; ZMUC, juv. 5.3 × 5.4 mm, female 8.5 × 8.6 mm, Amboina Bay , depth unknown, stones, coll. Th. Mortensen, 23 Feb. 1922 ; ZMUC, 2 juv. 5.0 × 4.9 mm, 5.3 × 5.4 mm, Amboina Bay , depth unknown, stones, coll. Th. Mortensen, 25 Feb. 1922 ; ZMUC, 2 females 11.7 × 11.3 mm, 12.5 × 12.5 mm, stn 116, 5º57’S, 106º34’E, Java Sea , 22 m, Sigsbee Trawl, coll. Th. Mortensen, 7 Aug. 1922 ; ZRC2003.0644 , male 22.5 × 22.0 mm, female 23.6 × 23.6 mm, Jepara, Java Sea , 44 m, coll. D. L. Rahayu , RV Samundra , 14 Oct. 1976 .

Description. Carapace slightly wider than long, sub-pentagonal, surface noticeably convex, smooth except for frontal groove behind rostral teeth, cardiac area distinctly marked, weak, broad cervical groove, branchial groove narrower. Diagonal ridge behind branchial groove defines slightly concave triangular area filling posterolateral corner of carapace where sub-dorsal P5 lies. Rostral teeth triangular, subacute, median tooth at lower level, narrower, deflexed; supraorbital tooth small, no post-orbital tooth, sub-orbital tooth small, not visible dorsally. Anterolateral margin slightly sinuous bearing small tubercles, interrupted posterolaterally by cervical groove which is followed by strong shoulder-like anterolateral tooth. Behind this tooth carapace margin converges posteriorly, interrupted by branchial groove without forming distinct posterolateral tooth. Posterior carapace margin weakly concave. Subhepatic area mostly smooth, lower margin marked by row of small irregular granules which curve back towards prominent anterolateral tooth. Third maxillipeds operculate, crista dentata armed with 11 or 12 small stout teeth.

Cheliped carpus sparsely granulate, with pair of more or less equally prominent tubercles on outer distal margin of upper surface; propodus densely covered with small granules, fewer on superior face, inner face densely setose, pair of large hump-like tubercles at articulation with dactyl; fingers down-curved armed with 8 interlocking teeth, proximal superior face covered with small granules. P2 and P3 shorter than chelae, P2 longest, distal posterior margins of carpi and propodi with blunt projections, upper margins of long sharp dactyli fringed with longer setae, inner margins armed with many tiny adpressed spines. P4 and P5 shorter, P4 strongest, anterior margin of carpus without tubercles, dactylus strongly curved, talon-like to grasp hinge-line of bivalve shell; P5 shortest, sub-dorsal, flattened, dactylus short twisted.

Male telson triangular, bell-shaped, posterior margin convex, uropods well developed, visible externally, locking in front of tubercles on bases of P2. Margins of male and female pleon setose, and outer surface with strong broad central ridge. Female sternal sutures 7/8 end apart between P2 bases.

Colours. A dried crab from Camiguin I., Philippines has pale ground colour, brown setae, bright pink cheliped fingers ( Fig 6B ). Sakai (1965 & 1976) illustrated a specimen from Sagami Bay, Japan, showing dark brown ground colour with carapace grooves highlighted red-pink colour and cheliped fingers and some tubercles thereon similar.

Etymology. The specific name is derived from “Atlas”, the Greek Titan who held up the heavens, and an allusion to the fact that this crab carries a bivalve shell above its body, thereby defining its “visible world”. It is a noun used in apposition.

Remarks. Conchoecetes atlas n. sp. was first recorded in the literature as Conchoecetes artificiosus by Stimpson (1858: 78) and again by Stimpson (1907, 180, pl. 21, fig. 5). The illustration of the specimen of Cancer artificiosa by Herbst (1803: 54, pl. 58, fig 7) was rather stylised and only provided a generic figure, which lacked details that might be used to separate individual species (see Fig. 2B ). Hence, when Stimpson (1907) published his low quality photograph of a specimen from Hong Kong, subsequent authors such as Balss, T. Sakai ( Japan) and Rathbun ( Thailand) followed using his photograph to identify their material. The first specimen(s) of Conchoecetes from Japan were probably collected by the “Valdivia” Expedition in 1900 but not reported as such until after 1907, by Balss (1922). As new material came along Conchoecetes artificiosus s.l. became known as a species with considerable variation ( Lewinsohn 1984, 119).

Within the China-Japan-Taiwan-Philippine area the name Conchoecetes artificiosus s.l. was applied to material that we now separate into two species: Conchoecetes atlas n. sp. and Conchoecetes chanty n. sp. Below, we make a detailed comparison between them under the name of the latter species. Here we discuss regional variation within C. atlas n. sp. To facilitate comparison we limit the comparison to males. Specimens from the Philippines ( Figs 4 , 6B ), Taiwan ( Fig 5C ), China ( Fig 5B ) and Japan ( Fig 5A ) differ noticeably in the convexity of their carapace. Japanese specimens are almost flat while those from the Philippines are most convex. There is also variation in the development of teeth on the carapace anterolateral margin. The body shape of this species is sub-pentagonal with the anterolateral and posterolateral margins being approximately equal in length while the posterior margin (width) is about 20% shorter. At the widest point (CW) the distance is about 80% longer than either of the lateral margins. The widest point is marked by the anterolateral tooth preceded by a notch (part of the cervical groove) both of which vary in size and shape, the rostral and orbital areas also show variation in the size and shape of the lateral teeth and development of the supraorbital tooth. A distinctive feature of C. atlas n. sp. is the presence of two large distal tubercles on the outer distal margin on the upper surface of chela carpus which vary in elevation and bluntness. We treat specimens from all these areas as one species but future molecular data from new material may provide a different answer.

Conchoecetes atlas n. sp. is also sympatric with Conchoecetes pectenicola in the South China Sea and Indonesia. They can be distinguished primarily by C. atlas n. sp. having a distinct shoulder-like anterolateral tooth ( Fig 4 ) compared to a blunt lobe not preceded by a cervical notch in C. pectenicola ( Fig 20 ). Also they differ in the shape of the carapace: both are sub-pentagonal but in C. pectenicola the widest point is more anterior (i.e. shorter anterolateral margin) and the posterior carapace margin is relatively wider (60% of CW vs 45% of CW).

Habitat. Coastal muddy or sandy bottoms, most specimens collected from refuse landed at fishing ports so exact depth uncertain for many specimens. Recorded depth range is 15– 85 m.

Distribution. Japan, China, Hong Kong, Taiwan, Cambodia, Thailand, Philippines, Singapore and Java Sea Indonesia.

Figures

FIGURE 2. Conchoecetes artificiosus (Fabricius, 1798). NHMB-81740 (was ZMUC-CRU-3622), lectotype, female, 31.7 × 31.7 mm, Tranquebar, India, coll. I. K. Daldorff.A dorsal view (outer face right chela inset) (photograph by Peter Ng); B, dorsal view of another female 28.5 × 26.5 mm (ZMB HERBST 0819) (after Herbst 1803: pl. 58 fig. 7).

FIGURE 4. Conchoecetes atlas n. sp., ZRC 2019.1631, holotype, male, 32.5 × 31.1 mm, Camiguin Island, Bohol Sea, Philippines. A, dorsal view; B, frontal view; C, ventral view of anterior region.

FIGURE 5. Conchoecetes atlas n. sp., dorsal views. A, SUF Cat. No. 9161, male, 29.7 × 29.2 mm, Ohshima, Japan; B, ZRC1999.0463, male, 30.0 × 29.8 mm, Guangdong, Nanao Island, China; C, NHMB-87555 (was ZMUC-CRU-10110), male, 28 × 27.5 mm, Taiwan.

FIGURE 6. A, Conchoecetes chanty n. sp. showing fresh colours, female, 36.3 × 35.5 mm from East China Sea; B, Conchoecetes atlas n. sp., male, 30.5 × 29.0 mm, from Camiguin I., Philippines (photographs by Ondrej Radosta).

FIGURE 20. Conchoecetes pectenicola (Adams, in Belcher, 1848), NHMB-87556 (was ZMUC-CR-10111), ovig. female, 19.8 × 19.4 mm, exact origin uncertain, forwarded to Copenhagen Museum by Swedish Consul in Singapore, 4 Jun. 1903. A, dorsal view; B frontal view; C, right chela and anterolateral margin.