Perisesarma dusumieri, (H. MILNE EDWARDS, 1853)

PERISESARMA DUSUMIERI (H. MILNE EDWARDS, 1853) View in CoL

( FIGS 3E View Figure 3 , 4E View Figure 4 , 5E View Figure 5 , 6E View Figure 6 , 7E View Figure 7 , 8E View Figure 8 , 9E View Figure9 , 10E View Figure 10 , 11E View Figure 11 , 14 View Figure 14 )

Sesarma dusumieri View in CoL (sic) H. Milne Edwards, 1853: 185.

Sesarma dussumieri – Targioni-Tozzetti, 1877: 145; De Man, 1888: 177; Campbell, 1967: 4 (in key).

Sesarma bidens View in CoL – Kingsley, 1880: 215 (see label in Fig. 14F View Figure 14 in the present study).

Sesarma (Perisesarma) dussumieri – De Man, 1895: 208.

Sesarma (Chiromantes) dussumieri – Tesch, 1917: 146; Tweedie, 1936: 66.

Chiromantes dussumieri – Tan & Ng, 1994: 82 (in list)

Perisesarma dussumieri – Ng et al., 2008: 222 (in list); Davie, 2010: 204 (in key); Shahdadi & Schubart, 2015: 1082 (in Table 1).

Material examined: The examined material is listed in Table 1. A single dry male specimen (carapace width = 31.60 cm) in the Muséum National d’Histoire Naturelle, Paris, France ( MNHN IU 2000-10963 ) from India, Bombay is considered to be the holotype ( Table 1, S624). If it turns out to be part of a type series, it will be designated as lectotype (D. Guinot, personal information) .

Redescription: A small to medium sized crab (up to about 3.4 cm carapace width in studied material). Carapace squarish, greatest width between exorbital angles, slightly broader than long (about 1.15 times broader than long), front c. 0.51 times carapace width, deflexed, with shallow median invagination, carapace regions distinguishable, postfrontal region with four lobes of almost equal width, separated by shallow furrows, gastric region distinct, lateral surface lined with oblique striae, anterolateral margin with small epibranchial tooth, lateral margin slightly concave, lined with row of short setae ( Fig. 14A, B, F View Figure 14 ).

Chelipeds subequal. Merus with posterior border granulate and small subdistal spine, lower border granulate, anterior border granulate with distinct subdistal spine. Carpus with inner and outer margins granular and dorsally rough. Chelae proportionally large and robust, palms with two oblique pectinated crests on the upper surface, followed by 2–4 small tubercles (with chitinous peak) on inner side, proximal crest with 11–14 tall teeth, shorter than in distal crest with 13–17 tall teeth ( Figs 3E View Figure 3 , 4E View Figure 4 ), outer surface of palm coarsely granulated ( Fig. 14C View Figure 14 ), inner surface of palm with several granules bearing chitinous peaks ( Fig. 14D View Figure 14 ), ventral surface with coarse granules with chitinous tip over entire length ( Fig. 14D View Figure 14 ), length of cutting edge 0.35 times length of propodus. Chela dactylus with 11–13 broadly oval, low but distinct tubercles on dorsal surface ( Fig. 14C View Figure 14 ), most tubercles have transverse row of chitinous granules (3–6 granules), enlarged chitinous granules on inner side of dorsal surface of dactylus ( Fig. 14E View Figure 14 ). Fingers with tips chitinous, cutting edges with small and large teeth, leaving no gap when closed in adult males and with tufts of long, coarse setae on inner side ( Fig. 14C, D View Figure 14 ).

Walking legs ( Fig. 14A, F View Figure 14 ) relatively long. Third pair longer than others (about 1.9 times carapace width), merus flattened, relatively broad (about 2.2 times as long as wide), propodus relatively broad (about 2.3 times as long as wide), dorsal and ventral margins with dense brush-like stiff setae.

Male pleon relatively long, triangular, somites 1 and 2 very narrow, somite 3 widest, with lateral margins strongly convex, somite 4 more trapezoidal than somite 5, somite 6 considerably elongated and more hexagonal than trapezoidal, with a shallow concavity between somites 5 and 6, telson small, longer than basal width ( Figs 5E View Figure 5 , 6E View Figure 6 ) ( Table 4). The male press button is proportionally large ( Fig. 7E View Figure 7 ).

G1 ( Fig. 8E View Figure 8 ) relatively stout, with thick base, apical process short, truncated, slightly bent to form an angle about 50° with vertical axis, arched in cross section with syncline towards lateral surface, aperture terminal. G2 short, narrow, basal part wider (3 times wider than apical part), bent to form angle of about 140°.

Females with proportionally smaller chelipeds, smaller and less prominent dactylar tubercles. Pectinated crests vestigial or absent. Walking legs less setose compared to males. Pleon broadened, telson triangular, wider than long, inserted into somite 6 with less than half of its length ( Fig. 9E View Figure9 ). The vulvae are completely positioned on sternite 5, with operculum in inner part, accompanied by a large sternal cover anteriorly ( Fig. 10E View Figure 10 ).

Distribution: Bombay, India (type locality) (H. Milne Edwards, 1853); Mergui Archipelago ( Myanmar), mainland Myanmar and Penang ( Malaysia) ( De Man, 1888, 1895); Singapore ( Tweedie, 1936; Tan and Ng 1994); Malacca ( Malaysia), Phuket ( Thailand) and Kerala, India (present study).

Remarks: According to the wide distribution range of this species from Bombay to Singapore, a morphological and genetic comparative study, examining the material from all over its geographic distribution, can significantly improve our understanding of the diversity and phylogeography of the taxon.