Parasesarma plicatum Latreille 1803
Creators: name: Rahayu, Dwi Listyo
name: Ng, Peter K. L.
Publisher: name: Zenodo
Year: 2010
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Sesarmidae
Parasesarma
Parasesarma plicatum

description: Parasesarma plicatum (Latreille, 1803)
(Figs. 1–4)
Cancer quadratus Fabricius, 1798: 341. – Zimsen 1964: 650.
Ocypode quadrata — Bosc 1802: 198.
Ocypoda plicata Latreille, 1803: 47.
Sesarma quadrata — H. Milne Edwards, 1837: 75. – H. Milne Edwards 1853: 183. – Hilgendorf 1878: 809. – De Man 1887: 655, 683, pl. 17, fig. 2. – Henderson 1893: 392. – Nobili 1903: 22.
Sesarma (Parasesarma) plicata — Tesch 1917: 187.
Parasesarma plicatum — Naiyanetr 2007: 114. – Ng & Davie, 2002: 379 – Ng et al. 2008: 222.
Sesarma aspera — Heller 1865: 63, pl. 6, fig. 1.
Sesarma quadratum — Miers 1879: 490. – Alcock 1900: 413.
Sesarma aspera — Müller 1887: 476 (not Sesarma aspera Heller, 1865).
Sesarma (Parasesarma) plicatum – Serène 1968: 107.
Types: Cancer quadratus Fabricius, 1793: lectotype (herein designated), male (21.0 x 17.0 mm) (ZMUC 2658), 1 male (17.0 x 14.0 mm) (ZMUC 2659), 1 female (18.0 x 14.0 mm) (ZMUC 2661), 1 female (15.0 x 13.0 mm) (ZMUC 118-4), 1 female (13.0 x 12.4 mm), Daldorff collection.
Material examined. 1 male (carapace damaged) (ZRC 1969.1.4.1), 1 male (carapace damaged) (ZRC 1969.1.4.2), 2 males (20.2 x 15.9 mm, 14.5 x 10.4 mm), 1 female (26.0 x 19.9 mm) (ZRC 1969.1.4.3), Bombay, India, coll. C. Chhapgar, 1968. – 4 males (18.5 x 14.4 mm, 14.9 x 12 mm, 7.9 x 5.0 mm, 7.0 x 4.5 mm), 1 female (6.3 x 4.5 mm) (ZRC 2001.850), Vellar Estuary, Porto Novo, Tamil Nadu, southern India, coll. N. K. Ng, 23 March 2001. – 15 males (10.6 x 7.8 – 22.8 x 17.5 mm), 7 females (14.0 x 11.0 – 19.4 x 14.8 mm) (ZRC 2000.1913), Phichai Fishport, Ao Nam Bor mangroves, Phuket, western Thailand, coll. C. D. Schubart & J. Lai, August 1999 – 7 males (13.0 x 9.7 – 20.3 x 15.7 mm) (ZRC 2008.0816), 4 males (15.8 x 13 – 21.9 x 17.8 mm), 1 female (19.1 x 15.5 mm), 1 ovigerous female (17.1 x 13.7 mm) (MZB), Teluk Kombal, Lombok Island, Indonesia, 7 April 2008, 8 June 2009.
Comparative material. Parasesarma exquisitum Dai & Song, 1986, holotype, male (13.6 x 10.0 mm) (IOZ CB 03317), Longmen, Qingzhou, Guangxi Autonomous Region, coll. 13 May 1980. Parasesarma aff. plicatum, 14 males (6.0 x 5.0 mm – 24.6 x 18.8 mm), 12 females (7.9 x 5.2 – 21.8 x 16.2 mm), Shatt Al- Basrah, Iraq (ZRC 2009.0797); 3 males (24.0 x 18.5; 19.8 x 15.5 x 18.3 x 13.7 mm), Khur Al-Zubair, Iraq (ZRC 2009.0798); all collected 2009.
Diagnosis. Carapace 1.35 times broader than long (Figs. 1 A, 2A, B, 3A); mesogastric, cardiac regions well defined; lateral carapace surface lined with strong oblique striae; carapace surface with sparsely scattered tufts of setae, lateral margins with short setae. Postfrontal margin with 4 distinct, similar lobes, separated by narrow grooves. External orbital tooth triangular, directed upward, fused with entire lateral carapace margin; greatest width of carapace at external orbital tooth.
Chelipeds subequal, large, robust (Fig. 2 C, 3D). Merus with outer margin tuberculate, with subdistal spine; inner margin tuberculate ending in large subdistal spine; outer surface striated, inner surface with longitudinal row of setae, scattered setae near upper margin. Carpus with inner angle not produced, outer margin, across dorsal surface striated. Upper surface of palm with 2 transverse pectinated crests (Fig. 3 E). Primary crest composed of 8–12 broad teeth. Secondary crest well developed, shorter than primary, with 5–9 broad teeth. Outer surface of palm striated proximally, granular distally, near upper margin of palm, naked; inner surface of palm with several tubercles. Fixed finger rounded, granular on outer surface. Dorsal surface of dactylus with 11–14 tubercles (Fig. 3 E), small proximally, becoming larger distally; tubercles distinct, subcircular, each tubercle with fine transverse lines, transverse ridge on tip; last 2 tubercles usually indistinct. Several low tubercles on proximal third of upper surface, proximal third of inner edge of dorsal surface with row of large tubercles. Fingers with tips chitinous
Walking legs robust, flattened, broad (Figs. 2 A, B, 3A); second, third pairs sub-equal, longer than others, about 1.5 times carapace width. Merus of third leg approximately twice as long as wide; upper margin of merus with acute subdistal spine. Carpus with 2 accessory carinae on outer surface. Propodi of legs 2–5, 2.7 times as long as wide, short stiff brush-like setae along dorsal margin, ventral margins with few long, stiff setae. Dactylus almost same length as propodus, slightly recurved, terminating in acute calcareous tip, dorsal, ventral margin with several long stiff setae.
Male abdomen relatively broad (Figs. 3 C, 4E). Telson semicircular, evenly rounded, slightly longer than somite 6; somite 6 almost 2.5 times as long as wide, lateral margins slightly convex. Somites 3–5 progressively more trapezoidal, lateral margins of somites 4, 5 straight, lateral margins of somite 3 slightly convex, somite 1, 2 very narrow longitudinally.
G1 slender (Fig. 4 A–D), apical process long, bent to form an angle of 45º, produced, corneous part long, slightly sinuous, tip rounded. Setae long, simple, originating at base of apical process. G2 very short.
Female with chelipeds smaller than in male, pectinated crests on palm replaced by 2 transverse rows of tubercles, dactylar tubercles indistinct.
Colour. Specimen from Phuket: carapace brownish orange, chelipeds brownish yellow to orange (Fig. 2 A). Specimen from Lombok Island: carapace brownish dark green with dark brown tuft of setae. Surface of palm of cheliped brownish red on upper part, lower part orange-red, fingers dark red (Fig. 2 B, C).
Remarks. Fabricius used the name Cancer quadratus twice for two different species, once in 1787 and again in 1798. Cancer quadratus Fabricius, 1787 (type locality Jamaica), is now known to be a species of Ocypode quadratus (see Manning & Holthuis 1981) and is a West African taxon. The name Cancer quadratus Fabricius, 1798 (type locality East India), however, was used for a sesarmine crab (now Sesarmidae), which was eventually transferred to the genus Sesarma (see H. Milne Edwards 1837). Latreille (1803), however, had apparently realised that the same name has been used twice for different species, and in a brief comment “Têt uni, avec les angles antérieurs formant une dent, et des plis derrière; main presque lisses. Ce crustacé est peutêtre un grapse” he proposed a new name, Ocypode plicatum. This is the species now generally referred to as Parasesarma plicatum. Almost all authors cite the author and year for Parasesarma plicatum as “ Latreille, 1806 ” (see Tesch 1917; Ng et al. 2008). The name was, however, first used as a valid name by Latreille (1803: 47) with a proper description and also clearly referring to the Cancer quadratus of Fabricius (1798).
Fabricius (1798) briefly described Cancer quadratus from an unspecified number of specimens from somewhere in East India. Four specimens of Cancer quadratus deposited at ZMUC have syntype status. Neil Bruce was kind enough to provide photographs of the dried types in the early 1990s which have since been rehydrated and examined by the second author. As Latreille (1803) merely provided a replacement name for the preoccupied name Cancer quadratus (i.e. Cancer plicatum), Fabricius' type specimens of Cancer quadratus are thus also the types of C. plicatum. Zimsen (1964) mentions five specimens and old photographs taken of the dried specimens in ZMUC in the 1960s show five specimens. However, the second author was only able to find and examine four of the subsequently rehydrated ZMUC specimens. Comparisons of the extant ZMUC specimens with the ZRC specimens from Tamil Nadu and Mumbai (= Bombay), India, as well as Phuket, Thailand show that all of them are conspecific. The best ZMUC male specimen (21.0 x 17.0 mm) is here selected as the lectotype (ZMUC 2658) (Fig. 1).
The most distinctive external feature of Parasesarma plicatum is that in addition to the two oblique rows of beige-coloured pectinated ridges on the antero-subdistal part of the manus, there are several beige-coloured granules posterior to the ridges (Figs. 2 A, B, 3E). This feature is visible even in the old material. The G1 of P. plicatum is also very distinctive (Fig. 4 A–D), the distal part being hook-shaped with a rounded tip.
The number of dactylar tubercles on the chela of P. plicatum is relatively constant, varying only from 11 to 14 (all granules counted, including the small proximal and very low distal ones) (Fig. 3 D, E). The number of these tubercles easily distinguishes P. plicatum from P. affine, which has only eight or nine dactylar granules (Fig. 6 E). These tubercles are also larger and more prominent in P. a f f i n e, with a prominent ridge at the tip. Furthermore, the G1 of P. plicatum (Fig. 4 A, B) is relatively more slender than that of P. affine (Fig. 7 A, B).
With regards to the affinities with P. exquisitum alluded to by Dai & Song (1986), we have compared P. plicatum with photographs of the holotype of P. exquisitum taken for us by N. K. Ng and T. Naruse (see comparative material). While P. exquisitum also has oblique rows of beige-coloured pectinated ridges on the antero-subdistal part of the manus, the number of tubercles on the dorsal surface of dactylus of chelipeds is much larger (17–19). They are clearly different species and not closely related.
Several specimens from Iraq are here identified as Parasesarma aff. plicatum. These specimens belong to the same species-group and share many characters with P. plicatum. However, a number of differences indicate that they belong to a different species, and in an independent study, Nardeloo & Schubart (in press) regard the taxon as new. As P. plicatum sensu stricto occurs in the eastern Indian Ocean, the records of this species by Richters (1880:157) from Mauritius, Lenz & Richters (1881: 425) and De Man (1889: 434) from Madagascar, Borradaile (1907: 64) from Seychelles, Stebbing (1910: 321) and Barnard (1950: 127.) from South Africa, Tirmizi & Ghani (1996: 151, fig. 58) and Tirmizi et al. (1986: 28, fig. 11 A) from Pakistan, as well as the record of Sesarma ungulata by A. Milne-Edwards (1868: 71) from Zanzibar, and Sesarma affinis by Krauss (1843: 45) from South Africa, should most probably also be referred to this new species.
Most authors use the spelling plicata for this species but as the gender of the genus Sesarma and Parasesarma is neuter, it should correctly be plicatum instead.
Geographical distribution. Bombay, Tamil Nadu (India), Phuket (Thailand), Lombok (Indonesia).
description: Published as part of Rahayu, Dwi Listyo & Ng, Peter K. L., 2010, Revision of the Parasesarma plicatum (Latreille, 1803) species-group (Crustacea: Decapoda: Brachyura: Sesarmidae), pp. 1-22 in Zootaxa 2327 on pages 2-8, DOI: 10.5281/zenodo.193082