Conchoecetes pectenicola (Adams, in Belcher, 1848)

Naruse, Tohru, 2019, Revision of the shell-carrying crab genus Conchoecetes Stimpson, 1858 (Crustacea: Brachyura: Dromiidae), Zootaxa 4706 (1), pp. 1-47 : 34-35

Conchoecetes pectenicola (Adams, in Belcher, 1848)

( Figs. 19–21 )

Caphyra pectenicola Adams, in Belcher, 1848: 315 ;— White 1847: 54;— Wood 1867: 225, unnumbered fig.;— Hunter & Morris 1898: 4126;—Ng et al. 2008: 148 (incertae sedis)

Conchoecetes artificiosus —Ng et al. 2000: 156 (specimen from Thailand listed under Vietnam). [Not Conchoecetes artificiosus ( Fabricius, 1798) ].

Type: BMNH 44.106 , holotype, ovig. female 6.2 × 6.2, chelae missing, dry collection, Sunda Strait , Java, 24 m, carrying bivalve shell Mimachlamys senatoria (Gmelin, 1791) , coll. Capt. E. Belcher, ca. 13 Jun. 1843 .

Material examined. Gulf of Thailand: NHMB-87553 (was ZMUC-CR-10108), female 17.1 × 17.5 mm, male 21.5 × 21.9 mm, Siam Expedition , 32 km SE of Koh Samit, 25 m, sand, mud, dredge, coll. Th. Mortensen, 2 Feb , 1900; ZRC 1969.10.4.3, ovig. female 12.8 × 12.9 mm, off Cape Cambodia , 8º10’N, 104º35’E, 25–30 m, coll. R. Serène, 22 Sep. 1969 ; ZRC2008.1052 , male 16.2 × 15.9 mm, female 23.4 × 23.0 mm, ovig. female 16.2 × 16.0 mm, Ang Sila Fish Port, 21 Nov. 2003 ; ZRC2011.0164 , ovig. female 21.0 × 20.7 mm, Pattani Fish Port, 2003 .

Singapore: NHMB-87556 (was ZMUC-CR-10111), shallow water, ovig. female 19.8 × 19.4 mm carrying a bivalve shell, coll. Sven Gad (forwarded to Copenhagen Museum by Swedish Consul in Singapore, 4 Jun. 1903); ZRC1984.6309 , male17.3 × 16.9 mm, South China Sea near Singapore, coll. Hee Huat 27 Sep. 1983 .

Indonesia: ZMUC, 2 ovig. females 6.4 × 6.9 mm, 7.9 × 7.7 mm, stn 106, 5º60’S, 106º16’E, Java Sea , 32m, sand, coll. Th. Mortensen, 5 Aug. 1922 ; ZMUC, ovig. female 6.7 × 6.8 mm, Makassar Strait , 35 m, sand, dredge, coll. Th. Mortensen, 29 Jun. 1922 .

Description. Carapace about as wide as long, sub-pentagonal, flattened, surface smooth under fine soft tomentum, regions defined by shallow cervical, cardiac and branchial grooves. Rostrum tridentate, teeth similar length, median tooth narrower, slightly deflexed, set at lower level; margins finely granulate, supraorbital tooth small, blunt, similar suborbital tooth obscured below. Anterolateral carapace margin begins at supraorbital margin, gently convex, nonstructured and adorned with 9 or 10 small granules until meeting cervical groove behind which is a blunt lobe marking widest point. Posteriorly margin narrows towards branchial groove weakly marked without tooth; posterior carapace margin weakly concave. Subhepatic area not visible dorsally, sparsely setose and granulate.

Female sternal sutures 7/8 end apart between bases of P2 on scroll-like elevated structures.

Third maxilliped operculate, crista dentata of 9 to 10 corneous teeth.

Chela carpus minutely granulate, 2 large distal conical tubercles on outer surface; propodus granular, granules on outer face blunt, some larger ones tend to be arranged in 3 parallel rows, dorsal face has 2 unequal conical distal tubercles at base of dactylus; fingers covered in granules, armed with 9 or 10 interlocking white teeth. P2 and P3 longer than chelae, carpi have posterior corner of distal margin produced as blunt white lobe, dactyli dorsal margin fringed with 2 rows of longer stiff setae, otherwise covered in soft short tomentum; inner margins of dactyli armed with approximately twenty tiny adpressed, spines directed distally. P4 shorter much stronger than P2 and P3, finely granular, carpus without prominent marginal tubercles; dactylus talon-like curved proximally over-reaching strong quadrangular propodal projection, used to grasp bivalve camouflage. P5 sub-dorsal, shortest, barely reaching branchial groove, flattened, dactylus reduced, curved, non-prehensile.

Pleon of six free somites in both sexes, fringed with long setae, telson triangular, posterior margin convex, uropods well developed visible externally.

Remarks. The type specimen of this species, from the Sunda Straits, Java, was described as a portunid “ Caphyra pectenicola ” but Adams (in Belcher 1848: 315) said that it carried a “ Pecten ” shell in a manner reminiscent of dromiids. Later Wood (1867: 225, unnumbered fig.) illustrated Adams’ specimen in a stylized fashion and suggested that it might be some kind of pinnotherid. Adam’s name “ Caphyra pectenicola ” remained unused until we recently realized that it was very likely a species of Conchoecetes Stimpson, 1858 . Examination of Adams’ specimen in the dry collection at the NHM confirmed that this was the case. We reproduce here both Woods’ drawing ( Fig. 19B ) and a photograph of the type specimen ( Fig. 19A ).

The unusual thing about the type is that it is a small female (6.2 x 6.2 mm) which is ovigerous. Being in a very fragile state and covered in fine setae, the specimen is not amenable to close examination. It is intact except for missing chelipeds. The carapace is flat, sub-pentagonal in shape with cervical and branchial grooves evident under the setae. The anterolateral margin is shorter than the posterolateral margin. The P2 and P3 are long and largely without ornamentation and the dactyli are long and tapering to a sharp tip.

In the ZRC collection there is a female (ZRC 1969.10.4.3) collected off Cape Cambodia, 8º10’N, 104º35’E, 25–30 m, by Raoul Serène, 22 Sep. 1969, which is 12.8 x 12.9 mm and agrees with all of the details that we can discern from the type. In addition it is also ovigerous at a size much smaller than normally found in females of C. atlas n. sp. with which it has some resemblance. We also have other Southeast Asian material from the Gulf of Thailand and the South China Sea, in the vicinity of Singapore which are the same as Serène’s specimen. We are confident that these specimens can also be identified as Conchoecetes pectenicola . This species reaches maturity at a small size around 6 mm CW, similar to C. andamanicus . The species of Conchoecetes normally mature at around three times this size (see Table 1 ).

Figures

FIGURE 19. Conchoecetes pectenicola (Adams, in Belcher, 1848), (A, B) BMNH 44.106, holotype, dried ovigerous female, 6.2 × 6.2 mm, Sunda Strait, Java; (C–E) ZRC 1969.10.4.3, ovig. female, 12.8 × 12.9 mm, Gulf of Thailand. A, dorsal view (scale in mm only applies to A, photograph by Harry Taylor); B, drawing of holotype from Wood (1867: 225); C, dorsal view; D, frontal view; E, right P4 carpus, propodus and dactylus.

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.

FIGURE 21. 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; carrying bivalve shell (Mimachlamys senatoria (Gmelin, 1791). A, ventral view; B, frontal view.