Pseudosesarma crassimanum (De Man, 1887 )

Ng, Peter K. L. & Schubart, Christoph D., 2017, On the taxonomy of Pseudosesarma edwardsii (De Man, 1887) and P. crassimanum (De Man, 1887) (Crustacea: Decapoda: Brachyura: Sesarmidae), with description of a new species from Sri Lanka, Raffles Bulletin of Zoology 65, pp. 655-669 : 661-663

publication ID	https://doi.org/ 10.5281/zenodo.13256838
publication LSID	lsid:zoobank.org:pub:345579E6-E31B-4093-A731-813296EC1F77
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treatment provided by	Felipe
scientific name	Pseudosesarma crassimanum (De Man, 1887 )
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Pseudosesarma crassimanum (De Man, 1887) View in CoL

( Figs. 1D, E View Fig , 2C, D View Fig , 8–11 View Fig View Fig View Fig View Fig , 13 View Fig )

Sesarma edwardsii var. crassimana De Man, 1887: 649 View in CoL .

Sesarma edwardsi var. crassimana View in CoL – De Man, 1888: 188, pl. 13 figs. 5, 6; Zehntner, 1894: 180; Lanchester, 1900: 757.

Sesarma (Episesarma) edwardsi var. crassimana View in CoL – De Man, 1895: 174.

Sesarma (Sesarma) edwardsi crassimana View in CoL – Tesch, 1917: 148; Ingle & Fernando, 1963: fig. 2c, d.

Sesarma crassimana View in CoL – Tweedie, 1940: 92; Tweedie, 1950: 343, fig. 2b.

Sesarma (Sesarma) crassimanum – Serène, 1968: 105.

Pseudosesarma crassimanum View in CoL – Serène & Soh, 1970: 399, 406; Naiyanetr, 1998: 102; Naiyanetr, 2007: 115; Rademacher & Mengedoht, 2011: 29.

“ Pseudosesarma ” crassimanum View in CoL – Ng et al., 2008: 222.

Material examined. Others: Lectotype (here designated), male (16.3 × 14.6 mm) ( NHM 1886.52b), 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 View Materials ), 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 GoogleMaps ; 2 males (21.9 × 19.5 mm, 18.5 × 16.3 mm), 2 females (larger 18.0 × 15.9 mm) ( ZRC 2017.0169 View Materials ), Gulf of Thailand, coll. aquarium trade, April 2017 . SINGAPORE – 1 male, 2 females ( ZRC 1985.422 View Materials – 424 View Materials ), 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) ( NNM-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 View Materials ), Johor, Mawai, Sungei Ulu Sedili , coll. T.M. Leong, 30 August 2002 ; 4 males, 3 females ( ZRC 2010.1768 View Materials ), 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 1999.0990 View Materials ), Pulau Tioman, Sungei Keliling , coll. H.H. Tan, 25 June 1999 ; 1 male, 8 females (largest 20.2 × 17.0 mm) ( ZRC 2011.1012 View Materials ), 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 2016.276 View Materials ), small freshwater stream at beginning of mangroves, Pulau Tioman, Sungei margins subparallel ( Figs. 2C View Fig , 8 View Fig ); outer surface of chela gently convex, covered with small rounded granules, ventral margin of palm sinuous, denticulate, fingers relatively short compared to overall chela ( Figs. 1D View Fig , 9 View Fig , 13B, D, H, I View Fig ); suture between male thoracic sternites 3 and 4 distinct ( Fig. 10 View Fig ); male pleon broadly triangular ( Figs. 1E View Fig , 10 View Fig , 11A, N View Fig ); male sternopleonal cavity with press-button of pleonal locking mechanism on sternite 5; distal half of G1 gently swollen, much wider than proximal part, chitinous part forming beak-like structure ( Fig. 11B–F, H–L, O–R View Fig ) .

Colour. In life, smaller specimens have a dark brown carapace with somewhat more purplish-red chelae and yellowish fingers ( Fig. 13 View Fig ). Larger specimens have carapaces which are lighter brown, with the chelae dull red to yellow (see Rademacher & Mengedoht, 2011: 29).

Remarks. In naming Sesarma edwardsii, De Man (1887: 649) noted that “Eine Varietät dieser Art, crassimana genannt, unterscheidet sich hauptsächlich durch verhältnismässig kürzere Scheerenfinger.” This short sentence validates the name Sesarma edwardsii var. crassimana . De Man (1888: 188) states this variety as new, but it was first described in his 1887 paper (see above discussion for Pseudosesarma edwardsii and Ng et al., 2015: 217).

Keliling, coll. P.K.L. Ng, 19 August 2003; 1 male ( ZRC 1985.425 View Materials ), coll. D.S. Johnson , 31 July 1959; 5 males, 3 females ( ZRC 1999.0957 View Materials ), 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 View Materials ), 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 View Materials ), Tanjung Reolep, Sungai Berau , riverbank, Kalimantan, coll. R. Diesel , 2 September 1995. CAMBODIA – 1 male, 1 female ( ZRC 1965.7.29.52), Tonle Sap, Siam, coll. N. Annandale , 1918.

Diagnosis. Carapace transversely rectangular ( Figs. 2C View Fig , 8 View Fig ); frontal margin relatively wide, median concavity separating lobes distinct ( Fig. 2C View Fig ); epibranchial tooth distinct, separated from rest of margin by deep notch ( Figs. 2C View Fig , 8 View Fig ); posterolateral De Man (1887) did not specify how many specimens he had or where they were from, but later (De Man, 1888: 189) stated he had five males and three females from Zediwon, a location just east of Mergui. No types were designated, but he provided the measurements of the largest male, 19.25 × 17.25 mm. Ingle & Fernando (1963: 102, fig. 2c, d) noted that they had four syntype specimens in the NHM and they figured the distal part of the G1 of one of the males. The whereabouts of the remaining specimens is not known; they are not in Leiden or Amsterdam, or any of the German museums where his extant material is retained. The specimen figured by Ingle & Fernando (1963), a male measuring 16.3 × 14.6 mm (NHM 1886.52b) ( Fig. 8A View Fig ) is here designated as the lectotype of Sesarma edwardsii var. crassimana De Man, 1887 .

Originally described as Sesarma edwardsii var. crassimana , the species name was used as an adjective, on the incorrect assumption the gender of Sesarma is feminine. As the gender of Pseudosesarma is neuter, the name should be spelled as “ crassimanum ”.

The differences between P. edwardsii and P. crassimanum have been discussed under the former species.

Biology. This species is not uncommon at the banks of freshwater streams that are leading to the sea, although specimens have been found in back mangroves. They are typically hiding under small rocks and vegetation. They appear to be mainly nocturnal. On Pulau Tioman in Peninsular Malaysia, they have been observed to climb shrubs and small trees at night, apparently foraging on young shoots and buds. Distribution. Known only from Thailand, Cambodia, Peninsular Malaysia, Singapore and Borneo ( Tweedie, 1940, 1950; present data).