Conchoecetes conchifera (Haswell, 1882)

Naruse, Tohru, 2019, Revision of the shell-carrying crab genus Conchoecetes Stimpson, 1858 (Crustacea: Brachyura: Dromiidae), Zootaxa 4706 (1), pp. 1-47 : 21-26

Conchoecetes conchifera (Haswell, 1882)

( Figs. 11–13 )

Dromia conchifera Haswell 1882a: 757 ; 1882b: 141, pl. 3 fig. 4.

Conchoecetes artificiosus — McNeill, 1923: 245 , 1 unnumbered figure;— Campbell & Stephenson 1970: 243;—Davie 2002: 159;— Jones & Morgan 2002: 136, unnumbered photo;— McLay & Hosie 2012: 187, fig. 2 A–D. [Not Conchoecetes artificiosus ( Fabricius, 1798) ].

Types. Australia: AM-P3895, lectotype (herein designated), female, 19.9 × 20.8 mm, paralectotype (herein designated), female, 15.9 × 16.7 mm 15.9 × 16.7 mm. Haswell (1882) recorded this species from at least two localities, Port Denison and Port Molle , both are probably near Bowen , Queensland .

Material examined. Australia: WAM-58-83, male 23.6 × 23.7 mm, Shark Bay, FV ‘Peron’, 10 Mar. 1965; WAM-112-83, male 23.7 × 23.8 mm; female ovig. 30.3 × 30.7 mm, 18 m, NE Malus Is., Dampier Archipelago, 31 May 1960; QM-W16118, female 5.5 × 6.2 mm, 19º59.05’S, Northwest Shelf, 117º51.4’E, 42 m, 18 Feb. 1983; QM- W16140, male 6.2 × 6.3 mm, female 11.5 × 11.6 mm, Northwest Shelf, 19º56.8’S, 117º53.5’E, 44m, 25 Jun. 1983; QM-W16142, female 4.8 × 4.5 mm, Northwest Shelf, 19º56.8’, 117º53.4E, 42 m, 22 Apr. 1983; QM-W16143, male 10.2 × 10.3 mm, Northwest Shelf, 19º29.9’S, 118º52.0’E, 38–39 m, 26 Apr. 1983; QM-W16156, male 12.5 × 12.5 mm, Northwest Shelf, 19º57.9’S, 117º49.3’E, 40 m, CSIRO “Soela”, 26 Jun. 1983; QM-W16161 male 9.0 × 9.4 mm, Northwest Shelf, 19º59.1’S, 117º49.0’E, 43 n, 25 Jun. 1983; QM-W16166 male 12.2 × 12.5 mm, Northwest Shelf, 19º29.6’S, 118º52.6’E, CSIRO Soela, 40– 39 m, 28 Jun. 1983; QM-W16169 female 8,3 × 8.5 mm, Northwest Shelf, CSIRO Soela, 19º58.5’S, 117º49’E, 42 m, 26 Jun. 1983; QM-W16173 male 9.4 × 9.5 mm, Northwest Shelf, 19º03.8’S, 119º3.5’E, 83 m, 29 Jun 1983; QM-W16178, 2 males 7.0 × 7.1 mm, 10.1 × 10.4 mm, female 10.7 × 10.8 mm, Northwest Shelf, 19º28.4’S, 118º55.2’E, 39 m, trawled CSIRO, RV Soela, 31 Aug. 1983; QM-W16198 male 9.6 × 9.7 mm, Northwest Shelf 50383, D35, CSIRO “Soela”, 1983; WAM C14481, male 11.9 × 12.5 mm, Abbot Point south of Townsville; WAM C14688, male 16.5 × 17.0 mm, Cockburn Sound, land side Garden Island; WAM C15525, male 19.0 × 19.8 mm, female 16.9 × 16.8 mm, off Anchorage Bay, Rosemary Island, Dampier Archipelago; WAM C 17155, female 19.6 × 20.0 mm, 60 n-miles NW of Cape Leveque; WAM C26222, male 13.5 × 13.7 mm (accompanying shell is Cardita marmorea Reeve, 1843 (Carditidae) , Dampier Archipelago, Cape Legendre, 36– 33m, coarse muddy sand and limestone rocks, gorgonians, sponges, 20°21.69’S, 116°52.40’E to 20°21.23’S, 116°52.36’E, 14 Jul. 1999; WAM C26229, male 13.4 × 13.9 mm, Dampier Archipelago, NW Point of Goodwyn, Is, 37– 36m, muddy sand, rubble, rocks, gorgonians, 20°29.31’S, 116°25.18’E– 20°29.62’S, 116°25.44’E, 21 Jul. 1999, collected by S. Slack-Smith & M. Hewitt; WAM-C26231, male 11.0 × 11.4 mm, DA2/99/56, Roly Rock, Dampier Arch., 20º30.1’S, 116º28.27’E, 21 Jul. 1999, collected by S. Slack-Smith & M. Hewitt; Colin L. McLay Collection, Moreton Bay, male 19.4 × 20.2 mm, Queensland, 5 m, 29 Dec. 1977; WAM-C51227, male, 19.7 × 20.2 mm, Barrow Island, 20°48’7.26”S, 115°30’27.42”E, 20 m, 1 May 2012.

Description. Carapace as wide as long, covered in fine soft tomentum, gently convex; cervical, branchial and cardiac grooves clearly marked. Rostrum tridentate, margins granulate, projecting strongly anteriorly, median tooth much shorter, deflexed. Supraorbital tooth large, blunt, no post-orbital tooth; infra-orbital margin with small blunt tooth, not visible dorsally. Anterolateral margin distinct, simple, no hepatic notch, adorned with small granules, continuing from post-orbital corner, slightly convex to blunt anterolateral corner marked by swelling rather than tooth following cervical groove, then margin convergent towards small blunt lobe following branchial groove. Subhepatic area below anterolateral margin mostly smooth except for few very small granules, not visible dorsally. Posterolateral margin convergent towards posterior corner, posterior carapace margin concave.

Third maxilliped operculiform, crista dentata with 9 or 10 small teeth.

Chela carpus in male has row of 4 or 5 granules on inner dorsal margin otherwise covered in smaller granules and with two strong distal tubercles at articulation with propodus which is also covered in granules. Dactylus densely covered with small granules, fingers gaping slightly with 7 or 8 interlocking teeth. Female chela less granulate.

P2 and P3 not armed with granules margins mostly smooth, dactyli bearing 2 or 3 rows of setae dorsally, inner margins of both have ~20 tiny adpressed scales. Shell-carrying P4 talon edges fringed with setae, stout, curved just over-reaching proximal propodal projection, but not exceeding carpus-propodus joint. P5 flattened sub-dorsal, margins without granules, dactyl short angled distally. P2 coxae, with slightly raised open slits rather than scrolls as in other species.

Male telson narrowly triangular, posterior margin convex, uropods visible externally locking in front of tubercles on coxae of P2. Female telson same but without pleon locking mechanism. Female 7/8 sutures end apart between P2 bases.

Habitat. Coarse muddy sand and limestone rocks, rubble, broken shell, gorgonians, and sponges. Depth 5– 83 m. Campbell & Stephenson (1970) give detailed data about the distribution of C. conchifera in Moreton Bay , Queensland.

Distribution. Endemic to Australian tropical coasts.

Remarks. Haswell (1882a) described Dromia conchifera from two specimens collected from 10–25 m near Bowen, Queensland. He commented that this species had “the curious habit of protecting itself with the valve of a lamellibranch, which it holds tight over its back by means of unusually powerful and specially adapted fourth pair of ambulatory legs” ( Haswell 1882a: 757). No mention is made of Dromia artificiosa Fabricius, 1798 , or the new genus Conchoecetes Stimpson, 1858 . Perhaps this was an oversight, but it is curious that he did not put his new species in Conchoecetes Stimpson, 1858 because he commented about the limbs adapted for shell-carrying.

It is also puzzling why Henderson (1893) concluded that Dromia conchifera Haswell, 1882 , was a synonym of Conchoecetes artificiosus . Henderson briefly describes some features of the carapace: “The carapace is flattened, and smooth under the pubescence, except towards the lateral margins where a few granules occur; the whole under surface is finely granulated.

The amount of granulation on the palm of the chelipeds varies in different individuals; the granules are polished and are sometimes arranged in lines.“ These features do not agree with the lectotype of Dromia artificiosa Fabricius, 1798 , however they are closer to Conchoecetes intermedius Lewinsohn, 1984 . One of us (CLM) has seen Haswell’s specimens in the Australia Museum, and they are very different from Fabricius’ lectotype of C. artificiosus . Henderson’s decision seems to be based on his comparison of BMNH Museum specimens from Madras with specimens from Moreton Bay, Australia. He stated that his specimens from Madras “agreed completely with Haswell’s description and figure”. One of us (CLM) has also seen these specimens (BMNH 1892: 7: 15: 152–155) from Madras and three of them are the same as the lectotype of C. artificiosus , but one is not. This specimen is a Conchoecetes intermedius Lewinsohn, 1984 male (16.4 x 15.9 mm, now designated BMNH 1892 7. 15. 155). Conchoecetes conchifera is certainly more similar to C. intermedius than it is to C. artificiosus . Henderson obviously formed the conclusion that C. artificiosus was a variable species leading him to incorrectly decide that Haswell’s species was synonymous.

Characters which separate C. conchifera ( Fig 12 ) from C. artificiosus ( Fig 2 ) include simple evenly convex anterolateral margin with fine granules, but no notches (versus complex, sculptured, dentate in C. artificiosus ); carapace regions weakly defined (regions well defined by deep grooves); and behind cervical and posterolateral grooves are blunt swellings rather than distinct teeth (strong distinct teeth following each groove). Both of the above species have a distinct anterolateral margin so that in dorsal view the subhepatic area is not visible dorsally whereas in C. intermedius the carapace surface continues evenly on to the subhepatic area without interruption so that the subhepatic area is visible dorsally. This surface is evenly granulated. Conchoecetes intermedius has no anterolateral teeth and carapace regions are not defined by grooves. It grows to a much larger size than the other two species ( Table 1 ).

Use of bivalve shells for camouflage by C. conchifera in Moreton Bay , Australia, has been reported by McLay & Hosie (2012) (as Conchoecetes artificiosus s.l.). In the same paper shell-use by other dromiids is compared. The three genera Hypoconcha , Desmodromia and Conchoecetes each employ different morphological adaptations for shell-acquisition, but they all share a life style which involves living in a closet world of twilight beneath a shelter where visual signals are little –used and chemical signals predominate.

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 11. Conchoecetes conchifera (Haswell, 1882). A, AM-P3895, paralectotype, female 15.9 × 16.7 mm, dorsal view; B, AM-P3895, lectotype, female, 19.9 × 20.8 mm, dorsal view of anterior half with some setae removed to expose anterolateral margin and chelae (photographs by Shane Ahyong).

FIGURE 12. Conchoecetes conchifera (Haswell, 1882), WAM58-83, male, 23.6 × 23.7 mm, Shark Bay, Western Australia. A, dorsal view; B, frontal view; C, ventral view of oral and orbital area.

FIGURE 13. Conchoecetes conchifera (Haswell, 1882), WAM58-83, male, 23.6 × 23.7 mm, Shark Bay, Western Australia. A, outer face of right chela; B, dorsal face of right chela; C, ventral view of pleon; D, dorsal view of right P4.