Leelumnus radium Mendoza & Ng, 2011, sp. nov.
Creators: name: Mendoza, Jose Christopher E.
name: Ng, Peter K. L.
Publisher: name: Zenodo
Year: 2011
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Pilumnidae
Leelumnus
Leelumnus radium

description: Leelumnus radium sp. nov.
(Figs. 1–3, 4 A, 5)
Material examined. Holotype male (18.1 × 11.6 mm) (ZRC 2011.0036), Paku Buoy, 01º23.539´N, 104º00.142´E, off Changi Point, coll. S.L.M. Teo et al., 15 Apr. 2010. Paratypes: 1 male (9.6 × 6.5 mm), 1 female (12.7 × 8.0 mm), 1 ovigerous female, (11.5 × 7.5 mm) (ZRC 2011.0037), Lek’s oyster farm, off northeastern Tekong Island, coll. S.L.M. Teo et al., 26 Aug. 2010; 1 male (12.6 × 8.5 mm), 1 female (10.0 × 6.9 mm) (ZRC 2011.0038), buoy, 01º14.679´N, 103º52.180´E, off eastern Sentosa Island, coll. S.L.M. Teo et al., 7 Jan. 2011; 7 males (7.1 X 6.0 mm - 16.3 X 10.5 mm), 8 females (7 ovigerous, 6.8 X 5.4 mm - 12.7 X 8.75 mm) (ZRC 2011.0039), 1 male, (9.8 X 6.7 mm) 1 ovigerous female (10.1 X 6.7 mm) (NHM), 1 male, (8.5 X 5.7 mm), 1 ovigerous female, (8.8 X 5.9 mm) (RMNH), Lek’s oyster farm, off northeastern Tekong Island, amongst encrusting community on submerged nets and ropes, coll. J.C. Mendoza & S.K. Tan, 28 Feb. 2011. All localities in Singapore.
Description of holotype. Carapace transversely subhexagonal, width 1.5–1.6 times length; regions poorly defined; dorsal surface convex, mostly smooth except for patches of minute granules on protogastric and mesobranchial regions, sparsely covered with long and short, plumose setae. Front moderately produced beyond orbits, divided into 2 lobes by V-shaped notch continuing posteriorly as narrow fissure reaching tip of proepistome ventrally; anterior margin of lobes gently concave, granulate, mesial angle more produced than lateral, lateral angle low, not distinctly separated from supraorbital margin; fronto-orbital region relatively narrow transversely, ca. 0.4 times maximum carapace width. Supraorbital margin entire but lined with small granules. Anterolateral margin granulate; exorbital angle low, not prominently projecting; rest of anterolateral margin with 4 distinct teeth; first tooth smallest, connected to exorbital angle by distinct, horizontal, granulate crest; subsequent teeth projecting laterally, curving anteriorly, second broadly triangular, third and fourth relatively more acute. Posterolateral margin almost straight to slightly sinuous, converging towards gently convex posterior carapace margin. Basal antennal article subrectangular, filling orbital hiatus; flagellum long. Antennules folding transversely; proepistome (interantennular septum) narrow. Orbits transverse, relatively short, rounded; eyes filling entire orbital space; distal part of short ocular peduncle covered with minute granules; cornea prominent, rounded. Infraorbital margin distinctly granulate, internal infra-orbital tooth projecting, triangular, visible from dorsal view. Suborbital, subhepatic, pterygostomial regions finely granulate.
Epistome well-produced; posterior border with acute median projection, with prominent notches laterally. Endostome with well-defined ridges forming channel for efferent water current with endopod of first maxillipeds. Third maxillipeds short, stout; merus quadrate, anterolateral angle rounded, not prominently produced, surface finely granular, especially along margins; palps long; ischium subrectangular, with shallow submedian sulcus; exopod stout, distal edge almost reaching anterior edge of merus, inner subdistal tooth prominent, with well-developed flagellum.
Thoracic sternum narrow, surface smooth to finely granulate, sparsely setose. Sternites 1, 2 fused; sternites 2, 3 completely separated by suture; sternites 3/4 partially fused, suture demarcated as deep lateral notches; sutures 4/5, 5/6 interrupted medially, 6/7, 7/8 complete; small median, triangular gap between sternites 6, 7. Median line on sternites 4, 6, 7, 8. Sternal press-button on sternite 5, near suture 4/5.
Chelipeds distinctly unequal. Inner margins of fused basis-ischium and merus granulate. External surface of carpus rugose, with rounded granules; inner distal angle produced as distinct tooth. Major chela robust; palm inflated, external surface smooth, glabrous; fingers distinctly shorter than palm; fixed finger deflexed, with larger teeth on cutting margin than those of dactylus; dactylus with shallow longitudinal groove on external surface. External surface of minor chela with 2 or 3 longitudinal rows of round granules, setose; fingers shorter than palm; fixed finger deflexed, with 2 longitudinal grooves on external surface, cutting edges with several low teeth.
Ambulatory legs moderately long, P3 longest, coxa-to-dactylus length subequal to maximum carapace width; setose, especially on carpus, propodus and dactylus. Articles relatively smooth, devoid of granules. Length of merus about 3.1 times width; distal end with distinct submedian, longitudinal notch, joining up with deep, transverse, subdistal groove. Dactylo-propodal locking mechanism present; distal propodal condyle large, rounded; corresponding tubercle on proximal end of dactylus small, truncatiform. Dactylus nearly straight, ending in a curved, chitinous claw.
Abdomen with all somites freely articulating, surfaces generally smooth, sparsely setose. Somite 6 subquadrate, lateral margins subparallel. Telson subtriangular, median length subequal to basal width; lateral margins almost straight, tip rounded, reaching level of coxo-sternal condyles of cheliped.
G1 sinuous, lateral edge lined with stiff, plumose setae; distal part distinctly flared, flattened, with numerous stiff, spiniform, simple setae. G2 short, sigmoid, about one-fifth length of G1. Penis short, papilliform, emerging from tip of swollen sternal condyle of P5 coxa.
Female morphology. Similar to that of the male in all non-sexual characters. The vulvae are relatively small and have a small sternal cover originating from the posterior margin. The anterior edge of the vulva does not reach sternal suture 5/6 (Fig. 4 A).
Colour. The background colour is dirty white with numerous patches of purple on the carapace and pereopods; fngers of chelipeds pink with purple base (Fig. 1).
Etymology. The specific epithet is derived from Radium, the 88th element on the periodic table of elements, to commemorate the occasion of Dr Lee Seng Tee’s 88th birthday in April 2011. The name is used as a noun in apposition.
Remarks. Leelumnus radium gen. et sp. nov., was collected from encrusting communities on floating and semi-submerged structures around Singapore. It has not been found in any other benthic habitats in Singapore as yet. Due to the volume of shipping that goes through Singapore, it is possible that this may even be an exotic species that has been transported via fouling communities on the hulls of ships or as larvae in ballast water (see Yeo et al. 2009, 2011).
description: Published as part of Mendoza, Jose Christopher E. & Ng, Peter K. L., 2011, Leelumnus radium, a new genus and species of pilumnid crab from marine encrusting communities in Singapore (Crustacea: Decapoda: Brachyura: Pilumnidae), pp. 58-66 in Zootaxa 2809 on pages 60-65, DOI: 10.5281/zenodo.201036