Manarma moeschii ( De Man, 1892 )

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, Raffles Bulletin of Zoology 68, pp. 891-994 : 962-964

Manarma moeschii ( De Man, 1892)

( Figs. 24C , 26A , 29B , 33A, D, H , 41A–E , 44J , 58 )

Sesarma intermedia – De Man, 1888: 182. [not Grapsus (Pachysoma) intermedius De Haan, 1835 ]

Sesarma moeschii De Man, 1892: 331 , pl. 20 fig. 14; Tweedie, 1940: 92, fig. 3, pl. 24-1.

Sesarma intermedium – Alcock, 1900: 416. [not Grapsus (Pachysoma) intermedius De Haan, 1835]

Sesarma (Sesarma) moeschii – Tesch, 1917: 177.

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

Pseudosesarma moeschi – Naiyanetr, 1998: 102; Naiyanetr, 2007: 116; Rademacher & Mengedoht, 2011: 28; Ribero, 2020: 3, 6.

“ Pseudosesarma ” moeschi – Ng et al., 2008a: 220.

Pseudosesarma crassimanum – Li et al., 2020: 3, 29–30. [not Sesarma edwardsii var. crassimana De Man, 1887: 649 ]

Material examined. BRUNEI – 1 male (13.6 × 12.2 mm) ( ZRC 2016.0405 ), Sungei Belayang , coll. G. Polgar & L. Ribero, 15 October 2013 . THAILAND – 8 males (largest 20.2 × 18.0 mm, smallest 15.8 × 14.5 mm) , 2 females (17.5 × 15.4 mm, 15.9 × 14.3 mm) ( ZRC 2000.1926 ), probably central Thailand, Thailand , purchased from Bangkok market, coll. P.K.L. Ng & C.D. Schubart, 20 February 2000 ; 5 males (largest 19.7 × 17.1 mm), 2 females (larger 19.3 × 17.3 mm) ( ZRC 2017.0170 ), Gulf of Thailand , coll. aquarium trade, April 2017 .

Diagnosis. Dorsal surface of carapace relatively more swollen, regions prominent; fingers of cheliped relatively longer in adult males; male pleonal somite 6 relatively shorter, telson more triangular; distal chitinous part of G1 relatively straighter, more tapering. In life, carapace dark grey to almost black with a gentle marbling.

Colour. The carapace is dirty brown with scattered blotches and spots of light brown and grey, giving it a “marbled” appearance. The chelae are bright red ( Rademacher & Mengedoht, 2011: 28).

Remarks. De Man (1892: 331) described Sesarma moeschii on the basis of two males (15.75 × 13.25 mm, 15.25 × 13.5 mm) from the Batak territories in Deli, northern Sumatra. The depository for this material is uncertain. Fortunately, the specimens on hand from Peninsular Malaysia and Thailand agree very well with the type description and excellent figures in De Man (1892: 331–333, pl. 20 fig. 14) and we have little doubt they are conspecific.

Manarma moeschii can be distinguished from M. johorense by the dorsal surface of the carapace being more swollen ( Figs. 24C , 26A ) (flatter and the regions relatively less prominent in M. johorense due to the shallow grooves, Figs. 24D , 26B ); the fingers of the cheliped being relatively longer in adult males ( Fig. 29B ) (relatively shorter in M. johorense , Fig. 29C ); male pleonal somite 6 being relatively shorter with the telson more triangular ( Fig. 41A ) (relatively longer with the telson more rounded in M. johorense , Fig. 41F ); and the distal chitinous part of the G1 being relatively straighter and more tapering ( Fig. 41B–E ) (distally gently curved distally in M. johorense , Fig. 41G–J ). Their live colours are also different, with the carapace of M. moeschii dark grey to almost black with a gentle marbling ( Fig. 58C, D ) whilst that of M. johorense is a uniform dark brown ( Tweedie, 1940: 105). In addition, the chela is red in M. moeschii ( Fig. 58B, E, G, H ) but yellow in M. johorensis (cf. Tweedie, 1940: 105).

Tweedie (1940: 92) commented that the male pleon of his specimen from Peninsular Malaysia ( Tweedie, 1940: fig. 3a) has a relatively more slender pleonal somite 6 compared to that from the Bay of Gorontalo in Sulawesi ( Tweedie, 1940: fig. 3b). This was the same specimen reported by Tesch (1917). Tweedie, however, noted that the differences do not appear to be substantial.

Biology. Tweedie (1940: 92) commented that he had “ one adult male from among nipah palms beside the river Sedili, Johore”. Ribero et al. (2020: 6) found that the species was mainly associated with dense Nipah forests in Brunei. The species is, however, widely collected for the aquarium trade (see Rademacher & Mengedoht, 2011). One source is from the back mangroves of Chonburi in central Thailand in the Gulf of Thailand; and we have specimens from this area obtained by local collectors.

Distribution. Sumatra, Peninsular Malaysia, Thailand, and Sulawesi ( De Man, 1892; Tesch, 1917; Tweedie, 1940; Naiyanetr, 1998, 2007).

Figures

Fig. 24. Overall habitus. A, Miersarma granosimanum, lectotype male (16.9 × 14.8 mm) (NHM 1880.6), Borneo; B, Miersarma granosimanum, male (22.5 × 19.2 mm) (ZRC 1965.7.29.164), Sedili River, Johor, Malaysia; C, Manarma moeschii, male (18.2 × 16.3 mm) (ZRC 2000.1926), Thailand; D, Manarma johorense, male (14.6 × 12.6 mm) (ZRC 1971.9.24.14), Seletar River, Singapore; E, Bresedium laevimanum, lectotype male (20.0 × 17.6 mm) (MNHG), Borneo; F, Bresedium laevimanum, male (26.3 × 23.7 mm) (NHM) (lectotype of Sesarma sediliensis), Johor, Malaysia; G, Bresedium laevimanum, male (18.1 × 16.4 mm) (ZRC 1972.3.7.25), Sarawak, Borneo; H, Bresedium laevimanum, male (21.2 × 18.2 mm) (ZRC 1965.7.29.121), Johor, Malaysia.

Fig. 26. Frontal view of cephalothorax. A, Manarma moeschii, male (18.2 × 16.3 mm) (ZRC 2000.1926), Thailand; B, Manarma johorense, male (14.6 × 12.6 mm) (ZRC 1971.9.24.14), Seletar River, Singapore; C, Bresedium laevimanum, lectotype male (20.0 × 17.6 mm) (MNHG), Borneo; D, Bresedium laevimanum, male (26.3 × 23.7 mm) (NHM) (lectotype of Sesarma sediliensis), Johor, Malaysia.

Fig. 29. Outer view of chela. A, Miersarma granosimanum, lectotype male (16.9 × 14.8 mm) (NHM 1880.6), Borneo; B, Manarma moeschii, male (18.2 × 16.3 mm) (ZRC 2000.1926), Thailand; C, Manarma johorense, male (14.6 × 12.6 mm) (ZRC 1971.9.24.14), Seletar River, Singapore; D, Bresedium laevimanum, lectotype male (20.0 × 17.6 mm) (MNHG), Borneo; E, Bresedium laevimanum, male (26.3 × 23.7 mm) (NHM) (lectotype of Sesarma sediliensis), Johor, Malaysia; F, Bresedium laevimanum, male (18.1 × 16.4 mm) (ZRC 1972.3.7.25), Sarawak.

Fig. 33. A–E, male anterior thoracic sternum and pleon; F–H, left ambulatory leg. A, D, H, Manarma moeschii, male (18.2 × 16.3 mm) (ZRC 2000.1926), Thailand; B, E, M. johorense, male (14.6 × 12.6 mm) (ZRC 1971.9.24.14), Seletar River, Singapore; C, F, Orisarma intermedium, male (34.7 × 31.6 mm) (ZRC 2001.0034), Pingtung, Taiwan; G, O. patshuni (, male (14.2 × 13.0 mm) (ZRC 1998.345), Hong Kong.

Fig. 41. A–E, Manarma moeschii, male (20.2 × 18.0 mm) (ZRC 2000.1926), Thailand; F–J, M. johorense, male (14.6 × 12.6 mm) (ZRC 1971.9.24.14), Seletar River, Singapore. A, F, male pleon; B, G, left G1 (ventral view, denuded); C, H, left G1 (dorsal view, denuded); D, I, left distal part of G1 (ventral view, denuded); E, J, left distal part of G1 (dorsal view, denuded). Scales: A = 5.0 mm; B, C, G, H = 1.0 mm; F = 2.0 mm; D, E, I, J = 0.5 mm.

Fig. 44. Vulva. A, Pseudosesarma edwardsii, female (16.5 × 15.3 mm) (ZRC 2016.0608), Malaysia; B, Pseudosesarma crassimanum, female (15.9 × 13.8 mm) (ZRC 2000.1768), Malaysia; C, Pseudosesarma crassimanum, female (18.0 × 15.7 mm) (ZRC 2017.1045), Thailand; D, Pseudosesarma anteactum, paratype female (17.5 × 15.4 mm) (ZRC 2016.0603), Sri Lanka; E, Pseudosesarma brehieri, paratype female (14.9 × 13.4 mm) (ZRC 2016.0594), Myanmar; F, Pseudosesarma boulengeri, female (24.2 × 20.0 mm) (ZRC 2014.0335), Iran; G, Contusarma bocourti, female (21.1 × 19.0 mm) (ZRC 2019.1114), Thailand; H, Contusarma cheirogonum, female (26.6 × 23.0 mm) (ZRC 1964.9.28.127), Sarawak; I, Miersarma granosimanum, female (20.1 × 16.4 mm) (ZRC 1965.7.29.166), Malaysia; J, Manarma moeschii, female (19.3 × 17.3 mm) (ZRC 2017.0170), Thailand.

Fig. 58. Colour in life. Manarma moeschii. A, B, male, Thailand, specimen not preserved [photograph: Oliver Mengedoht]; C–H, male (19.7 × 17.1 mm) (ZRC 2017.0170), Thailand [photograph: Paul Ng].