Gordonopsis pacifica Takeda & Suyama, 2019

Ng, Peter K. L. & Forges, Bertrand Richer de, 2020, A revision of the deep-sea porter crabs of the genus Gordonopsis Guinot & Richer de Forges, 1995 (Crustacea, Decapoda, Brachyura, Homolidae), with descriptions of five new species, Raffles Bulletin of Zoology 68, pp. 267-307 : 285

Gordonopsis pacifica Takeda & Suyama, 2019

( Figs. 14–16 )

Gordonopis pacifica Takeda & Suyama, 2019: 46 , figs. 1B, 2–4.

Material examined. Holotype: male (31.0 × 43.0 mm) (NSMT-Cr 26053), south of Okinotorishima (= Okinotori Island), 20°25′31″N, 136°04′52″E, southern Japan, 300–600 m deep, coll. 13 January 2006.

Diagnosis. Male: carapace longitudinally ovate, width to length ratio 0.72, distinctly wider posteriorly than anteriorly; dorsal carapace surface with well-defined regions, separated by broad, deep grooves; lateral margin gently convex; dorsal parts with numerous setae that partially obscure surface; lateral parts with soft setae that almost obscure surface, denser on hepatic, pterygostomial and suborbital regions ( Figs. 14 A–C, 15A, B). Rostrum long, sharp, with 2 relatively short, obliquely directed pseudorostral spines, just shorter than rostrum ( Fig. 14B ). Supraorbital margin relatively wide; pseudorostral spines directed obliquely laterally at angle of about 20° ( Fig. 14B ). Eyes with short ocular peduncle, cornea prominent; no discernible orbit ( Fig. 14B ). Hepatic region gently inflated, with short obliquely directed spine ( Fig. 14B ). Gastric region without spines ( Fig. 14B ). Gastric groove well marked, with distinct ovate gastric fossae just above ( Fig. 14B ). Cardiac region swollen; branchial region inflated, with distinct branchio-cardiac grooves ( Fig. 14B ). Latero-posterior tubercle on carapace not distinct, just discernible as low tubercle ( Fig. 14B ). Base of antenna with short spine. Antennal flagellum short, second and third articles thick, setose. Epistome triangular. Third maxilliped pediform, merus elongate with dentiform external angle ( Fig. 15C ). Chelipeds long; fingers long, greater than half length of palm; surface almost smooth with low slightly oblique longitudinal ridge; carpus longitudinally ovate, outer margin with 3 long spines, distal edge with 1 long spine, inner margin with 1 long spine, dorsal surface with longitudinal row of 3 short spines; merus triangular in cross-section, relatively long, curved, dorsal margin with 7 or 8 spines and distal 2 short spines bracketing chela, outer ventral margin with 7 or 8 spines, inner ventral margin with 6 short spines ( Figs. 14A , 15 E–G). Ambulatory legs long; basis-ischium with 4 spines on each margin; P2 merus with 3 or 4 spines on dorsal margin (excluding 1 distal spine), ventral margin with 1 or 2 spines; P3 merus with 2 spines on dorsal margin (excluding 1 distal spine), ventral margin with 1 spine; P4 merus with 2 spines on dorsal margin (excluding 1 distal spine), ventral margin with 1 spine, outer surface with 1 proximal tubercle ( Figs. 14A , 16 E–G, I, K, L). P5 merus slender, unarmed on all margins, reaching just beyond gastric groove when folded anteriorly; carpus long, propodus short, enlarged, forming prominent pseudochela with stout, gently curved dactylus; occlusal margin of fixed finger with 7 spines, that of dactylus with 8 spines ( Fig. 16A, H, J ). Outer margin of P2 coxa with l short, stout spine on distal edge; outer margin of P3 coxa with 1 short, stout spine on proximal edge, outer margin of P4 coxa with 1 or 2 short, stout spines on proximal edge ( Fig. 16C, D ). Pleon missing from holotype.

Colour. The freshly collected specimen has a yellowishbrown carapace with the chelipeds and ambulatory leg bright red ( Takeda & Suyama, 2019: fig. 1B).

Remarks. The holotype specimen is in poor condition with several parts of the carapace damaged, pereiopod missing and most of the pleon absent. It appears to have recently moulted given that the cuticle is not completely hardened and still quite brittle. Some of the spines on the pereiopods are broken off but their bases can still be discerned.

See general discussion for comparisons with congeners.

Figures

Fig. 14. Gordonopsis pacifica Takeda & Suyama, 2019, holotype male (31.0 × 43.0 mm) (NSMT-Cr 26053), Okino-Torishima Island, Japan. A, overall habitus; B, dorsal view of carapace; C, dorso-frontal view of carapace.

Fig. 15. Gordonopsis pacifica Takeda & Suyama, 2019, holotype male (31.0 × 43.0 mm) (NSMT-Cr 26053), Okino-Torishima Island, Japan. A, lateral view of cephalothorax; B, frontal view of cephalothorax; C, left third maxilliped; D, dorsal view of front; E, outer view of merus and carpus of right cheloped; F, outer view of right chela; G, dorsal view of carpus of right cheliped.

Fig. 16. Gordonopsis pacifica Takeda & Suyama, 2019, holotype male (31.0 × 43.0 mm) (NSMT-Cr 26053), Okino-Torishima Island, Japan. A, dorsal view of carapace showing relative P5 length; B, sternopleonal cavity; C, right P2–P4 coxae and basis-ischia; D, left P2–P4 coxae; E–H, left P2–P5, respectively; I, dorsomesial view of proximal part of merus of P4 showing tubercle on outer surface (arrow); J, left P5 pseudochela; K, L, right P2 and P3, respectively; M, N, left G1; O, left G2. All ambulatory legs shown to same scale. M–O after Takeda & Suyama (2019: fig. 4B–D).