Leptograpsodes Montgomery, 1931

Guinot, Danièle, Ng, Ngan Kee & Rodríguez Moreno, Paula A., 2018, Review of grapsoid families for the establishment of a new family for Leptograpsodes Montgomery, 1931, and a new genus of Gecarcinidae H. Milne Edwards, 1837 (Crustacea, Decapoda, Brachyura, Grapsoidea MacLeay, 1838), Zoosystema 40 (26), pp. 547-604 : 555-556

Genus Leptograpsodes Montgomery, 1931

Cyclograpsus H. Milne Edwards, 1837 : pro parte (only C. octodentatus p. 80).

Leptograpsodes Montgomery, 1931: 452 ; George 1962: 71; Bennett 1964: 81; Griffin 1969: 325; 1971: 598; Sternberg & Cumberlidge 1998: 125, 129, 130, 131, 134, figs 3, 5, table 3; Cuesta & Schubart 1999: 163; Schubart et al. 2001: 41; Davie 2002: 215; Poore 2004: 506; N. K. Ng 2006: 39; Ng et al. 2008: 217; De Grave et al. 2009: 44; Cuesta et al. 2011: 226; Schubart 2011: 473, 476; Ip et al. 2015: 217, 223; Davie et al. 2015b: 958.

TYPE SPECIES. — Cyclograpsus octodentatus H. Milne Edwards, 1837 by original designation. (senior synonym of Leptograpsodes webhaysi Montgomery, 1931 ).

GENUS MONOTYPIC. — Gender masculine.

DESCRIPTION

Carapace

Carapace broader than long, sub-hexagonal, with strongly convex lateral margins. One prominent tooth immediately behind orbital angle, and three weak teeth decreasing in size posteriorly, last obsolete. Dorsal surface not swollen, glabrous, markedly granulated on anterior part; two pairs of postfrontal lobes; a trace of oblique groove from first antero-lateral tooth; a pair of deep oblique lateral grooves about at level of second antero-lateral teeth, not reaching deep transverse groove; several striated ridges close to postero-lateral margins; a pair of two characteristics deep pits on each protogastric region.

Front rather wide, deflexed; anterior margin straight. Antennules transversely placed in deep fossae beneath the front. Antenna: basal article very broad, immobile, with a strong external expansion and a smaller internal, the fourth article being inserted in the concavity. Proepistome (interantennular septum) forming a broad triangle deeply inserted in lower frontal margin. Orbit bounded externally by pyramidal tooth that is the most anterior of the antero-lateral border. Supraorbital margins without trace of cleft. Eyestalks short. Suborbital spine three-sided, moderately large.Suborbital margin sunken (not dorsally visible), very faint, finely granulose, continuous from near base of marked orbital spine to near inner limit of orbit; suborbital ridge much more dominant, consisting of small, coalescent granules, extending laterally below and beyond orbit. Presence of stridulatory apparatus (also in females): pars stridens formed by cristiform suborbital ridge rubbing on P1 merus (plectrum). Epistomial margin coarsely granulated. Pterygostome with simple lateral groove, without supplementary groove. Subhepatic, pterygostomial and subbranchial regions covered by thick pubescence lacking distinct reticulate pattern.

Thoracopods

Mxp3 widely gaping, showing a rhomboidal gap between them; ischium much longer than merus and bearing fringe of hairs on both medial and lateral sides; merus trapezoid, not auriculate, narrower proximally than distally, with a not hairy sulcus, bordered by raised ridge that forms the entire internal margin; ischium with smaller ridge. Exopodite normal, not swollen or enlarged: narrow, slender and tapering, fringed with hairs, bearing flagellum.

Male chelipeds long, unequal, smooth, major chela becoming very robust at large size; coxa with small tufts of hydrophilic setae. Merus: at internal surface a whitish, smooth crest acting as the plectrum of the stridulatory apparatus, lost at largest sizes. Carpus with several teeth on inner margin. Palm smooth on outer surface, sparsely tuberculate on inner surface, without hairs on both surfaces. Fingers elongate, narrow, meeting subdistally and forming very narrow spoon at corneous tip, without brush of setae; fixed finger srongly bent downwards, with faint ridge; both occluding margins with rather strong teeth, grouped into strong lobe near base of fixed finger. Female chelipeds equal, narrower, fingers straighter, slightly gaping when closed; chela smooth on both surfaces.

Walking legs rather stout, flattened, P2 and P3 the longest and stoutest. No dense mat of setae on surface of articles and no fringes of setae for swimming ability; merus with transvese striations, without spines on posterior border; propodi with only very few and short spine-like setae; dactyli slender, long, slightly curved, with sparse short, black spine-like setae. Pouches of dense tufts of hydrophilic setae on P2-P4 coxae, thicker and longer on P3, P4.

Pleon

Male pleon with six free somites, widest at middle of laterally convex third somite; following somites narrowing uniformly to distal edge of sixth; somite 6 short, wide. Telson markedly narrower than somite 6.

Thoracic sternum

Thoracic sternum much widened; sternite 1 small, triangular, setiferous, visible between mxp3; sternite 2 rather high, dome-shaped; suture 1/2 convex, as complete, thickened ridge; suture 2/3 complete, thin but conspicuous, underlined by a row of dense setae; no suture 3/4, no trace, even lateral, of entire fusion of sternites 3, 4; sternite 4 short, with deeply hollowed lateral margin; sternite 3 + 4 wide, rather short, covered by dense short setae; on sternite 4 margin of the sterno-pleonal cavity marked by rim at level of telson; sutures 4/5, 5/6 interrupted; suture 6/7 interrupted but, at this level, a transverse ridge forming a thick triangular bridge superficially uniting the two halves of the sternal plate and extending forward to become the bottom of the sterno-pleonal cavity; suture 7/8 interrupted, much shorter than preceding sutures; episternites 4-6 vertically expanded, entirely delimited; sternite 7 much widened; episternite 7 horizontally expanded, delimited anteriorly by an incomplete sulcus; posterior emargination wide, concave, semicircular, reaching sternite 7; sternite 8 unexposed medially, only developed laterally, completely recovered by pleon when closed except for a very small proximal portion close to the P5 coxosternal condyle. Median line only on sternite 7, bumping into median bridge. Sterno-pleonal cavity wide, not deeply hollowed, only weakly inclined posteriorly.

Male gonopore and penis

Male gonopore sternal but very close to, seemingly joined to, the P5 coxa but in posteriormost location in relation to suture 7/8. Penis emerging just above P5 coxo-sternal condyle, and formed by cylindrical proximal portion passing between episternite 7 and sternite 8; in large male 51.8 × 68.3 mm as in the smaller male neotype 17.3 × 20.6 mm, when pleon is folded, penis has a small proximal portion (with different colouration) that is exposed, continues as a calcified cylindrical tube and then develops into a large papilla; a very small proximal part of sternite 8 is also exposed, these portions being covered at smallest size (but not visible in male 12.8 × 15.4 mm).

Pleonal-locking mechanism

Pleonal-locking mechanism effective: males with pair of two prominent, acute buttons on sternite 5, rather close to suture 4/5, not covered by gonopods situated more internally within sterno-pleonal cavity; on pleonal somite 6 deep socket posteriorly and defined by strongly calcified, V-shaped bor-der. Locking buttons still present in adult females, at least in specimen measuring 17.1 × 20.6 mm, but then lost.

Gonopods

G1 long, reaching suture 4/5, quite slender, weakly curved outwards distally; sternal surface with moderatly long groove towards medial surface ending in distal flap; lateral surface sparsely setose; medial surface with numerous setae extending from base to tip; a moderately dense tuft of setae at the tip almost concealing short, blunt, horny tip and flap on sternal surface ( Fig. 1F ). G2 very small.

Vulvae

Vulva in middle of sternite 6, very small, occluded by operculum.

Figures

FIG. 1. — Leptograpsodes octodentatus (H. Milne Edwards, 1837), ♂ 51.8 ×68.3 mm, South Australia, MNHN-IU-2013-14993 (ex NMV J55301-1): A, carapace, dorsal surface; B, chelipeds; C, thoracic sternum with pleon (setal tufts visible); D, thoracic sternum without pleon; E, genital area with male gonopore and penis; F, G1, two views; G, front, orbit, antenna (with articles 1-4 and flagellum) and suborbital ridge as pars stridens. Scale bars: 10 mm.