Conchoecetes investigator, Naruse, 2019

Naruse, Tohru, 2019, Revision of the shell-carrying crab genus Conchoecetes Stimpson, 1858 (Crustacea: Brachyura: Dromiidae), Zootaxa 4706 (1), pp. 1-47 : 31-34

Conchoecetes investigator n. sp.

( Figs. 17 , 18 )

Conchoecetes artificiosus — Alcock 1899: 151 (in part); 1901: 42 (in part, specimen 1206/7 from Port Blair) [not Conchoecetes artificiosus ( Fabricius, 1798) ]

Type: AM P2622 , ovig. female 18.1 × 18.2 mm, “Investigator” reg. no. 1206, Port Blair , Andaman Is., Bay of Bengal, 11º 67’N, 92º 73’E, coll. G. H. Booley.

Description. Surface of carapace smooth, cervical, posterolateral and cardiac grooves well marked. Rostrum distinctly tridentate, lateral teeth broad, median tooth sub-acute and on lower level, but visible dorsally. Supraorbital tooth distinct, no post-orbital tooth, suborbital margin with distinct suborbital tooth and group of rounded granules. Anterolateral margin sinuous slightly concave after postorbital corner, followed by convex section adorned by group of 3 or 4 small rounded granules and then short concave section anterior to distinct blunt anterolateral tooth behind cervical groove at widest part of carapace. Anterior to this tooth is small subhepatic granule on lower level. Posteriorly margin continuous to small posterolateral tooth behind posterolateral groove. Carapace margin converges to corner and concave posterior margin. Ventrally subhepatic area has oblique row of small granules curving towards corner of buccal frame.

Female 7/8 sutures convergent ending apart in short tubes between bases of P2.

Third maxillipeds operculate, crista dentata with 7 to 8 small teeth on inner margins.

Chela carpus ventro-distal border with large blunt tubercle surrounded by ~10 smaller granules; propodus dorsal border and outer face with ~10 small scattered granules and 2 large distal tubercles on dorsal surface at base of dactyl. Inner margins of both fingers setose, armed with 6 or 7 interlocking white teeth. P2 and P3 carpus dorsal margin has row of 3 prominent tubercles ending at prominent distal “knob”/tubercle. Anterior margin pf P4 carpus armed with 4 or 5 conspicuous sub-acute tubercles that resemble teeth. Anterior margin of propodus also has several large granules. Dactylus relatively short, stout, curved talon-like longer than propodus which bears prominent quadrangular projection forming shell-carrying mechanism with dactylus.

Female telson triangular, posterior margin curved, uropods visible externally.

Etymology. The specific name is an allusion to the fact that the type specimen was collected by the Royal Indian Marine Survey Ship “Investigator”. It is a noun used in apposition.

Distribution. Known only from the type locality, Port Blair, Andaman Islands, depth unknown.

Remarks. The specimen of this new species was discovered in the collection of the Australian Museum. It was donated to the AM on the assumption that it was an example of Conchoecetes artificiosus . The label indicates that the specimen, registration number 1206/7, was collected by the Royal Indian Marine Survey Ship “Investigator” from Port Blair, Andaman Islands. Date of the collection is not given, but could have been in 1888, 1890 or 1898 years when the “Investigator” visited the Andaman Islands ( Alcock 1902). There is no additional information about the depth or habitat where the specimen was taken (see A Naturalist in Indian Seas; or, Four Years with the Royal Indian Marine Survey Ship ‘Investigator’. London: John Murray, 1902). The station list given by Alcock (1901, p42) refers to “ 1206-1207 /7” indicating that there was another specimen collected at the same time. This material is probably a part of the ZSI collection, Calcutta, The distinctive characters differentiating Conchoecetes investigator from C. artificiosus include flattened broad lateral rostral teeth with denticulate margins (triangular non-denticulate sub-acute teeth in C. artificiosus ); anterolateral margin is sinuous, markedly concave beyond postorbital corner, without interruption while subhepatic area has several granules visible dorsally (margin convex, diagonal row of subhepatic granules); blunt tooth behind cervical groove marking widest point and well developed posterolateral tooth behind branchial groove (both teeth prominent); prominent comb of 4–5 short stout tubercles on the anterior margin of the carpus of P4 (tubercle row absent); distal corner of carpus and propodus of P2 and P3 have prominent blunt knobs (absent).

Conchoecetes investigator differs from C. andamanicus in having a tridentate rostrum with shorter medial tooth but still visible dorsally (whereas C. andamanicus has short triangular lateral teeth but median tooth very small deflexed not visible dorsally); small but distinct supraorbital tooth (no supraorbital tooth); clearly defined carapace regions (weakly defined regions); sculptured anterolateral margin (linear denticulate margins); anterolateral and posterolateral teeth evident (neither teeth evident); four prominent tubercles forming a comb-like structure on anterior margin of the merus of P4 (margin evenly granulated).

Figures

FIGURE 17. Conchoecetes investigator n. sp., AM-P2622, holotype, ovigerous female, 18.1 × 18.2 mm, Andaman Is., Indian Ocean. A, dorsal view; B, frontal view; C, ventral view of oral and orbital area.

FIGURE 18. Conchoecetes investigator n. sp., AM-P2622, holotype, ovigerous female, 18.1 × 18.2 mm), Andaman Is., Indian Ocean, A, outer face of right chela; B, dorsal view of right chela; C, ventral view of telson and pleon; D, carpus of right P4.