Pseudosesarma crassimanum
Creators: name: Schubart, Christoph D.
name: Ng, Peter K. L.
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Sesarmidae
Pseudosesarma
Pseudosesarma crassimanum

description: Pseudosesarma crassimanum (De Man, 1887)
(Figs. 22D, 25C, 27D, 30C, 32 B, 35, 44 B, C, 56 F, G)
Sesarma edwardsii var. crassimana De Man, 1887: 649.
Sesarma edwardsi var. crassimana – De Man, 1888: 188, pl. 13 figs. 5, 6; Zehntner, 1894: 180; Lanchester, 1900: 757.
Sesarma (Episesarma) edwardsi var. crassimana – De Man, 1895: 174.
Sesarma (Sesarma) edwardsi crassimana – Tesch, 1917: 148.
Sesarma crassimana – Tweedie, 1940: 92; Tweedie, 1950: 343, fig. 2b.
Sesarma (Sesarma) crassimanum – Serène, 1968: 105.
Pseudosesarma crassimanum – Serène & Soh, 1970: 399, 406; Tan & Ng, 1994: 82; Naiyanetr, 1998: 102; Cuesta et al., 2006: 160, fig. 9A–E; Naiyanetr, 2007: 115; Rademacher & Mengedoht, 2011: 29; Ng & Schubart, 2017: 661, figs. 1D, E, 2C, D, 8–11, 13.
“ Pseudosesarma ” crassimanum – Ng et al., 2008a: 222.
Material examined. Lectotype: male (16.3 × 14.6 mm) (NHM 1886.52 b), mangrove swamps at Zediwon, Mergui Archipelago, Myanmar (= Burma), coll. J. Anderson, 1886. Paralectotypes: 1 male (18.8 × 16.7 mm), 2 females (16.6 × 14.3 mm, 12.5 × 11.0 mm) (NHM 1886.52 c), same data as lectotype. THAILAND – 1 male (15.9 × 14.3 mm) (ZRC 2008.0442), Ranong Province, King Amphoe Suk Sam Lan, Ton Roi waterfall, 9°27′29.2″N 98°30′31″E, Thailand, coll. D.C.J. Yeo et al., 12 August 1997; 2 males (21.9 × 19.5 mm, 18.5 × 16.3 mm), 2 females (larger 18.0 × 15.9 mm) (ZRC 2017.0169), Gulf of Thailand, coll. aquarium trade, April 2017. SINGAPORE – 1 male, 2 females (ZRC 1985.422 – 424), Sungei Seletar, coll. C.L. Soh, 23 September 1959; 1 male (17.5 × 15.0 mm) (ZRC 1967.7.21.4), Sungei Seletar, coll. C.L. Soh, 31 December 1966; 1 male (15.9 × 14.5 mm) (RMNH-D23313), probably from Singapore, don. R. Serène; 1 female (ZRC 1967.7.10), Sungei Seletar, coll. C.L. Soh, 6 May 1966; 2 males (ZRC 1967.7.10.40), Sungei Seletar, coll. C.L. Soh, 18 July 1966; 1 male (ZRC number), Simpang River, Mak Wai, coll. C.L. Soh, 18 February 1966; 2 females (ZRC 1973.11.2.493–494), Sungei Seletar, 29 March 1966; 1 male (ZRC 1967.7.10.39), coll. C.L. Soh; 1 male (ZRC 1971.9.22.10), no other data, coll. C.L. Soh; 1 male, 3 females (ZRC), no other data. PENINSULAR MALAYSIA – 1 male (ZRC 2003.0054), Johor, Mawai, Sungei Ulu Sedili, coll. T.M. Leong, 30 August 2002; 4 males, 3 females (ZRC 2010.1768), Johor, Sungei Benut Cintom, coll. C.D. Schubart et al., 30 September 1999; 2 males, 1 female (ZRC 1964.9.25.210–212), Sedili River, Johor, coll. M.W.F. Tweedie, 1938; 1 male (ZRC 1999.990), Pulau Tioman, Sungei Keliling, coll. H.H. Tan, 25 June 1999; 1 male, 8 females (largest 20.2 × 17.0 mm) (ZRC 2011.1012), Pulau Tioman, Sungei Keliling, coll. P.K.L. Ng et al., 27–28 January 1996; 1 male (12.6 × 10.5 mm) (ZRC), 1 female (ZRC 2016.0276), small freshwater stream at beginning of mangroves, Pulau Tioman, Sungei Keliling, coll. P.K.L. Ng, 19 August 2003; 1 male (ZRC 1985.425), coll. D.S. Johnson, 31 July 1959; 5 males, 3 females (ZRC 1999.957), Pulau Tioman, Sungei Keliling, coll. H.H. Tan et al., 25 June 1998. SARAWAK – 1 male (14.0 × 11.9 mm) (MNHG), coll. Bedot & Pichet, 1800s; 14 males, 10 females (ZRC 1964.9.25.368–379), Kuching, coll. M.W.F. Tweedie, 1950; 1 male (18.9 × 16.7 mm) (ZRC 1999.851), stream 3 km before turn off to Cape Pelandok and Kampung Pandan, after Landa town, drains from Sungei Gading, coll. H.H. Tan, 2 September 1996; 3 males (ZRC 1964.9.28.14–16), Stambak, Saribas, coll. L.K. Charles, 1950. INDONESIA – 2 males (17.2 × 15.0 mm, 14.3 × 12.3 mm) (ZRC 1999.503), Tanjung Reolep, Sungai Berau, riverbank, Kalimantan, coll. R. Diesel, 2 September 1995. THAILAND – 2 males, 1 female (ZRC 2017.1045), from aquarium trade, coll. P.K.L. Ng, 2017. CAMBODIA – 1 male, 1 female (ZRC 1965.7.29.52), Tonle Sap, Siam, coll. N. Annandale, 1918.
Diagnosis. Carapace transversely rectangular; frontal margin relatively wider, median concavity separating lobes more distinct; epibranchial tooth distinct, separated from rest of margin by deep notch; posterolateral margins subparallel; outer surface of chela gently convex, covered with small rounded granules, ventral margin of palm sinuous unarmed; suture between male thoracic sternites 3 and 4 distinct; male pleon broadly triangular; male sternopleonal cavity with press-button of pleonal locking mechanism on sternite 5; distal part of G1 gently swollen with chitinous part forming beak-like structure. In life, chela purplish red to yellow, pigmentation reaching to base of yellowish-white fingers.
Colour. In life, smaller specimens have a darker brown carapace with purple chelae and yellowish fingers (Fig. 56F, G). Larger specimens have carapaces which are lighter brown, with the chelae purplish-red to yellow (Rademacher & Mengedoht, 2011: 29) (see also Ng & Schubart, 2017).
Remarks. The differences between P. edwardsii and P. crassimanum have been discussed at length by Ng & Schubart (2017).
Li et al. (2020: 3, 29, 30) list “ Pseudosesarma crassimanum ” for the molecular tree they used in a study of Sesarmops impressus (H. Milne Edwards, 1837). Its genetic data, however, aligns with what is here regarded as Manarma moeschii (De Man, 1892) (see later). The material that was used for the study by Li et al. (2020) originated from the aquarium trade and was misidentified, they are actually M. moeschii (H.-T. Shih, pers. comm.).
Biology. This species seems to prefer to hide under small rocks and vegetation along the banks of coastal freshwater streams leading to the sea, but they have also been found in the rearward mangrove zones. They appear to be mainly nocturnal. On Pulau Tioman in Malaysia, they have been observed to climb up shrubs and small trees at night, apparently foraging for young shoots and buds. The larvae have been reported on by Cuesta et al. (2006).
Distribution. Known only from Thailand, Peninsular Malaysia, Singapore, and Borneo (Tweedie, 1940, 1950).
description: Published as part of Schubart, Christoph D. & Ng, Peter K. L., 2020, Revision of the intertidal and semiterrestrial crab genera Chiromantes Gistel, 1848, and Pseudosesarma Serène & Soh, 1970 (Crustacea: Brachyura: Sesarmidae), using morphology and molecular phylogenetics, with the establishment of nine new genera and two new species, pp. 891-994 in Raffles Bulletin of Zoology 68 on pages 947-948, DOI: 10.26107/RBZ-2020-0097, http://zenodo.org/record/5351295