Trapezarma angolense ( Brito Capello, 1864 )

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 : 936

Trapezarma angolense ( Brito Capello, 1864)

( Figs. 13G , 14G , 16 , 18E , 21A–G , 43I )

Sesarma angolensis Brito Capello, 1864: 4 , fig. 2; De Man, 1883: 161; Büttikofer, 1890: 487; Johnston, 1906: 861; Longhurst, 1958: 88; Gauld, 1960: 71.

Sesarma (Holometopus) angolensis – De Man, 1900: 59, pl. 2 fig. 11; Tesch, 1917: 130; Dartevelle, 1950: 48; Monod, 1956: 445, fig. 605; Rossignol, 1962: 120.

Sesarma (Holometopus) angolense – Rathbun, 1921: 451, pls. 43, 45 fig. 1; Dartevelle, 1950: 50; Capart, 1951: 191, fig. 76; Rossignol, 1957: 92, 122 [key]; Jordan, 1957: 198; Humes, 1957: 186, 187, 189.

Sesarma (Parasesarma) angolensis – Rathbun, 1900: 280.

Sesarma (Chiromantes) angolense – Manning & Holthuis, 1981: 243.

“ Chiromantes ” angolense – Ng et al., 2008a: 220.

Material examined. ANGOLA – Neotype (here designated): male (39.3 × 32.7 mm) ( SMF-ZMG 635 a), Benguella, river mouth of Catumbella near Benguella, coll. M.P. Kammerman; 1 ovigerous female (39.6 × 33.8 mm) ( SMF-ZMG 635 b), same data as neotype; 1 male, 2 females ( RMNH D 1200 ), Lobito, coll. P. Kamerman, 1899. CAMEROON – 1 juvenile male ( SMF 25982), West Nimbe (Limbe or Victoria), Mile 6, north of Nimbe, between pieces of basalt, coll. C.H. Otto, 7 January 1984; 2 males (35.2 × 28.6 mm, 21.2 × 16.3 mm), 1 female (18.2 × 14.3 mm) ( ZRC 2015.0297 ), Lokoundjié mangrove, coll. P.A. Mvogo-Ndongo, 21 June 2015. LIBERIA – 2 females ( RMNH D 1937 ), coll. J. Demery, 1890–1897.

Diagnosis. Carapace distinctly trapezoidal; frontal margin entire; lateral margins of carapace strongly converging to posterior carapace margin; cheliped merus with inner margin serrated but not expanded; adult male chela stout, outer surface gently convex, in large males, pollex may be expanded, shear-like, more flattened; male thoracic sternites 2–4 narrow in adults, suture between sternites 3 and 4 distinct; male sternopleonal cavity reaching three-quarters length of sternite 4 to just before anterior margin of sternite 2; male thoracic sternite 5 smooth, without depression on anterior part; male pleon elongate, narrow, telson linguiform; G1 relatively stout, chitinous part short.

Colour. The colour was described in detail by Rossignol (1957: 92): carapace blue-green with a yellow margin; ambulatory legs of the same colour as the carapace with a red dot to the joints, end dactylus yellow-orange dactyls; pincers colour of yellow leather with a red spot at the joint of the chela and fingers; eyes with light blue or gray-blue peduncle; cornea brown with a red dot; pleon dirty yellow with a blue median transverse line spanning somite 1; thoracic articles yellow and blue (translated from the French).

Remarks. In naming this species, Brito Capello did not indicate how many specimens he had. All he stated was that the species was from “mares de Angola ” ( Brito Capello, 1864: 4). Unfortunately, all of Brito Capello’s material in the Lisbon Museum were lost in a fire in 1978, and the types of this species are no longer extant. While the identity of this species is currently not in doubt, because it is here designated as the type species for Trapezarma , new genus, it is important to ensure a stable taxonomy. As such, we designate a large male specimen in the Senckenberg Museum (SMF-ZMG 635a) as the neotype of Sesarma angolensis Brito Capello, 1864 .

There is considerable variation in the form of the male chela. The largest male from Angola (the neotype male) has a more typical chela in which the pollex is relatively slender and the dactylus gently curved ( Fig. 16A ). In the smaller but clearly adult male from Cameroon, the pollex is strongly expanded, very broad, the outer surface more flattened, and the dactylus is strongly curved ( Fig. 16C, D ). The specimen figured by Brito Capello (1864: fig. 2c) shows a chela which is more intermediate in form. Other than this, the specimens from Cameroon and Angola are very similar and we have no reason to suspect they are different species. The characteristic male chela ( Fig. 16C, D ) noted above may be a feature of dominant males.

Biology. The best account of the biology of this species is given in Rathbun (1921: 451–452), who observes that it prefers the more freshwater sections of the river.

Distribution. Sierra Leone to Angola ( Monod, 1956; Manning & Holthuis, 1981).

Figures

Fig. 13. Overall habitus. A, Danarma obtusifrons, male (17.7 × 13.2 mm) (UF-FLMNH 14837), Oahu, Hawaii; B, Danarma silus, holotype male (16.3 × 12.8 mm) (ZRC 2012.0787), Guam; C, Danarma eurymerus, holotype male (18.7 × 14.8 mm) (NMNS-7028-002), Lanyu Island, Taiwan; D, Danarma garfunkel, holotype male (17.0 × 13.0 mm) (QM), Greta Beach, Christmas Island; E, Cristarma eulimene, male (22.2 × 17.2 mm) (ZRC 1968.1.22.2), Inhaca Island, Mozambique; F, Cristarma ortmanni, male (20.0 × 15.5 mm) (ZRC 1968.1.22.1), Inhaca Island, Mozambique; G, Trapezarma angolense, neotype male (39.3 × 32.7 mm) (SMF-ZMG 635), Benguella, Angola; H, Platychirarma buettikoferi, paralectotype male (10.0 × 8.7 mm) (SMF-ZMG 636), Fisherman Lake, Liberia; I, Platychirarma buettikoferi, lectotype male (14.1 × 11.6 mm) (RMNH D 148), Liberia; J, Platychirarma buettikoferi, male (12.6 × 10.4 mm) (ZRC 2015.0298), Cameroon.

Fig. 14. Frontal view of cephalothorax. A, Danarma obtusifrons, male (17.7 × 13.2 mm) (UF-FLMNH 14837), Hawaii; B, Danarma garfunkel, holotype male (17.0 × 13.0 mm) (QM, ex ZRC 2009.0822), Christmas Island; C, D, Danarma eurymerus, holotype male (18.7 × 14.8 mm) (NMNS-7028-002), Lanyu Island, Taiwan; E, Cristarma eulimene, male (22.2 × 17.2 mm) (ZRC 1968.1.22.2), Inhaca Island, Mozambique; F, Cristarma ortmanni, male (20.0 × 15.5 mm) (ZRC 1968.1.22.1), Inhaca Island, Mozambique; G, Trapezarma angolense, neotype male (39.3 × 32.7 mm) (SMF-ZMG 635), Benguella, Angola; H, Platychirarma buettikoferi, paralectotype male (10.0 × 8.7 mm) (SMF-ZMG 636), Fisherman Lake, Liberia.

Fig. 16. Chela of species of Trapezarma angolense. A, B, neotype male (39.3 × 32.7 mm) (SMF-ZMG 635), Benguella, Angola; C–F, male (35.2 × 28.6 mm) (ZRC 2015.0297), Cameroon. A, C, outer view; D, inner view; B, E, F, dorso-lateral view.

Fig. 18. Male anterior thoracic sternum and pleon. A, Danarma obtusifrons, male (19.7 × 14.7 mm) (ZRC 2002.0220), Oahu, Hawaii; B, Danarma eurymerus, holotype male (18.7 × 14.8 mm) (NMNS-7028-002), Lanyu Island, Taiwan; C, Cristarma eulimene, male (22.2 × 17.2 mm) (ZRC 1968.1.22.2), Inhaca Island, Mozambique; D, Cristarma ortmanni, male (20.0 × 15.5 mm) (ZRC 1968.1.22.1), Inhaca Island, Mozambique; E, Trapezarma angolense, neotype male (39.3 × 32.7 mm) (SMF-ZMG 635), Benguella, Angola; F, Platychirarma buettikoferi, paralectotype male (10.0 × 8.7 mm) (SMF-ZMG 636), Fisherman Lake, Liberia.

Fig. 21. A–G, Trapezarma angolense, neotype male (39.3 × 32.7 mm) (SMF-ZMG 635), Benguella, Angola; H–L, Platychirarma buettikoferi, 1 male (10.7 × 8.8 mm) (SMF 25980), West Nimbe Cameroon. A, H, male pleon; B, I, left G1 (ventral view, denuded); C, left G1 (dorso-lateral view) (denuded); D, J, left G1 (dorsal view, denuded); E, K, left distal part of G1 (ventral view, denuded); G, L, left distal part of G1 (dorsal view, denuded); F, left distal part of G1 (dorso-lateral view) (denuded). Scales: A = 5.0 mm; B–D, H = 2.0 mm; E–G, I, J = 1.0 mm; K, L = 0.5 mm.

Fig. 43. Vulva. A, Chiromantes haematocheir, female (27.0 × 23.7 mm) (ZRC 2002.0225), Japan; B, Orisarma dehaani, female (20.4 × 17.8 mm) (ZRC 2012.0057), Japan; C, Orisarma intermedium, female (31.8 × 28.4 mm) (ZRC 2013.0140), Japan; D, Orisarma patshuni, female (20.5 × 18.1 mm) (ZRC 2014.0817), Hong Kong; E, Danarma obtusifrons, female (15.7 × 11.6 mm) (UF-FLMNH 14837), Hawaii; F, Danarma eurymerus, paratype ovigerous female (18.0 × 13.4 mm) (ZRC 2012.0956), Taiwan; G, Cristarma eulimene, female (15.6 × 12.8 mm) (ZRC 1968.1.22.3), Mozambique; H, Cristarma ortmanni, female (13.1 × 10.2 mm) (ZRC 2000.1783), Kenya; I, Trapezarma angolense, female (18.2 × 14.3 mm) (ZRC 2015.0297), Cameroon; J, Platychirarma buettikoferi, ovigerous female (11.3 × 9.1 mm) (ZRC 2015.0298), Cameroon.