Singhaplax Serène & Soh, 1976

Castro, Peter, 2007, A reappraisal of the family Goneplacidae MacLeay, 1838 (Crustacea, Decapoda, Brachyura) and revision of the subfamily Goneplacinae, with the description of 10 new genera and 18 new species, Zoosystema 29 (4), pp. 609-774 : 711-713

Genus Singhaplax Serène & Soh, 1976

Ommatocarcinus – Tesch 1918: 186 (not Ommatocarcinus White, 1852 ).

Goneplax – Sakai 1939: 562 [in key], 563; 1976: 537 (part). — Balss 1957: 1656 (part). — Guinot 1969b: 520; 1971: 1081 (part). — Serène 1964: 189, 190; 1968: 89 (part); 1971: 915. — Serène & Umali 1972: 77 (part). — Dai et al. 1986: 376 (part). — Dai & Yang 1991: 406 (part).

Singhaplax Serène & Soh, 1976: 17 . — Karasawa & Kato 2003b: 140 [in list]. — Komatsu & Takeda 2003: 1243 [in list].

TYPE SPECIES. — Goneplax ockelmanni Serène, 1971 (by original designation; gender feminine).

SPECIES INCLUDED . — Singhaplax dichotoma n. sp.; S. ockelmanni ( Serène, 1971) ; S. orientalis ( Tesch, 1918) ; S. platypoda n. sp.; S. rhamphe n. sp.; S. styrax n. sp.; S. wolffi ( Serène, 1964) .

All species are restricted to the Indo-West Pacific region.

DIAGNOSIS. — Adults of small size (cw rarely more than 4.5 mm). Carapace ( Figs 35A ; 37 ; 38A ; 39A ; Tesch 1918: pl. 10, fig. 2, as Ommatocarcinus orientalis ; Takeda & Miyake 1968: fig. 7a, as Goneplax nipponensis ; Serène & Umali 1972: fig. 82, as G. ockelmanni ) transversely rectangular, much wider than long, relatively wider in larger individuals; widest at conspicuous outer orbital teeth; front slightly deflected ventrally, straight to slightly convex, not marked by median emargination. Notch between front, inner edge of supraorbital border; orbits wide, greatly expanded distally; supraorbital borders conspicuously sinuous, smooth; suborbital borders sinuous, inner tooth short or absent ( Tesch 1918: pl. 10, fig. 2a, as O. orientalis ); lateral borders sinuous, no anterolateral angle or tooth. Dorsal surface of carapace smooth, moderately convex, without clear indication of regions. Outer orbital angle with conspicuous, outwardly oriented, acute tooth; tooth placed medially or anteriorly on carapace. Basal antennal article short, distalmost (third) article does not reach front. Eye peduncles ( Figs 35A ; 37 ; 38A ; 39A ; Tesch 1918: pl. 10, fig. 2, as O. orientalis ; Takeda & Miyake 1968: fig. 7a, as G. nipponensis ; Serène & Umali 1972: fig. 82, as G. ockelmanni ) long, shorter or longer than front (0.8-1.2 front width); cornea elongated, spherical distal margin, not reniform (not conspicuously dorso-ventrally flattened, not clearly divided into anterior, posterior portions). No obvious stridulating mechanism other than possible rubbing of proximal portion of cheliped (P1) merus against pterygostomial ridge. Thoracic sternum wide. Median sulcus on thoracic sternite 4 absent; sutures 4/5, 5/6, 7/8 interrupted medially, 6/7 complete. Anterior end of sterno-abdominal cavity anterior to thoracic sternite 4. Cheliped fingers ( Fig. 37 ; Tesch 1918: pl. 10, fig. 2 d, as O. orientalis ) long, slender, shovel-like, slightly curved (strongly curved in large males), shorter than elongated propodus; dactylus without dark portion; inner (ventral) margin of propodus smooth or with low tubercles in large males; carpus without defined tooth on inner margin; merus with conspicuous tubercles on outer (dorsal) margin, long simple setae. Dorsal margins of ambulatory leg (P2-P5) meri ( Fig. 37 ) unarmed; dactyli of ambulatory legs slender, with carina on each side, setose (P5 propodus, dactylus of S. platypoda n. sp. broad, flat; Fig. 37 ). Male abdomen ( Fig. 36A ; Tesch 1918: pl. 10, fig. 2e, as O. orientalis ; Serène & Umali 1972: fig. 85, as G. ockelmanni ; Serène & Soh 1976: fig. 15A) with 6 freely-movable somites plus telson, wide (more slender in S. styrax n. sp.), somites 4-6 gradually decreasing in width from somite 3 (widest somite). Telson wide, slightly wider than long (slightly longer than wide in S. dichotoma n. sp., S. platypoda n. sp., and S. stryrax ). Somite 3 covers space between P5 coxae, somite 2 narrower than somite 3; somites 1, 2 leave small portion of thoracic sternite 8 visible. G1 ( Figs 35B ; 36B ; 38B ; 39B ; 40A ; Takeda & Miyake 1968: fig. 7d-f, as G. nipponensis ; Serène & Umali 1972: figs 86, 87, as G. ockelmanni ; Serène & Soh 1976: fig. 15B, B’) long, slender, or stout; slightly sinuous, slightly broadened proximally. G2 ( Figs 35C ; 36C ; 38C ; 39C ; 40B ; Tesch 1918: pl. 10, fig. 2 e, as O. orientalis ; Serène & Umali 1972: figs 88, 89, as G. ockelmanni ; Serène & Soh 1976: fig. 15C) slender, slightly longer than or as long as G1, flagellum longer than proximal part (peduncle); tip curved, pointed, or slightly enlarged with terminal spinule. Penis arising from P5 coxa, moderate size; broad, soft proximal expansion. Female abdomen with 6 freely-movable somites, wide.Telson much wider than long. Somite 3 covers space between P5 coxae, somite 2 slightly narrower than somite 3; somites 1, 2 leave small portion of thoracic sternite 8 visible. Vulva of two mature females reliably identified as belonging to genus ( S. styrax n. sp. and S. wolffi ) relatively large, extending from edge of suture 5/6 (displaced, arched to make contact with suture 4/ 5 in S. styrax n. sp.; slightly arched in small S. wolffi female) to median portion of thoracic sternite 6, vulvar cover absent.

REMARKS

Serène & Soh (1976: 17) described their new genus Singhaplax to include two Indo-West Pacific species that did not conform to the description of Goneplax sensu lato: G. nipponesis Yokoya, 1933 , and G. ockelmanni Serène, 1971 . Guinot (1969b: 522) had previously questioned the inclusion of G. nipponensis (= Singhaplax styrax n. sp.) in the genus Goneplax since its description did not give enough information on the ventral surface. Serène (1971: 915) and Serène & Umali (1972: 82) also commented that S. ockelmanni (as Goneplax ockelmanni ) was not congeneric with another species of Goneplax sensu lato ( G. sinuatifrons Miers, 1886 = Hadroplax sinuatifrons n. comb.) on account of the structure of their antennules and G1.

The discovery of additional species of Singhaplax has provided the opportunity to further characterize the genus. It is nearly identical to Microgoneplax n. gen. in terms of the shape of the carapace but it differs from the latter by the presence of a long G2 that is as long as or slightly longer than the G 1 in contrast to Microgoneplax n. gen., where the G2 is much shorter than the G1 (see description of Microgoneplax n. gen. below). A long G2 was the key character used by Serène & Umali (1972) to define Singhaplax . Other characters that separate Singhaplax from Goneplax sensu stricto and the five Indo-West Pacific genera that include species that were formerly included in Goneplax sensu lato are summarized in Table 4.

There are seven described species of Singhaplax , including four being described herein. Two yet undescribed species have been recently discovered in the Philippine Is and will be described jointly with T. Naruse.

Figures

FIG. 35. — Singhaplax dichotoma n. sp.,♂ holotype,cl 4.0 mm, cw 6.1 mm, Kai Is, Indonesia,KARUBAR,stn DW 29 (MNHN-B 30069): A, dorsal surface of the carapace; B, left G1, ventral view; C, right G2, ventral view. Scale bars: A, 5 mm; B, C, 1 mm.

FIG. 37. — Singhaplax platypoda n. sp.,pre-adult ♀ paratype,cl 3.3 mm,cw 6.0 mm,Futuna I., MUSORSTOM 7, stn DW 495 (MNHN-B 30068).

FIG. 38. — Singhaplax rhamphe n. sp., ♂ holotype, cl 4.4 mm, cw 7.6 mm, Kai Is, Indonesia, KARUBAR, stn DW 29 (MNHN-B 30071): A, dorsal surface of the carapace; B, left G1, ventral view; C, right G2, ventral view. Scale bars: A, 5 mm; B, C, 1 mm.

FIG. 39. — Singhaplax styrax n. sp., ♂ holotype, cl 4.1 mm, cw 6.7 mm, Kai Is, Indonesia, KARUBAR, stn DW 18 (MNHN-B 29211): A, dorsal surface of the carapace; B, left G1, ventral view; C, left G2, ventral view. Scale bars: A, 5 mm; B, C, 1 mm.

FIG. 36. — Singhaplax platypoda n. sp., ♂ holotype, cl 2.8 mm,cw 5.1 mm,Kai Is, Indonesia,KARUBAR,stn DW 22 (MNHN-B 29215): A, abdomen; B, right G1, ventral view; C, right G2, ventral view. Scale bars: A, 2 mm; B, C, 1 mm.

FIG. 40. — Singhaplax wolffi (Serène, 1964), ♂, cl 2.6 mm, cw 5.2 mm,north of New Caledonia,BATHUS 4,stn DW 896 (MNHN-B 29251): A, right G1, ventral view; B, right G2, ventral view. Scale bars: A, B, 0.5 mm.