Selatium elongatum ( A. Milne-Edwards, 1869 )

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 : 10

Selatium elongatum ( A. Milne-Edwards, 1869)

( Figs. 5–8 )

Sesarma elongatum A. Milne-Edwards, 1869: 30 (type locality: Madagascar). — Vannini & Valmori 1981: 83 ( Somalia). — Vannini et al. 1997 ( Kenya).

Sesarma elongata — De Man 1887: 645 (no new locality). — De Man 1892: 256 (description of type specimen). — Ortmann 1894: 56 ( Tanzania).

Sesarma latifemur Alcock, 1900: 421 (Andaman Islands) . — Alcock & McArdle 1903: pl. 66, fig. 2 (Andaman Islands).

Sesarma (Holometopus) elongata — Tesch 1917: 149 (no new locality). — Tesch 1918: 109 –112, pl. 5, fig. 2 (New Guinea, Ceram).

Sesarma (Holometopus) latifemur — Tesch 1917: 168 (no new locality).

Sesarma sp. — Fourmanoir 1954: 3 ( Madagascar).

Sesarma (Holometopus) elongatum — Crosnier 1965: 49, figs. 63–67, 72, 84, pl. 4 fig. 1. — Serène 1968: 107 (no new locality).

Selatium elongatum — Hartnoll 1975: 305 ( Tanzania). — Cannicci et al. 1999: 335 ( Kenya). — Fratini et al. 2005: 222 ( Kenya). — Schubart et al. 2006: 195 ( Kenya). — Ng et al. 2008a: 223 (list).

Material examined. Madagascar: Lectotype male (34.4 x 36.2 mm) (MNHN-B3640).

Kenya: Mida Creek, 1 male (33.9 x 35.3 mm), 1 female (33.0 x 33.2 mm) ( ZRC 2000.1782), coll. M. Vannini, November, 1991. Philippines, Boho l: 1 male ( ASIZ 72929), mangroves, Loboc River, coll. H.-C. Liu, 21 February 2003 ( DNA voucher); 4 males, 3 females ( ZRC 2004.0472), mangroves, Loboc River, coll. P. K. L. Ng et al., 2 March 2004; 1 male ( ZRC 2008.0713), station M19, Suncolan, Panglao, coll. P. K. L. Ng, 10 June 2004. Indonesia, Sulawesi: Tomini Bay: mangrove between Mapane and Poso, 1 male (40.1 x 40.9 mm), 1 juvenile female (24.6 x 24.7 mm) ( ZRC 2000.1738), coll. C. D. Schubart et al., 20 January 2000 ( DNA voucher); 4 males, 3 females, mangrove forest, on trees, Bunaken Island, off Manado, coll. N. K. Ng & J. Lai, September 2003. Papua New Guinea: 1 male (40.7 x 42.0 mm) ( ZRC 2009.0567), Oro Province, Tuti District, Tuti Wharf, on rope, coll. H. H. Tan, 10 December 2008.

Type locality. Madagascar.

Diagnosis. Carapace longitudinally rectangular, longer than wide; lateral margins subparallel or gently diverging towards posterior margin, entire, without epibranchial tooth, with only small notch marking rudimentary tooth ( Fig. 5 A, B); chelipeds unequal in adult males ( Fig. 5 A); chela with relatively short fingers ( Fig. 6 B); dorsal margin of palm with curved pectinated crest consisting of 43–48 teeth ( Fig. 7 A); dorsal margin of dactylus with row of 32–35 prominent tubercles ( Fig. 7 B); ambulatory legs relatively short ( Fig. 5 A); anterior thoracic sternites and male pleon relatively long longitudinally ( Figs. 6 A, 8C); distal part of G1 appears swollen, with short triangular pectinated tip ( Fig. 8 D–G).

Remarks. In naming this species, A. Milne Edwards (1869) did not state how many specimens he had nor did he select a holotype. As such, all his material must be regarded as syntypes. No subsequent author has selected a type specimen. We hereby designate the MNHN dried specimen (MNHN-B3640) (the only one that is still extant) as the lectotype of Sesarma elongatum . The material we have on hand from Madagascar to Sulawesi is clearly conspecific and we can find no significant morphological or genetic differences between them.

Ecology. Selatium elongatum is a tree-climbing species from mangroves. Hartnoll (1975) states that it can also be found sheltering beneath rocks and mentions that Fourmanoir (1954) records it from pools at the high water mark in Madagascar. However, we could not find this record by Fourmanoir despite careful reading of that source. The present specimens from Sulawesi were found in mangrove tree holes or climbing along the trunk slightly above sea water level. Cannicci et al. (1999) indicated that in Kenya this species is active at high tide and feeds on floating algae and mangrove leaves. These authors also found that males defend their activity areas from other large males. This explains the marked sexual dimorphism in cheliped size of this species, with prominent male chelae.

Figures

FIGURE 5. Selatium elongatum (A. Milne-Edwards, 1869). Lectotype male (34.4 x 36.2 mm) (MNHN-B 3640), Madagascar. A, dorsal view; B, dorsal view of carapace; C, anterior thoracic sternum and abdomen.

FIGURE 6. Selatium elongatum (A. Milne-Edwards, 1869). Male (40.1 x 40.9 mm) (ZRC 2000.1738), Tomini Bay, Sulawesi. A, anterior thoracic sternum and abdomen; B, outer view of right chela.

FIGURE 7. Selatium elongatum (A. Milne-Edwards, 1869). Male (40.1 x 40.9 mm) (ZRC 2000.1738), Tomini Bay, Sulawesi. A, dorsal view of pectinated ridge on palm; B, ridge on dactylus of chela.

FIGURE 8. Selatium elongatum (A. Milne-Edwards, 1869). Male (40.1 x 40.9 mm) (ZRC 2000.1738), Tomini Bay, Sulawesi. A, abdomen; B, left 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).