Conchoecetes intermedius Lewinsohn, 1984,

Naruse, Tohru, 2019, Revision of the shell-carrying crab genus Conchoecetes Stimpson, 1858 (Crustacea: Brachyura: Dromiidae), Zootaxa 4706 (1), pp. 1-47: 26-31

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Conchoecetes intermedius Lewinsohn, 1984


Conchoecetes intermedius Lewinsohn, 1984 

( Figs. 14–16View FIGURE 14View FIGURE 15View FIGURE 16)

Conchoecetes intermedius Lewinsohn 1984: 119  , fig. 4 a–g (type);— Guinot & Tavares 2000: 307, fig. 4 e–g; 2003, 54, fig. 3B–C;—Ng et al 2000: 157, fig. 1c;— Ng et al 2001: 5;—Cleva et al 2007: 239, fig. 7A;— Ahyong et al 2009: 33, figs 9, 10.;— Shen & Jeng 2005: 18.;— Ng et al. 2017: 25;—Ng et al 2008: 33.

Conchoecetes artificiosus — Henderson, 1893: 407  (part); Rathbun 1910: 367 (part from Koh Chuen). [Not Conchoecetes artificiosus  ( Fabricius, 1798].

Conchoecetes canaliculatus Yang & Dai 1994: 127  , 145, fig. 3 a–f.

Conchoecetes andamanicus —Serène & Lohavanijaya 1973: 12  , figs. 1–4; pl. I, A–D. [Not Conchoecetes andamanicus Alcock, 1900  ]

Conchoecetes mutus — Sakai 1999: 14  , pl. 4F. [Not Cancer mutus Linnaeus, 1758: 625  , = Tetralia muta ( Linnaeus, 1758)  see Castro et al, 2004].

Conchoecetes  sp.—Chang 1963: 6, pl. 1, fig. 2.

Type. MNHN-B6891, holotype, male, 17.0 × 16.0 mm, Nosy Komba , Madagascar, 13º8’S, 48º21’E, 10 m (not examined)GoogleMaps  .

Material examined. India: BMNH 1892: 7: 15: 155, male 16.4 × 15.9 mm, Madras, coll. J.R. Henderson, originally identified as C. artificiosus    ; ZRC2001.0899View Materials, male 31.0 × 31.0 mm, Tranquebar, Tamil Nadu, South India , coll. N.K. Ng & A.S. Fernando, 16 & 24 Mar. 2001  .

Sri Lanka: BMNH 1907:5:22:3, male, 6.7 × 7.0 mm, Trincomalee, coll. W.A. Herdman  ; BMNH 1934: 1: 16: 7, 2 females 7.7 × 6.7 mm, 6.8 × 6.3 mm (damaged), coll. W.A. Herdman. 

Andaman Islands: USNM 1277741, immature female about 5 × 5 mm, 93ºE, 10ºN, South of Andaman Is. (photograph examined).

Myanmar: BMNH 1984: 524, immature female 13.7 × 13.5 mm, Gulf of Martaban,

Thailand: USNM39828View Materials, soft damaged, ~13 × 12 mm, Gulf of Siam, Koh Chuen , 55m, shell bottom (photograph examined), coll. Th. Mortensen  ; ZRC1999.0079View Materials, female 25.9 × 25.5 mm, Thailand, Ko Ma , off Ko Phi Phi, 25m, 19 Nov. 1986  ; ZRC2003.0123View Materials, male 28.9 × 29.0 mm, Pattani Province, Nong Chik District, Bong Tawa crab fishing village, coll. D.C.J. Yeo et al., 20 Feb. 2003  ; ZRC2003.0189View Materials, 2 males 32.2 × 32.0, 32.5 × 31.4 mm, Pattani Province, Saben Crab Landing, Z. Jaafar et al., 8 Jun. 2003  ; ZRC2000.0874View Materials, female 28.0 × 27.5 mm, Pishai Fish Port, Phuket Fish Port , coll. C. Schubart et al., 2000  ; ZRC 2017.0459View Materials, male 39.2 × 35.4 mm, Sattahip , Chonburi Province, coll. Nongnud Leelapiyanart, 2011  .

China: USNM62030View Materials, female 42 × 38mm, Amoy, Xiamen Is., 118º04.55’E, 24º28.47’N, donated by S.F. Light (photograph examined)GoogleMaps  .

Singapore: BMNH 1905: 10: 21: 5, female 19.4 × 18.7 mm, Pasa Panjang , 3.6–5.5 m, just outside seaweed zone, coll. F.P. Bedford & W.F. Lanchester  ; ZRC1993.0321View Materials ovig. female 21.8 × 21.5 mm, South China Sea , near Singapore, coll. Hee Hart, 15 Dec. 1982  .

Papua New Guinea: MNHN CP4457View Materials, male 13.5 mm × 14.8 mm, KAVIENG 2014, 2° 33' 24.5988'' S; 150° 41' 20.382'' E, 133–178 m, Feb. 2014GoogleMaps  .

Vietnam: Ondrej Radosta Collection, male 33.0 × 32.0 mm (photo examined), Phan Thiet Mui Ne Beach, South Central Coast.

Australia: QM-W16124, female 6.2 × 7.0 mm, Northwest Shelf , CSIRO “Soela”, 19º29.0’S, 118º53.5’E, 40 m, 12 Feb. 1983GoogleMaps  ; QM-W16160,?sex 3.4 × 4.0 mm, Northwest Shelf , CSIRO “Soela”, 19º59.1’S, 117º49.0’E, 43 mGoogleMaps  ; QM-W16163, soft male 4.9 × 5.0 mm, Northwest Shelf , CSIRO “Soela”, 19º57.5’S, 117º50.0’E, 42 m, 25 Jun. 1983GoogleMaps  ; QM-W16172, female 6.6 × 6.5 mm Northwest Shelf, CSIRO “ Soela ”, 19º05.0’S, 118º54.2’E, 82 m ,, 29 Jun. 1983GoogleMaps  ; QM-W16174, male 9.4 × 9.7 mm, Northwest Shelf , 19º04.6’S, 118º57.9’E, CSIRO Soela, 81–82 m, 30 Jun. 1983GoogleMaps  ; QM-W16189, male 11.6 × 11.4 mm, parasitized by rhizocephalan, Northwest Shelf , 84 m, 7 Dec. 1982  ; WAM C40671View Materials, male 19.2 × 19.3 mm, Ningaloo Marine Park , Off Osprey Sanctuary, 58– 57m, 22°15’41’S, 113°4804’–22°1445’S, 113°48’29”E, 23 Apr. 2006  ; WAMC15514, male 29.7 × 29.2 mm, 102 km NW of Port Hedland , approx. 19ºS, 118ºE, 5 Oct  , 1998.

Description. Carapace as wide as long, sub-pentagonal, dorsal surface smooth, evenly convex, covered by short sparse soft tomentum; immature specimens not marked by any grooves except a faint branchial groove behind which is a laterally directed ridge as it nears the lateral margin (as shown by Lewinsohn, 1984 fig 4a; However, in specimens larger than the type (17 × 16 mm) the cardiac, branchial and cervical grooves become evident). Rostrum tridentate, lateral teeth short, distally rounded, median tooth shorter than laterals and deflexed, scarcely visible dorsally. Supraorbital tooth present, no post-orbital tooth, suborbital tooth blunt. Anterolateral margin obtuse, triangular area covered in rounded granules extends posteriorly towards the widest point; in larger specimens there can be a row of irregular granulated tubercles at level of post-orbital corner, not forming a distinct edge but with surface grading ventrally into granular sub-hepatic area; widest point is a rounded shoulder between lateral ends of cervical lacking a tooth; posterolateral margins convergent, not interrupted by posterolateral tooth. Posterior carapace margin concave.

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

Third maxillipeds operculiform, evenly granular, crista dentata 13–14 stout teeth on inner margin.

Chela carpus granular, with two low and not prominent protuberances on distal outer margin of dorsal surface; propodus also strongly granular on outer face, dorsal surface with ~ 10 larger granules along inner dorsal edge; inner propodal face setose, fingers hollowed out internally, down-curved armed with several interlocking teeth. P2 dactylus with 3 rows of short setae, P3 dactylus with 2 rows, inner margins of both have ~20 tiny adpressed spines. P4 carpus anterior margin has 4–5 small granules, talon short, stout, fringed with setae, just over-reaching large propodal projection, but not exceeding carpus-propodal joint.

Male telson triangular, uropods well developed, visible externally, holding pleon in place by locking in front of tubercles on coxae of P2, aided by concave margins of fourth segment fitting against small tubercles on coxae of P3. Female telson much wider than long, posterior margin convex, all segments fringed with long setae with strong central ridge.

Colour. A photograph of the male from PNG shows a pale cream ground colour with patches of orange on the carapace and pleon; pereopods partially yellow, dactyli orange; cheliped teeth bright pink ( Fig. 16AView FIGURE 16). A dried male from Vietnam has the carapace, cheliped teeth and P5 bright pink ( Fig. 16BView FIGURE 16).

Habitat. Sandy mud, and shells. Depth range 2– 84 m.

Distribution. Madagascar (type locality), Sri Lanka, India, Myanmar, Thailand, Vietnam, China, Taiwan, Singapore, Northwest Australia. New Guinea. We examined a photo taken by Ondrej Radosta of a male, 38.0 × 40.0 mm, from Penghu, Taiwan. Conchoecetes intermedius  is a widespread Indo-West Pacific species.

Remarks. The specific epithet “ intermedius  ” was chosen by Lewinsohn (1984) to indicate that his new species was “intermediate” between C. artificiosus  ( Fig. 2View FIGURE 2) and C. andamanicus  ( Fig. 3View FIGURE 3). Conchoecetes artificiosus  has a flattened, deeply-grooved carapace surface; pronounced structured anterolateral margin with hepatic notch and teeth, overhanging a sub-hepatic area adorned with an oblique row of blunt granules. By comparison in C. andamanicus  carapace regions are not well defined, although the cervical and branchial grooves are evident; anterolateral margin forms a distinct evenly granulated, unstructured edge overhanging the sub-hepatic area adorned with 4 or 5 blunt granules not arranged in a row. Conchoecetes intermedius  lies between these two species in having a smooth carapace, with regions not well-defined by grooves; lacking a distinct anterolateral edge, making the dorsal surface and hepatic area continuous uninterrupted by teeth or notches. The discovery of this species by Lewinsohn (1984) was important because it gave polarity to the characters defining the anterolateral margin with C. intermedius  representing the “minimalist” condition in terms of structure by having an obtuse margin not adorned with tubercles. In other species in this genus the margin can be more distinctly edge-like and tuberculate. By this view the specific name that he chose was not totally appropriate: C. andamanicus  at least has a distinct edge, admittedly unstructured, whereas C. intermedius  has none while, at the opposite pole, C. artificiosus  has a highly structured arrangement. This contrasting of the anterolateral margin characters is a major element of the present revision.

Somewhat presciently, Rathbun (1910) noted that “the male [Koh Chuen, 30 fath., shell bottom; II; 1M] seems half-grown and intermediate between C. andamanicus  and typical C. artificiosus  : the front is cut into two triangular teeth, with the inferior denticle slightly visible in dorsal view; there is a rudimentary tooth on the upper border of the orbit; no traces of lateral teeth, the sides being arcuate; subhepatic region not bounded by distinct rows of tubercles or granules.” This is almost certainly C. intermedius Lewinsohn, 1984  .

Conchoecetes canaliculatus Yang & Dai, 1994  , was reported from the Spratly Islands (also known as the Nansha Islands), South China Sea, and approximately 10ºN by 114ºE. The text and their figures are not entirely in agreement, but the comparison of their specimen with Lewinsohn’s type highlights the presence of weak cervical and branchial grooves, to which their specific name alludes. This is the result of comparing their adult specimen (31 × 33 mm female) with the type which is an immature male (17 × 16 mm). Comparison of our present material shows that these grooves become more evident as size increases. Their species is synonymous with C. intermedius Lewinsohn, 1984  (Ng et al. 2000). When identifying specimens of this species it is important that comparisons are made between crabs of similar size.

Conchoecetes intermedius  was reported from Thailand by Serène & Lohavanijaya (1973) as Conchoecetes andamanicus  , but their figs. 1–4; pl. 1 figs. A–D clearly show that the specimen is C. intermedius  . This report predated Lewinsohn (1984) so at that time C. andamanicus  was the most similar species. However, C. andamanicus  differs from C. intermedius  in several ways: it has a distinct anterolateral margin which is evenly lined with small granules and the cervical and branchial grooves are distinctly marked.

Sakai (1999) examined Herbst’s dried collection in the Berlin Zoological Museum (see Gruner 1970) and provided a photograph of a specimen which he referred to as Conchoecetes mutus Linnaeus, 1758  , but it is clearly Conchoecetes intermedius Lewinsohn, 1984  . Herbst (1803) does use Linnaeus’ name, without an illustration, but the descriptions by both authors make no mention of the key feature, talon-like P4’s. There can be little doubt that Linnaeus was not referring to a species of Conchoecetes  and that Conchoecetes mutus  is not a prior name for Lewinsohn’s species. Castro et al. (2004) argue that Cancer mutus Linnaeus, 1758  , is most likely Tetralia muta ( Linnaeus, 1758)  in the family Tetraliidae Castro, Ng & Ahyong, 2004  .


Smithsonian Institution, National Museum of Natural History


Museum National d'Histoire Naturelle


Australian National Fish Collection


Western Australian Museum














Conchoecetes intermedius Lewinsohn, 1984

Naruse, Tohru 2019

Conchoecetes intermedius

Ng, P. K. & Shih, H. - T. & Ho, P. - H. & Wang, C. - H. 2017: 25
Ahyong, S. T. & Naruse, T. & Tan, S. H. & Ng, P. K. L. 2009: 33
Shen, Y. L. & Jeng, M. S. 2005: 18
Ng, P. K. L. & Wang, C. - H. & Ho, P. - H. & Shih, H. - T. 2001: 5
Guinot, D. & Tavares, M. S. 2000: 307
Lewinsohn, C. 1984: 119

Conchoecetes artificiosus — Henderson, 1893: 407

Rathbun, M. J. 1910: 367
Henderson, J. R. 1893: 407

Conchoecetes canaliculatus

Yang, A. & Dai, S. - L. 1994: 127

Conchoecetes mutus —

Sakai, K. 1999: 14
Linnaeus, C. 1758: 625