Conchoecetes andamanicus Alcock, 1900

Naruse, Tohru, 2019, Revision of the shell-carrying crab genus Conchoecetes Stimpson, 1858 (Crustacea: Brachyura: Dromiidae), Zootaxa 4706 (1), pp. 1-47 : 8-10

Conchoecetes andamanicus Alcock, 1900

( Fig. 3 )

Conchoecetes andamanicus Alcock, 1900: 152 ; 1901: 43, pl. III, fig. 17;— Laurie 1906: 353;— Ihle 1913: 50;— Davie & Ng 2002: 314 (list);— Ng & Davie 2002: 370 (list);—Ng et al 2008: 33 (list);— Trivedi et al 2018: 35 (list).

Conchoecetes andamanicus —Serène & Lohavanijaya 1973: 12 , figs 1–4, pl. 1 A–D. [= Conchoecetes intermedius Lewinsohn 1984 . Not Conchoecetes andamanicus Alcock, 1900 ].

Type. Andaman Islands: ZSI-2859/7, lectotype (herein designated), male, 8.0 × 9.2 mm, and 2 paralectotypes (herein designated)— 1 male, 7.0 × 8.6 mm, 1 damaged female, 5.8 × 5.6 mm, Port Blair, coll. G.H. Booley. We have examined photographs of this material.

When Alcock (1900) described Conchoecetes andamanicus , he said that he had “three small specimens”. None of them were designated as the holotype, so all three specimens are the syntypes (see ICZN 1999: Art. 72.1.1). Later Alcock (1901) gave more details about one of these specimens, the largest male “7.0 × 7.5 mm,” from the Andaman Islands, registered in the Indian Museum ( ZSI) as “2859/7 Port Blair, coll. G.H. Booley”. Examination of these specimens by Santanu Mitra, resulted in the following data: largest male, 8.0 × 9.2 mm, smaller male, 7.0 × 8.6 mm, and a damaged female, 5.8 × 5.6 mm, and there is no label in the container indicating they are types. Although the present measurements do not agree exactly with Alcock we have no doubt that they all refer to the same material. When size estimates involve pliable material with or without marginal structures included there will always be imprecision. We designate the largest male 8.0 × 9.2 mm as the lectotype and the two others become paralectotypes. The photograph provided herein is of the male paralectotype ( Fig. 3B ).

Material examined. Andaman Is.: USNM 1277741, photographs of a small immature female about 5.0 × 5.0 mm, coll. south of Andaman Is., 10ºN, 93ºE.

Australia: AS0283-133 , mature female, 4.8 × 4.9 mm, Western Australia, Broome , 19º4.4’S, 118º43.3’E,

82 m, coll. A.J. Bruce, 28 Apr. 1983; WAM C26226, male, 5.9 × 5.8 mm with eroded bivalve shell, Dampier Archipelago, Lady Nora I., 20°21.79’S, 116°38.05’E to 20°22.00’S, 116°37.81’E, 38.5 m, sand and rock, hydroids, coll. S. Slack-Smith & M. Hewitt, 17 Jul. 1999 ; QM-W16146, immature female, 4.3 × 3.9 mm, Northwest Shelf , Port Hedland , 19º30.9’S, 118º48.7’E, 40– 39 m , CSIRO “Soela”, 26-04-1983; QM-W16192, male 5.1 × 4.9 mm

with bivalve shell, 19º45.8’S, 117º52.1’E, 52 m, CSIRO “Soela”, 2 Sep. 1983 .

Sri Lanka: BMNH 1934:1:16:5, soft male 10.3 × 10.0 mm, Pearl Banks, Gulf of Mannar, coll. WA Herdman presented by Miss Herdman.

Description. Carapace truncated sub-pentagonal shape; surface almost flat, finely granulate, soft tomentum, with setose fringe; regions not well-defined, only mesogastric groove evident in mid-line, some cardiac grooves evident, cervical and branchial grooves strongest near margins. Rostrum short, lateral teeth blunt, divergent, downcurved, median tooth much shorter than lateral teeth, scarcely evident dorsally; slight concavity in supra-orbital margin directly above eyes, no distinct supraorbital tooth, suborbital margin convex, separated by fissure, not visible dorsally. Sub-hepatic area with 4 or 5 larger blunt granules, not visible dorsally; remaining area finely granulate, no distinct rows of granules. Anterolateral margin entire, distinctly edged, overhanging hepatic area, without hepatic notch, and teeth; edge mostly minutely granulate with a few larger granules, slightly convex to widest point behind cervical groove. Margin behind groove curved, not dentiform. Branchial groove at carapace margin not marked by tooth only small granule.

Third maxillipeds operculate, crista dentata with 5 small sharp teeth.

Chela densely covered with tiny granules; carpus with 2 large distal blunt tubercles; propodus outer surface minutely granular, but granules on inner margin not arranged in a row as shown by Alcock (1901, pl3, fig 17). Single prominent blunt propodal tubercle at base of fingers. P2 & P3 articles covered in minute granules, dactyli dorsal margins with row of setae, inner margin armed with 10 or 11 very small adpressed spines. P4 minutely granulated, anterior margin of carpus with some larger granules, one prominent tubercle but none arranged in a row-like manner; talon (dactylus) comparatively large, long, curved, acute, reaches back to merus-carpal joint, thus no direct engagement with the propodal extension. P5 sub-dorsal flattened, dactylus short hooked at right angle (twisted).

Male telson broadly triangular, posterior margin convex, uropods visible externally locking in front of small tubercles on P2 coxae.

Habitat. Sand and rock; with hydroids. Depth range 38– 82 m. Ihle (1913) collected two females from 32 m, west of New Guinea.

Distribution. Sri Lanka ( Ceylon), Andaman Islands (type locality), Western Australia, Western New Guinea.

Remarks. Alcock (1900) was unsure of the status of three small specimens amongst the collection from the Andaman Islands, so cautiously named them Conchoecetes andamanicus (followed by a question mark), but this species is valid and differs from C. artificiosus in having no supraorbital tooth, Fig. 3 (present in C. artificiosus , Fig. 2 ); carapace regions weakly marked (deeply marked); anterolateral margins not sculptured (complex with notches); anterolateral and posterolateral teeth only weakly developed (both teeth strongly developed); single large tubercle at base of cheliped fingers (two unequal tubercles). Lewinsohn (1984: 122, 123) presented a detailed comparison of C. intermedius with C. andamanicus and C. artificiosus .

Conchoecetes andamanicus seems to be one of the smallest species in the genus: the male type specimen is only ~ 8 mm CW ( Table 1 ). Males examined here, CW 5–6 mm, appear to have well developed mature gonopods and the female has a mature sized pleon suggesting that this species matures at a very small size, around 5 mm CW. Laurie (1906) reported a male CW = 10.25 mm from the Pearl Banks (the same specimen was examined herein), which seems to be the largest known. We can compare these specimens with the megalopae of Conchoeodromia alcocki (which may be a synonym of C. artificiosus , see Guinot & Tavares, 2000) reported by Chopra (1934) viz. 6.2 × 5.2 mm and 5.6 × 4.1 mm) which are bigger than the ovigerous C. andamanicus crab collected by Ihle (1913). Where known most of the other Conchoecetes species mature at around three times larger. The exception is Conchoecetes pectenicola whose type is a small ovigerous female 6.2 × 6.2 mm, but it grows to more than 20 mm CW.

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 3. Conchoecetes andamanicus Alcock, 1900, ZSI-2859/7, paralectotype, male, 7.0 × 8.6 mm, Port Blair, Andaman Is. (photographs by Santanu Mitra). A, dorsal view; B, ventral view.