Pseudosesarma brehieri Ng, 2018

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 : 950-952

Pseudosesarma brehieri Ng, 2018

( Figs. 22G , 25F , 27G , 30G , 37A–I , 44 E)

Pseudosesarma brehieri Ng, 2018: 191 , figs. 4–6, 7D–I; Trivedi et al., 2020: 4, fig. 3.

Material examined. Holotype: male (17.4 × 15.7 mm) ( ZRC 2016.0593 ), Nathack Gu ( Two Level Cave ), near Saddan Sin Gu, Mawlamyine (Moulmein), Mon State, 16°31′33.5″N 097°42′48.8″E, Myanmar, coll. F. Bréhier et al., 26 November 2016. Paratype: 1 female (14.9 × 13.4 mm) ( ZRC 2016.0594 ), same data as holotype. Others : INDIA – 5 males (11.9 × 10.4 mm, 12.4 × 10.9 mm, 13.6 × 11.7 mm, 14.5 × 13.0 mm, 15.0 × 13.6 mm) ( ZRC 2013.0209 ), river bank, Bhagirath, Nabadiwip, Nadia, West Bengal, coll. Z. Jaafar et al., 26 December 2004 .

Diagnosis. Carapace quadrate, slightly wider than long, width to length ratio 1.1; frontal margin wide, median concavity separating lobes relatively shallow; external orbital tooth short, not reaching to level of front, lateral margin with 2 epibranchial teeth; posterolateral margins subparallel; chela short, stout, fingers shorter than palm, outer surface of chela covered with numerous granules, ventral margin of palm almost straight or gently convex; suture between male thoracic sternites 3 and 4 distinct; male pleon triangular, somite 6 wide; male sternopleonal cavity with press-button of pleonal locking mechanism on sternite 5; G1 stout, distal part prominently dilated forming bulbous structure, chitinous tip short, broad, truncate, fan-like.

Colour. Not known.

Remarks. The species was described and figured in detail by Ng (2018). Pseudosesarma brehieri most closely resembles P. crassimanum but can easily be separated by the ventral margin of its adult male chela being almost straight ( Fig. 27G ) and the distal half of the G1 being proportionately more dilated with the chitinous distal part very wide and fan-like ( Fig. 37B–D, F–I ) (versus ventral margin of adult male chela gently concave, and the G1 distal part less dilated with the chitinous distal part narrow and beak-like in P. crassimanum ; Figs. 27D , 35 B–F, H–L, O–R).

Biology. Ng (2018: 193, 195) observed that the type specimens of P. brehieri were found in a small upper chamber of a cave at the foot of the hill not far from Saddan Sin Gu in southern Myanmar. The water in the cave was completely fresh. The site is not far from the sea and the species is clearly not an obligate cave species with well developed eyes and normal colouration. Trivedi et al. (2020: 4) recorded the species from India, noting that the material was “collected from [the] muddy shore of Hooghly River at Barrackpore city of West Bengal state which is considered as upper reaches of Hooghly-Matla estuary, where tidal effects usually occur with a low salinity (0.5 to 4 ppm) of interstitial waters”. The present specimens from India were collected from the side of a riverbank in an estuarine habitat in West Bengal, India.

Distribution. The species was described from Myanmar and we now also have specimens from Bengal in eastern India (ZRC 2013.0209).

Figures

Fig. 22. Overall habitus, Pseudosesarma species. A, P. edwardsii, lectotype male (17.5 × 16.1 mm) (RMNH-D17a), Mergui Archipelago; B, P. edwardsii, male (13.4 × 11.9 mm) (ZRC 1965.8.2.81), Pulau Pawai, Singapore; C, P. edwardsii, male (12.9 × 11.8 mm) (ZRC 1971.9.24.9), Singapore; D, P. crassimanum, male (15.9 × 14.5 mm) (RMNH-D23313), Singapore; E, P. anteactum, holotype male (16.7 × 14.7 mm) (ZRC 2016.0602), Sri Lanka; F, P. glabrum, holotype male (13.8 × 12.0 mm) (CUSAT 2016-1), Kerala, India; G, P. brehieri, holotype male (17.4 × 15.7 mm) (ZRC 2016.0593), Myanmar; H, P. boulengeri, lectotype male (26.9 × 23.5 mm) (NHM 1919.11.14.1), Basra, Iraq.

Fig. 25. Frontal view of cephalothorax of Pseudosesarma. A, P. edwardsii, lectotype male (17.5 × 16.1 mm) (RMNH-D17a), Mergui Archipelago; B, P. edwardsii, male (13.4 × 11.9 mm) (ZRC 1965.8.2.81), Pulau Pawai, Singapore; C, P. crassimanum, male (15.9 × 14.5 mm) (RMNH-D23313), Singapore; D, P. anteactum, holotype male (16.7 × 14.7 mm) (ZRC 2016.0602), Sri Lanka; E, P. glabrum, holotype male (13.8 × 12.0 mm) (CUSAT 2016-1), Kerala, India; F, P. brehieri, holotype male (17.4 × 15.7 mm) (ZRC 2016.0593), Myanmar; G, P. boulengeri, lectotype male (26.9 × 23.5 mm) (NHM 1919.11.14.1), Basra, Iraq; H, Contusarma bocourti, male (25.3 × 23.3 mm) (ZRC 2000.0952), Bangkok, Thailand; I, Contusarma cheirogonum, neotype male (24.5 × 21.5 mm) (ZRC 1995.225), Bako National Park, Sarawak; J, Miersarma granosimanum, lectotype male (16.9 × 14.8 mm) (NHM 1880.6), Borneo.

Fig. 27. Outer view of chela of Pseudosesarma. A, P. edwardsii, lectotype male (17.5 × 16.1 mm) (RMNH-D17a), Mergui Archipelago; B, P. edwardsii, male (13.4 × 11.9 mm) (ZRC 1965.8.2.81), Pulau Pawai, Singapore; C, P. edwardsii, male (19.4 × 17.3 mm) (ZRC 1971.9.24.8), Singapore; D, P. crassimanum, male (15.9 × 14.5 mm) (RMNH-D23313), Singapore; E, P. anteactum, holotype male (16.7 × 14.7 mm) (ZRC 2016.0602), Sri Lanka; F, P. glabrum, holotype male (13.8 × 12.0 mm) (CUSAT 2016-1), Kerala, India; G, P. brehieri, holotype male (17.4 × 15.7 mm) (ZRC 2016.0593), Myanmar; H, P. boulengeri, lectotype male (26.9 × 23.5 mm) (NHM 1919.11.14.1), Basra, Iraq.

Fig. 30. Male anterior thoracic sternum and pleon of Pseudosesarma. A, P edwardsii, lectotype male (17.5 × 16.1 mm) (RMNH-D17a), Mergui Archipelago; B, P. edwardsii, male (13.4 × 11.9 mm) (ZRC 1965.8.2.81), Pulau Pawai, Singapore; C, P. crassimanum, male (15.9 × 14.5 mm) (RMNH-D23313), Singapore; D, P. glabrum, holotype male (13.8 × 12.0 mm) (CUSAT 2016-1), Kerala, India; E, P. anteactum, holotype male (16.7 × 14.7 mm) (ZRC 2016.0602), Sri Lanka; F, P. anteactum, paratype male (21.2 × 19.7 mm) (ZRC 2016.0603), Sri Lanka; G, P. brehieri, holotype male (17.4 × 15.7 mm) (ZRC 2016.0593), Myanmar; H, P. boulengeri, lectotype male (26.9 × 23.5 mm) (NHM 1919.11.14.1), Basra, Iraq.

Fig. 37. A–G, Pseudosesarma brehieri, paratype female (14.9 × 13.4 mm) (ZRC 2016.0594), Myanmar; F, G, P. brehieri, male (15.0 × 13.6 mm) (ZRC 2013.0209), West Bengal, India; H, I, P. brehieri, male (14.5 × 13.0 mm) (ZRC 2013.0209), West Bengal, India; J–O, P. boulengeri, lectotype male (26.9 × 23.5 mm) (NHM 1919.11.14.1), Basra, Iraq. A, K, male pleon; B, F, L, left G1 (ventral view, denuded); D, G, M, left G1 (dorsal view, denuded); E, left G2; H, O, left distal part of G1 (dorsal view, denuded); I, N, left distal part of G1 (ventral view, denuded); J, anterior thoracic sternites 1–4. Scales: A = 4.0 mm; B–E, N, O = 1.0 mm; F–I = 0.5 mm; J, K = 5.0 mm; L, M = 2.0 mm. A–E, after Ng (2018: fig. 7E–I).

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. 35. A–E, Pseudosesarma crassimanum. A–G, lectotype male (16.3 × 14.6 mm) (NHM 1886.52b), Myanmar; H–M, male (15.9 × 14.3 mm) (ZRC 2008.0442), Ranong; N–R, male (15.9 × 14.5 mm) (RMNH-D23313), Singapore. A, N, pleon; B–F, right G1; G, right G2; H–L, O–R, left G1; M, left G2. Scales: A = 2.0 mm; B, G, H, I, M, O, P = 1.0 mm; N = 5.0 mm; C–F, J–L, Q, R = 0.5 mm. After Ng & Schubart (2017: fig. 11).