Selatium brockii (De Man, 1887 )

Schubart, Christoph D., Liu, Hung-Chang & Ng, Peter K. L., 2009, Revision of Selatium Serène & Soh, 1970 (Crustacea: Brachyura: Sesarmidae), with description of a new genus and two new species, Zootaxa 2154, pp. 1-29 : 4-10

Selatium brockii (De Man, 1887)

( Figs. 1–4 )

Sesarma brockii De Man, 1887: 651 (type locality: Ambon). — De Man 1888: 373–377, pl. 16 fig. 3 ( Ambon). — Thallwitz 1891: 39 ( Ternate). — Ortmann 1894: 721 (Pacific). — Alcock 1900: 421 (Andaman Islands).

Sesarma (Episesarma) brockii — De Man 1895: 171 (Kalimantan: Pontianak). — Nobili 1901: 3 ( Sarawak).

Sesarma (Sesarma) brockii — Nobili 1900: 507 ( Malaya). — De Man 1902: 516 (Halmahera). — Nobili 1903: 26 (Kalimantan: Samarinda). — Tweedie 1936: 50 ( Singapore).

Sesarma ( Sesarma s.s.) brockii — Tesch 1917: 139 –140 (New Guinea).

Sesarma (Sesarma) brocki — Serène 1968: 106 (list).

Sesarma brocki — Vannini et al. 1997 ( Kenya).

Neoepisesarma (Selatium) brocki — Serène & Soh 1970: 397 (no new locality).

Selatium brocki — Hartnoll 1975: 305 ( Tanzania). — Tan & Ng 1988: 98 ( Singapore). — Tan & Ng 1994: 82 ( Singapore, Malaysia).

Selatium brockii — Sivasothi et al. 1993 ( Singapore). — Sivasothi 2000 ( Singapore). — Fratini et al. 2005: 222 ( Kenya). — Schubart et al. 2006: 195 ( Kenya). — Ng et al. 2008a: 223 (list). — Ng et al. 2008b: 73, 74 ( Singapore).

Material examined. Kenya: Mida Creek, 1 female (17.55 x 15.65 mm) ( ZRC 2000.1786), coll. M. Vannini, 1991. Thailand: Phuket: Ao Tang Khen mangrove, 1 male (12.7 x 11.4 mm) ( ZRC 2000.1897), coll. C. D. Schubart et al., 22 August 1999 ( DNA voucher). Singapore: Seletar: Kg. S. Pus, 1 ovigerous female (22.4 mm) ( ZRC 1964.9.25.358), coll. M. W. F. Tweedie, 1950; Johor Straits, 1 male (26.7 x 24.65 mm) ( ZRC 1968.11.10.1), coll. C. L. Soh, 10 November 1969; Mandai mangroves, 1 male (29.2 x 26.9 mm) ( ZRC 1989.2875), coll. K. Lim & Y. H. Koo, 31 October 1989; same locality, 2 males ( ZRC 2009.0565), coll. C. D. Schubart et al., 10 September 1999; same locality, 1 male ( MZUF 2497), coll. N. Sivasothi, L. Morino & C. Barelli, 11 September 1999 ( DNA voucher); Sungei Buloh mangroves, 1 female (15.2 mm), 3 juveniles ( ZRC 2009.0566), coll. C. D. Schubart & N. Sivasothi, 16 August 1999; Tuas, Raffles Marina, 1 male ( ZRC 2000.2537), coll. H. H. Tan, 21 October 2000; Labrador Beach, 1 male (10.96 x 9.64 mm) (SMF-33841), coll. C. D. Schubart, S. Klaus & P. Koller, 19 March 2006 ( DNA voucher). Indonesia, Western New Guinea: 1 male ( ZRC 2000.2071), Tipoeka River, coll. D. L. Rahayu, 25 January 2000; 1 female ( ZRC 2003.0489), Ajkwa, coll. D. L. Rahayu, 22 September 2001; 1 male ( ZRC 2003.0490), station A Is/I/A, Ajkwa, coll. D. L. Rahayu, 9 October 2002; 1 juvenile female ( ZRC 2003.0491), station K Is/III/C, Kamora, coll. D. L. Rahayu, 21 October 2002; 1 male, 1 female ( ZRC 2003.0492), station K Is/III/C, Kamora, coll. D. L. Rahayu, 6 November 2002; 2 females ( ZRC 2003.0493) station K Is/III/A1, Kamora, coll. D. L. Rahayu, 20 November 2002. Philippines, Bohol: 2 males, 4 females (2 ovigerous) ( ZRC 2004.0471), mangroves, Loboc River, coll. P. K. L. Ng et al., 2 March 2004. Fiji: Viti Levu, Nadi Bay, above strand line under rock, 1 juvenile female (13.6 x 12.5 mm) ( ZRC 2002.0157), coll. G. Paulay, November 1996; Micronesia, Ponape (= Pohnpei): 1 male (16.3 x 14.9 mm) ( ZRC 2002.0156), coll. G. P a u l a y.

Type locality. Ambon ( Indonesia).

Diagnosis. Carapace quadrate, wider than long; lateral margins gently diverging towards posterior margin, prominent sharp epibranchial tooth ( Fig. 1 A, B); chelipeds equal to subequal in males ( Fig. 1 A); chela and fingers relatively long ( Fig. 2 C); dorsal margin of palm with curved pectinated crest consisting of 37–39 teeth ( Fig. 3 A, B); dorsal margin of dactylus with row of 21–23 prominent tubercles ( Fig. 3 C); ambulatory legs relatively long ( Fig. 1 A); anterior thoracic sternites and male abdomen relatively short longitudinally ( Figs. 2 A, 4C); distal part of G1 dilated with distinct triangular pectinated tip ( Fig. 4 D–G).

Description. Carapace quadrate, lateral margins slightly diverging posteriorly; dorsal surfaces relatively smooth, regions well defined by prominent grooves; surface adjacent to anterolateral margins lined with strong, oblique striae; gastrocardiac surface with distinct groove. Postfrontal lobes prominent; 2 median lobes larger, with granular ridge just anterior to it; 2 lateral lobes with uneven margins; lobes separated by deep grooves. Front strongly deflexed downwards, with 2 prominent subtruncate lobes separated by broad, deep cleft, strongly produced anteriorly. Supraorbital margin entire. Anterolateral margin entire, confluent with posterolateral margin, with prominent epibranchial tooth, minute tubercle as rudiment of subsequent tooth. Posterolateral margin gently diverging towards weakly convex posterior carapace margin. Epistome with pronounced horizontal ridge, medially concave; posterior margin with prominent median triangular projection, lateral part with 2 concave indentations. Verwey’s groove delimited by dorsal and ventral rows of setae. Infraorbital ridge tuberculate, setose. Pterygostomial region weakly granular, covered by dense surface of distally curved setae. Antenna entering orbit; basal segments of antenna, antennule not separated by septum; basal antennal segment mobile. Ischium of third maxilliped with shallow submedian sulcus; merus bovate with distinct submedian longitudinal setose ridge extending to antero-external angle of ischium; exopod slender, with long flagellum.

Chelipeds equal to subequal in size and shape in adult males. Outer surface of chelae distinctly granular, inner surface with coarser granules, low submedian transverse ridge of granules closer to fingers; ventral border gently convex to straight; dorsal margin of palm with longitudinal crest of 25–27 low proximal granules, followed by slightly curved pectinated crest consisting of 37–39 teeth of varying sizes, median ones higher; scattered tubercles on inner side; fingers more than half length of palm; dorsal margin of dactylus with row of 21–23 tubercles, proximal ones rounder, otherwise transversely elongate with conical apex; cutting edge of dactylus with several teeth on distal two-thirds, distal one largest; cutting edge of pollex with several teeth, median and subdistal ones largest; tips of fingers hoofed (medially excavated) with sharp cutting edges. Outer surface of carpus rugose; inner distal angle produced, margins with sharp tubercles. Outer face of merus strongly convex, with rows of granules; inner face granular, strongly expanded distally forming foliaceous structure, with subdistal tooth on dorsal margin, distal margins lined with numerous large, sharp spines and teeth, distal part visible from dorsal view, even when chelipeds apposed tightly against carapace; inner face with 2 longitudinal rows of stiff setae. Basis, ischium immobile but separated by distinct suture, surface with scattered granules.

Ambulatory legs long, third pair longest. Coxae of ambulatory legs 1–3 with short setae around lateral margins, without tufts of long setae on ventral and lateral surfaces. Outer surfaces of meri, carpi, propodi rugose. Meri laterally flattened, foliaceous, margins finely granulated; with distinct subdistal dorsal spine; outer part of postero-distal margin expanded, anterior surface convex. Outer surface of carpi with 2 distinct carinae, 1 on inner surface. Distal third of propodi with short, stiff setae dorsally and ventrally; lower distal margins each with 4 or 5 short spines. Dactylo-propodal lock absent but propodal-dactylar condyle prominent. Dactyli very short, ca. one-third length of propodus, with 4 rows of setae.

Margins of anterior thoracic sternites and surfaces of sternites 1–4 setose. Sternites 1, 2 completely fused, suture concave toward buccal cavity; suture 3/4 separated by complete suture; sutures 4/5, 5/6, 6/7, 7/8 medially interrupted, separated by wide gap; deep longitudinal median groove present on sternites 7, 8; male sterno-abdominal cavity not reaching suture 3/4; sternite 8 not visible when male pleon fully closed. Penis proximally calcified, sternal. Abdomen triangular; lateral margins of abdominal somites 3, 6 convex, lateral margins of somites 4, 5 gently concave. Telson subcircular, slightly longer than wide, tip rounded. G1 very stout, distal part dilated, distinctly wider than median part, giving structure gently curved appearance from ventral view; distal part with short, triangular pectinated structure. G2 very short, distally spatuliform, no distal segment present.

Female. Chela generally smaller, pectinated crest on palm of cheliped replaced by tubercles.

Remarks. De Man (1887) briefly diagnosed this species without figures from a 26 by 23 mm male collected from Ambon in Indonesia. He subsequently provided a detailed description and excellent figures of the same specimen (De Man 1888). We have not been able to locate this specimen; it is not to be found in any of the repositories De Man was known to have deposited his material (see Fransen et al. 1997), and like much of the material from his 1887–1888 report, is almost certainly lost. We have also not been able to find another specimen from Ambon. The detailed description and figures of De Man (1888), however, leave no doubt that our material belongs to this species. Since all the material we have examined from Kenya to the western Pacific is referable to one species and we have not seen any morphological or clearcut genetic data to suggest otherwise, we also do not see the immediate need to designate a neotype for it.

Ecology. Selatium brockii is a tree-climbing species from coastal mangroves. It is most commonly found underneath the bark of dead trunks or inside hollow trees in Southeast Asian mangroves. The ecology of this species has been discussed at length by Sivasothi et al. (1993) and Sivasothi (2000).

Figures

FIGURE 1. Selatium brockii (De Man, 1887). Male (29.2 x 26.9 mm) (ZRC 1989.2875), Mandai, Singapore. A, dorsal view; B, dorsal view of carapace; C, frontal view of carapace.

FIGURE 2. Selatium brockii (De Man, 1887). Male (29.2 x 26.9 mm) (ZRC 1989.2875), Mandai, Singapore. A, anterior sternum and abdomen; B, right propodus and dactylus of first ambulatory leg; C, outer view of right chela.

FIGURE 3. Selatium brockii (De Man, 1887). Male (29.2 x 26.9 mm) (ZRC 1989.2875), Mandai, Singapore. A, lateral view of pectinated ridge on dorsal margin of palm; B, dorsal view of pectinated ridge on dorsal margin of palm; C, ridge on dorsal margin of dactylus.

FIGURE 4. Selatium brockii (De Man, 1887). Male (29.2 x 26.9 mm) (ZRC 1989.2875), Mandai, Singapore. A, abdomen; B, right third maxilliped (denuded); C, left side of anterior thoracic sternum; D, dorsal view of left G 1 (denuded); E, ventral view of left G 1 (denuded); F, dorsal view of distal part of left G 1 (denuded); G, ventral view of distal part of left G 1 (denuded); H, left G 2 (denuded).