Trogloplax Guinot, 1986

Ng, Peter K. L. & Castro, Peter, 2016, Revision of the family Chasmocarcinidae Serène, 1964 (Crustacea, Brachyura, Goneplacoidea), Zootaxa 4209 (1), pp. 1-182 : 131-134

Genus Trogloplax Guinot, 1986

Trogloplax Guinot, 1986: 308 ; 1988: 27.— Jamieson & Guinot 1996: 289.—Ng et al. 2008: 76 [in list].— De Grave et al. 2009: 33 [in list].—Castro et al. 2010: 41 (part).— Guinot et al. 2013: 42, 113.

Type species. Trogloplax joliveti Guinot, 1986 (by monotypy, gender feminine)

Diagnosis. Carapace ( Fig. 93 E–H; Guinot 1986: pl. 1, fig. A, B; pl. 2, fig. A; 1988: pl. 4, fig. 1, 5, fig. 17A) transversely oval, front bilobed, with shallow median cleft; anterolateral margins arcuate, with shallow, undulating crest lacking defined teeth. Epistome ( Fig. 94 E, F; Guinot 1986: pl. 2, fig. B; 1988: fig. 16A) narrow, posterior margin with short, semicircular median lobe with median fissure, semicircular lateral margins. Eye peduncle ( Fig. 94 E, F; Guinot 1988: fig. 16) reduced, not filling orbit, mobile; cornea reduced, non-pigmented. Third maxillipeds ( Fig. 94 J; Guinot 1986: pl. 2, fig. B; 1988: fig. 17B) leaving gap when closed; merus quadrate, anteroexternal angle rounded; ischium quadrate, about same length as merus. Chelipeds ( Figs. 93 E, H; 95G, H; Guinot 1986: pl. 1, fig. C–E; 1987: pl. 2, fig. H, I; 1988: pl. 4, fig. 2–4, 6–8) subequal in length, slightly dissimilar in both sexes; cutting margins of major chelae with small teeth in both sexes; fingers of minor chela ( Fig. 95 H) subcircular in crosssection, not laterally flattened, gently tapering to tip, shear-like, cutting margins with few low teeth; anterior margin of dorsal surface of propodi with large tooth; inner margin of cheliped carpus ( Fig. 95 G, H; Guinot 1987: pl. 2, fig. H, I) with conspicuously long tooth, inner margins of meri ( Fig. 95 G, H; Guinot 1987: pl. 2, fig. H, I) with 1, 2 pointed teeth, outer margins with 3 tubercles in male holotype. Proportionally long ambulatory legs ( Fig. 93 E, G, H), P5 merus reaching front when folded. Meri of ambulatory legs unarmed. Fused thoracic sternites 1, 2 ( Fig. 97 A, B, D; Guinot 1986: pl. 2, fig. C; 1988: fig. 17C; Guinot et al. 2013: fig. 24A) broadly triangular, long; fused sternites 3, 4 relatively broad. Male pleon ( Fig. 97 A–C; Guinot 1988: fig. 17F) with lateral margins of somite 6, fused somites 3‒5 nearly straight; postero-lateral regions only slightly swollen; telson proportionally short. Sternopleonal cavity of male deep. Press-button for pleonal holding as small, short tubercle posterior to thoracic sternal suture 4/5 near edge of sterno-pleonal cavity ( Fig. 98 D). Male thoracic sternite 8 ( Figs. 97 C, E; Guinot 1986: pl. 2, fig. D; 1988: fig. 17D) proportionally long, rectangular; “supplementary plate” conspicuously narrow, only reaching median portion of exposed thorax, short, slightly longer at rounded outer margin. G1 ( Fig. 98 E, G, H; Guinot 1986: pl. 2, fig. E, F, F1; 1988: fig. 17E; Guinot et al. 2013: fig. 24B) stout, distal part with tapering tip, covered with short spinules. G2 ( Fig. 98 F, J; Guinot 1986: pl. 2, fig. G) as long as or longer than G1, basal segment curved; distal segment slightly longer than basal segment, apex with lateral pointed tip. Somites of female pleon ( Fig. 99 G) with slightly convex lateral margins; telson proportionally long. Sterno-pleonal cavity of female ( Fig. 99 H) moderately deep, with conspicuously large vulvae widely separated, covering full extent of thoracic sternite 5, round, thin, raised lip on outer margin, soft membrane across, leaving proportionally small opening.

Remarks. The G2 of T. joliveti is as long as ( Fig. 98 E, F) or longer than the G1 ( Fig. 98 G, J), and similar to the two species of Australocarcinus (the second trogloplacine genus) where males are known, where the G2 is distinctly longer than the G1 ( Fig. 98 A–D) (see below). Guinot (1996: 308) described the G2 of T. joliveti as “plus développé” than the G 1 in the diagnosis of the genus, but her illustration of the gonopods of the holotype (reproduced in Fig. 98 E, G) shows that both are about the same size.

Guinot (1986: pl. 2C; see fig. 97D) illustrated a suture 2/3 of the thoracic sternum of Trogloplax as laterally interrupted with only the median part visible. This, however, is not the case as the lateral parts of suture 2/3, although shallow, are still visible ( Fig. 97 A, B).

Distribution. Indo-West Pacific region: Papua New Guinea.

Figures

FIGURE 93. Overall dorsal view of species of Australocarcinus and Trogloplax. A, Australocarcinus riparius, Australia: male 8.8 × 10.2 mm (ZRC 2006.167); B, A. riparius, Australia: female 9.0 × 11.3 mm (ZRC 2006.167); C, Australocarcinus kanaka, New Caledonia: female 8.5 × 9.8 mm (ZRC 2009.111); D, Australocarcinus palauensis, Palau: holotype female (5.8 × 7.1 mm) (USNM 277853); E, F, Trogloplax joliveti, New Britain: holotype male 16.0 × 21.0 mm (MNHN-IU- 2014 - 10457) (after Guinot 1986: pl. 1 A, B); G, Trogloplax joliveti, New Britain: male 15.7 × 18.6 mm (ZRC 2015.294); H, Trogloplax joliveti, New Britain: female 14.1 × 16.8 mm (ZRC 2015.295).

FIGURE 94. Frontal view and third maxilliped of species of Australocarcinus and Trogloplax. A, Australocarcinus riparius, Australia: male 8.8 × 10.2 mm (ZRC 2006.167); B, Australocarcinus kanaka, New Caledonia: female 8.5 × 9.8 mm (ZRC 2009.111); C, D, Australocarcinus palauensis, Palau: holotype female (5.8 × 7.1 mm) (USNM 277853); E, Trogloplax joliveti, New Britain: male 15.7 × 18.6 mm (MNHN-B 20136); F, Trogloplax joliveti, New Britain: female 14.1 × 16.8 mm (ZRC 2015.295); G, Australocarcinus riparius, Australia: holotype male (after Davie 1988: fig. 1 C); H, Australocarcinus kanaka, New Caledonia: paratype female 9.5 × 11.1 mm (after Davie & Guinot 1996: fig. 3 C); I, Australocarcinus palauensis, Palau: holotype female (5.8 × 7.1 mm) (USNM 277853) (after Davie & Guinot 1996: fig. 5 B); J, Trogloplax joliveti, New Britain: holotype male 16.0 × 21.0 mm (MNHN-IU- 2014 - 10457) (after Guinot 1986: pl. 2 B).

FIGURE 95. Chelae of species of Australocarcinus and Trogloplax. A, B, Australocarcinus riparius, Australia: male 8.8 × 10.2 mm (ZRC 2006.167); C, D, Australocarcinus kanaka, New Caledonia: female 8.5 × 9.8 mm (ZRC 2009.111); E, F, Australocarcinus palauensis, Palau: holotype female (5.8 × 7.1 mm) (USNM 277853); G, H, Trogloplax joliveti, New Britain: male 15.7 × 18.6 mm (ZRC 2015.294).

FIGURE 97. Male anterior thoracic sternum and pleon of Trogloplax joliveti, New Britain. A ‒ C, male 15.7 × 18.6 mm (ZRC 2015.294); D, E, paratype male 20.0 × 27.0 mm (MNHN-IU- 2014 - 10458) (after Guinot 1986: pl. 2 C, D). A ‒ D, male thoracic sternum and pleon; E, posterior part of sternum showing penis. Abbreviations: 4 ‒ 8 = thoracic sternites 4 ‒ 8, respectively; 4 / 5 - 7 / 8 = thoracic sternal sutures 4 / 5 - 7 / 8; b. p. = press button of male pleonal locking mechanism; c. s = margin of sterno-pleonal cavity; cx 4, 5 = coxa of P 4 and P 5, respectively; l. m = median line of sternum; p = penis; p. s = penis opening; s. s. = “ supplementary plate ”.

FIGURE 98. Gonopods of species of Australocarcinus and Trogloplax. A, B, Australocarcinus riparius, Australia: holotype male (after Davie 1988: fig. 1 A, B); C, D, Australocarcinus kanaka, New Caledonia: holotype male 9.5 × 11.1 mm (after Davie & Guinot 1996: fig. 4); E, F, Trogloplax joliveti, New Britain: paratype male 20.0 × 27.0 mm (MNHN-IU- 2014 - 10458) (after Guinot 1986: pl. 2 F, G); G ‒ J, Trogloplax joliveti, New Britain: male 15.7 × 18.6 mm (ZRC 2015.294). Scales: G, J = 1.0 mm; H, I = 0.5 mm.

FIGURE 99. Female pleon and vulvae of species of Australocarcinus and Trogloplax. A, B, Australocarcinus riparius, Australia: female 9.0 × 11.3 mm (ZRC 2006.167); C, D, Australocarcinus kanaka, New Caledonia: female 8.5 × 9.8 mm (ZRC 2009.111); E, F, Australocarcinus palauensis, Palau: holotype female (5.8 × 7.1 mm) (USNM 277853); G, H, Trogloplax joliveti, New Britain: female 14.1 × 16.8 mm (ZRC 2015.295). A, C, E, G, thoracic sternum with pleon; B, D, F, H, female sterno-pleonal cavity with vulvae.