Pseudosesarma glabrum Ng, Rani & Nandan, 2017

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

Pseudosesarma glabrum Ng, Rani & Nandan, 2017

( Figs. 22F , 25E , 27F , 30D , 36H–L )

Pseudosesarma edwardsii – Shet et al., 2016: 8, 12, fig. 2 (not Sesarma edwardsii De Man, 1887 ).

Pseudosesarma glabrum Ng, Rani & Nandan, 2017: 265 , figs. 2–5; Trivedi et al., 2018: 73; Apreshgi & Abraham, 2018: 96; Pati et al., 2020: 139, figs. 2–4.

Material examined. Holotype: male (13.8 × 12.0 mm) ( CUSAT 2016-1 ), mangrove forest (mixed mangrove zone with human settlements), Aroor , Cochin estuary, part of Vembanad wetland, RAMSAR site , Kerala, India, coll. V. Rani et al., 16 January 2016. Paratypes: 1 male (12.2 × 10.3 mm) ( CUSAT 2016-2 ), same data as holotype ; 1 male (16.5 × 14.5 mm) ( CUSAT 2016-3 ), same location as holotype, coll. 3 March 2017. Others : INDIA – 2 males, 1 female ( ZRC 2019.0487 ), Thejaswini River, near Palayi Kadavu, Kasaragod district , Kerala, 12.261°N 75.165°E, coll. students, 10 October 2018 .

Diagnosis. Carapace slightly wider than long, width to length ratio 1.15–1.18; dorsal surface, including anterior part almost glabrous, without setae, with only short, barely visible scattered setae on posterolateral regions; frontal margin wide, median concavity separating lobes shallow; lateral margin with 1 distinct low epibranchial tooth, posterolateral margins subparallel; chela short, stout, fingers just shorter than palm, outer surface of palm with numerous small rounded granules, ventral margin of fixed finger and distal half of palm straight; suture between male thoracic sternites 3 and 4 distinct, straight; male pleon broadly triangular, somite 6 wide with distinctly convex lateral margins; male sternopleonal cavity with press-button of pleonal locking mechanism on anterior edge of sternite 5; G1 stout, distal part dilated forming bulbous structure, chitinous tip relatively broad, appearing bifurcated. In life, chela purple, not extending beyond base of fingers.

Colour. In life, the carapace is dark grey to brown with patches of lighter grey and brown; with the merus of the cheliped orange and the palm purple to dark orangish-brown and fingers white. The ambulatory legs are light brown with some parts orange ( Ng et al., 2017a: 267, fig. 5; Pati et al., 2020: fig. 2).

Remarks. Pseudosesarma glabrum was described and figured in detail by Ng et al. (2017a). It closely resembles P. crassimanum , but can easily be separated by the median cleft of the frontal margin being relatively more shallow ( Fig. 22F ), the anterior part of the dorsal surface of the carapace is almost glabrous except for a few very small scattered setae on the posterolateral regions ( Fig. 22F ), the ventral margin of the pollex and distal half of the palm of the adult chela is almost straight ( Fig. 27F ), the male pleon is relatively wider ( Fig. 30D ), and the G1 distal chitinous process is relatively shorter, wider, and appears bifurcated ( Fig. 36I–K ) (versus the median cleft of the frontal margin deeper, most of dorsal carapace surface covered with scattered but distinct stiff setae, the ventral margin of the pollex and distal half of the palm of the adult chela is distinctly concave, the male pleon is relatively narrower and the G1 distal chitinous process is beak-like, longer, and narrower in P. crassimanum ; Figs. 22D , 27D , 30C , 35 B–F, H–L, O–R).

Biology. Pseudosesarma glabrum is semi-terrestrial in habits, occurring in the intertidal mixed mangrove forests of Aroor in the Cochin estuary, Kerala, India. Sympatric sesarmids include Parasesarma plicatum ( Latreille, 1803) and Neosarmatium malabaricum ( Henderson, 1893) ( Ng et al., 2017a: 269) .

Distribution. The species was described from northern Kerala ( Ng et al., 2017a) but has since been found in other parts of Kerala state as well as in Karnataka and Maharashtra in western India ( Pati et al., 2020).

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. 36. A–G, Pseudosesarma anteactum, holotype male (16.7 × 14.7 mm) (ZRC 2016.0602), Sri Lanka; H–L, P. glabrum, holotype male (13.8 × 12.0 mm) (CUSAT 2016-1), Kerala, India. A, I, left G1 (ventral view); B, J, left G1 (dorsal view); C, D, distal part of left G1 (ventral view, slightly different angles); E, K, ventro-mesial view of distal part of left G1; F, distal part of left G1 (dorsal view); G, L, left G2; H, pleon. Scales: A, B, G = 1.0 mm; C–F, I–L = 0.5 mm; H = 2.0 mm. A–G, after Ng & Schubart (2017: fig. 17); H–L, after Ng et al. (2017a: fig. 4).

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).