Clistocoeloma balansae A. Milne-Edwards 1873
Creators: name: Lee, B. Y.
name: Ng, N. K.
name: Ng, L.
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Sesarmidae
Clistocoeloma
Clistocoeloma balansae

description: Clistocoeloma balansae A. Milne-Edwards, 1873
(Figs. 1–6)
Clistocoeloma balansae A. Milne-Edwards, 1873: 311, 312, 331, pl. 17: fig. 1, 1a–c (type locality Nouvelle Calédonie [= New Caledonia]).
Clistocoeloma balansae —Kingsley 1880: 219; De Man 1888: 195–196; De Man 1896: 339, 340, 342, 343; Alcock 1900: 429; Tesch 1917: 222–225, 231 (list), 260 (key); Shen 1933: 52, 54 (key); Chopra & Das 1937: 433, fig. 15d (list); Edmondson 1951: 240 (list); Hsueh & Huang 1996: 63 (list); Rahayu & Takeda 2000: 38 (list); Davie 2002: 221; Komai et al. 2004: 41; Ng et al. 2008: 220 (list).
Sesarma (Sesarma) tectum Rathbun, 1914: 78, 79 [synonymy]
Sesarma (Sesarma) tectum —Estampador 1937: 537 (list); Estampador 1959: 94 (list).
Clistocoeloma tectum —Tesch 1917: 222–227, 231 (list), 260 (key), pls. 17: fig. 3, 3a–c; Shen, 1933: 53, 54 (key); Chopra & Das 1937: 433; Ward 1941: 2 (list); Edmondson 1951: 240; Hsueh & Huang 1996: 63 (list); Niem 1996: 332 (list); Rahayu & Takeda 2000: 35, 38; Komai et al. 2004: 41 (list); Ng et al. 2008: 220 (list).
Material examined: 1 male (20.7 × 19.7 mm) (MNHN B10912) [lectotype, herein designated], New Caledonia, coll. B. Balansa, no collection date.— 1 female (18.9 × 17.3 mm) (MNHN B10912) [paralectotype, herein designated], New Caledonia, coll. Balansa, no collection date.— 1 female (19.5 × 18.6 mm) (USNM 45766) [holotype of Sesarma (Sesarma) tectum Rathbun, 1914], off northern Luzon, Palaui I., Port San Vicente, Philippines, coll. 14 November 1908.—Additional material: 1 male (11.8 × 11.2 mm), 1 female (16.5 × 15.3 mm) (ZRC 2009.0898), Kawasan, Matutinao, Cebu, Philippines, coll. H. C. Liu et al., 12 January 2001.— 1 male (23.3 × 22.6 mm) (ZRC 2009.0900), Gilatilan, south of Matutinao, Cebu, Philippines, coll. H. C. Liu et al., 12 February 2001.— 1 male (15.9 × 15.5 mm), 2 females (18.7 × 17.8 mm, 17.2 × 16.9 mm) (ZRC 2012.702), PANGLAO 2004 Expedition, station M45, adjacent to Nipa palms, freshwater spring on bank, Abatan River, Bohol I., Philippines (9º43.9’N, 123º53.4’E), coll. PANGLAO 2004 Expedition, 29 June 2004.— 1 male (7.4 × 7.1 mm) (ZRC 2012.703), PANGLAO 2004 Expedition, station M57, fringe mangrove, Sungcolan inlet, Panglao I., Philippines (9º38.0’N, 123º49.9’E), coll. PANGLAO 2004 Expedition, 4 July 2004.— 3 males (15.5 × 14.7 mm, 12.3 × 11.7 mm, 9.0 × 8.5 mm), 2 females (21.7 × 21.2 mm, 14.0 × 21.2 mm) (ZRC 2012.704), Kawasan Fall, Matutinau, Cebu, Philippines, coll. P. K. L. Ng et al., 30 July 2003.— 1 female (17.5 × 16.5 mm) (ZRC 2012.700), station VM4, intertidal, between Rose point and Nasouli River, Vanuatu (15º34.9’S, 167º01.8’E), coll. SANTO 2006 Expedition, 11 September 2006.— 1 male (11.2 × 10.5 mm) (ZRC 2012.701), station VM15, estuarine mangrove, Wambu River, Vanuatu (15º33.5’S, 167º08.4’E), coll. SANTO 2006 Expedition, 17 September 2006.
Diagnosis. Carapace almost square, covered with dense coat of setae, among which stands small tufts of setae resembling tubercles; denuded carapace with uneven surface, with pronounced tubercles (Figs. 1 A, 2A, 3A). Postfrontal lobes distinct, divided by deep longitudinal grooves, distal lobes separated into 2 distinct tubercles by shallow groove (Figs. 1 A, 2A, 3A). Inner orbital angle present, pronounced (Figs. 1 C, 2C). Anterolateral margin with 3 triangular teeth, inclusive of external orbital angle. Cheliped with dorsal surface of carpus with dense coat of setae; covered with tubercles when denuded; single longitudinal pectinated ridge present on dorsal surface of chela, with about 30 fine closely spaced teeth; dorsal surface of movable dactylus of chela with 14–20 tubercles (Fig. 4).
Inner surface of chela granular, with single vertical row of approximately 9 granules in adult males (Fig. 4 B). Tubercle present behind pectinated ridge on inner surface of male chela (Figs. 4 A, 4C). Tip of G1 with dense tufts of setae, single row of setae on exterior margin of G1; wide chitinous tip visible when denuded (Figs. 5 B–D).
Redescription. Carapace slightly wider than long, almost square, covered with dense coat of setae, among which stands small tufts of setae resembling tubercles. Denuded carapace with uneven surface; pronounced tubercles on carapace defined by deep grooves. Postfrontal lobes distinct, divided by deep longitudinal grooves, median pair broad, prominent, distal lobes split into 2 distinct tubercles by shallow groove. Regions relatively well defined by tubercles on carapace. Inner orbital angle present, pronounced.
Anterolateral margin with 3 triangular teeth, inclusive of external orbital angle: third tooth largest, roundest; posterolateral margin convex. Entire margin of carapace fringed with dense, short setae, which obscures teeth.
Chelipeds equal or subequal in size; large, robust in males; small, slender in females; chela approximately 2.1 times dactylus length. Merus covered with dense coat of setae, smooth when denuded. Dorsal surface of carpus covered with small tufts of setae resembling tubercles; revealing tubercles when denuded. Outer surface of palm smooth when denuded. Dorsal surface of movable dactylus of chela with 14–20 tubercles, evenly spaced, proximal tubercles small, increasing in size medially, decreasing in size distally. Tubercles on movable dactylus of chela present in female but smaller, less distinct. Single longitudinal pectinated ridge on dorsal surface of chela, with about 30 fine teeth. Inner surface of chela granular, with single vertical row of approximately 9 granules in adult males. Granules on inner surface of palm not obvious or absent in juveniles, females. Tubercle present behind pectinated ridge on inner surface of male chela; less distinct on females.
Walking legs covered with dense coat of setae, with small tufts of setae resembling tubercles, smooth when denuded; longer setae on dorsal, ventral margins of entire leg except dactylus; meri with deep groove subdistally. Third walking leg: merus approximately 2 times longer than wide; combined length of carpus, propodus slightly shorter than merus (c. 0.8 times); propodus approximately 2 times longer than wide.
Thoracic sternum setose, covered with short setae. Abdomen of male narrow, widest at somite 3; long setae fringing margins. Male abdomen with telson approximately 1.2 times longer than wide. Female abdomen wide, rounded; telson half embedded in somite 6. Male G1 stout, but relatively slender; subdistally wide. Tip of male G1 with dense tufts of setae, single row of setae on exterior margin; wide chitinous tip revealed when denuded.
Ecological notes. This species is found in mangroves. The dense coat of setae on the carapace and legs of the crab is similar in colour as the mud that the crab inhabits, suggesting a possible form of camouflage. According to the collector, this species is very rare in its type locality [“ Cette espèce est fort rare à la Nouvelle-Calédonie, où M. Balansa l’a trouvée au milieu des Palétuviers ”] (A. Milne-Edwards 1873: 312).
Distribution. New Caledonia, Vanuatu and, Philippines (Panglao and Palaui Islands).
Remarks. Alphonse Milne-Edwards (1873: 311–312) made clear in the description that he had at least one male and one female specimen. All extant specimens are syntypes because no holotype was indicated. In the MNHN, there is one dried male and one dried female specimen with the former corresponding in size to the specimen measured by A. Milne-Edwards (1873: 312). The dried male specimen measuring 20.7 × 19.7 mm (MNHN B10912a) is herein designated as the lectotype of C. balansae.
Sesarma (Sesarma) tectum Rathbun, 1914, was described on the basis of a large female specimen (19.5 × 18.6 mm; USNM 45766) from Palaui I., Luzon, Philippines. While it was described at length, no figure was provided. The species has never been figured. Tesch (1917) identified one male and three females from Talaud I. (= Talaut Archipelago, off northern Sulawesi) and one female from Nias I. (western Sumatra, Indian Ocean) as Sesarma (S.)
tectum although he did not examine Rathbun’s type. Tesch also transferred the species to Clistocoeloma. Although he was confident in his identification, Tesch (1917: 223) commented “ Cl. tectum bears a very great resemblance to Cl. balansae A. Milne-Edwards, on account of the carapace being quadrate, and the distance between the outer orbital angles only slightly or not at all exceeding the length of the carapace, and the external postfrontal lobes being subdivided into two small tubercles. It differs by the course of the upper orbital border that is not waved, by the tubercles on the carapace, the shape of the abdomen of the 3 and probably by some other characters”. Tesch must have based his observations on the different male abdominal shapes on his single male specimen and the figure in A. Milne-Edwards (1873) since Rathbun’s (1914) type was a female. While the form of the supraorbital margin is somewhat variable, the male abdomen as figured by A. Milne-Edwards (1873: pl 17, fig. 1b) is unusual, being evenly triangular, unlike that of typical Clistocoeloma (and most sesarmids) that is more quadrate with somite 6 relatively broader (e.g., in the present C. balansae, Figs. 3 B, 6A). The telson of the dried lectotype male of C. balansae is damaged by glue, but the shape of the other somites (Fig. 1 B) is typical for many Clistocoeloma species and does not match the drawing in A. Milne-Edwards (1873: pl. 17 fig. 1b). The abdomen of “ C. balansae ” figured by A. Milne-Edwards almost certainly belongs to a species of the family Varunidae and was probably just mislabeled; this seems especially likely since two varunids were depicted on the same plate, viz. Ptychognathus barbatus (A. Milne-Edwards, 1873) (as Gnathograpsus barbatus) and Pseudograpsus elongatus (A. Milne- Edwards, 1873) (as Heterograpsus elongatus). Other than the shape of the male abdomen, we can discern no other major differences between the specimens described by Tesch (1917) and the present specimens of C. balansae from New Caledonia, Vanuatu and the Philippines and we provisionally treat his records as this species. The male specimen from Talaud I. is likely to be real C. balansae as these islands are just south of the Philippines. Tesch’s (1917) specimens from Nias will need to be re-examined as this locality is in the Indian Ocean.
The holotype of S. (S.) tectum is one of the largest Clistocoeloma specimens known and can be separated from C. balansae only by the form of the posterior carapace margin. The margin is slightly sinuous to almost straight in the typical C. balansae (Figs. 3 C, D) whereas, the posterior carapace margin is deeply concave medially in C. tectum (Fig. 2 D). A careful examination of the posterior carapace margin of the holotype female of C. tectum shows that the margin is slightly asymmetrical, indicating that an injury had occurred previously and the present form is the result of uneven growth after healing. Other than this feature, it agrees with C. balansae in all other diagnostic characters. As such, we synonymise S. (S.) tectum Rathbun, 1914, with C. balansae A. Milne-Edwards, 1873.
description: Published as part of Lee, B. Y., Ng, N. K. & Ng, L., 2013, On the identity of Clistocoeloma balansae A. Milne-Edwards, 1873, and C. tectum (Rathbun, 1914), with description of a new species from the West Pacific (Crustacea: Decapoda: Sesarmidae), pp. 420-432 in Zootaxa 3641 (4) on pages 421-428, DOI: 10.11646/zootaxa.3641.4.8, http://zenodo.org/record/222413