Clistocoeloma suvaense Edmondson, 1951

Ng, Bee Yan Lee Ngan Kee & Ng, Peter K. L., 2023, On the identities of the sesarmid crabs, Sesarma villosum A. Milne-Edwards 1869, and Clistocoeloma suvaense Edmondson, 1951, with the description of a new species from the West Pacific (Decapoda, Brachyura, Thoracotremata), Zootaxa 5318 (2), pp. 217-236 : 221-224

publication ID	https://doi.org/ 10.11646/zootaxa.5318.2.3
publication LSID	lsid:zoobank.org:pub:9EDAB87A-F55E-44C0-A6DD-60CC712C0DA3
DOI	https://doi.org/10.5281/zenodo.8168985
persistent identifier	https://treatment.plazi.org/id/C4481C7D-FFF3-FFD3-FF30-FF29FDD1EE90
treatment provided by	Plazi
scientific name	Clistocoeloma suvaense Edmondson, 1951
status

Treatment

Clistocoeloma suvaense Edmondson, 1951 View in CoL

( Figs. 2A View FIGURE 2 , 3A–F View FIGURE 3 , 4A–C View FIGURE 4 , 5C, D View FIGURE 5 , 6A–C View FIGURE 6 , 8A, B View FIGURE 8 , 9E–H View FIGURE 9 , 10A–H View FIGURE 10 )

Clistocoeloma suvaense Edmondson, 1951: 238–241 View in CoL , figs. 37a–i, 38 [type locality: reef in Suva Habor, Fiji].

Clistocoeloma suvaense View in CoL — Rahayu & Takeda 2000: 38 (list).— Komai et al. 2004: 41 (list).— Ng et al. 2008: 220 (list).

Type material. Holotype: male (21.0 × 18.8 mm) ( BPBM 3976 About BPBM ), Suva , Fiji, no collection data.

Other material examined: Fiji: 1 male (18.8 × 16.9 mm) ( ZRC 2022.0985 View Materials ), river mouth, Navaca mangrove, Taveuni Island, Fiji, 16°05’19”S 179°05’48”E, coll. B.Y. Lee, S. Choy & B. Rashni, 26 July 2019. GoogleMaps — 1 male (17.8 × 16.3 mm) ( ZRC 2022.0986 View Materials ), mangrove at Suva Point Beach, near My Suva Picnic Park and Suva City Council Park, Fiji, 18°00’28”S 178°02’42”E, coll. B.Y. Lee & B. Rashni, 22 July 2019 GoogleMaps .— 1 male (12.1 × 10.9 mm) ( ZRC 2022.0987 View Materials ), Bure Bure mangrove, Naqai Creek , near Naqai Bridge , Taveuni Island, Fiji, 16°04’28”S 179°05’16”W, coll. B.Y. Lee, S. Choy & B. Rashni, 25 July 2019 GoogleMaps .— 2 males (13.7 × 12.2 mm, 12.5 × 11.4 mm), 1 female (13.3 × 11.9 mm) ( ZRC 2022.0988 View Materials ), river mouth, Navaca mangrove, Taveuni Island, Fiji, 16°05’19”S 179°05’48”E, coll. B.Y. Lee, S. Choy & B. Rashni, 26 July 2019 GoogleMaps .— 2 males (17.1 × 15.5 mm, 15.2 × 14.2 mm), 2 ovigerous females (16.6 × 15.0 mm, 16.2 × 14.5 mm), 1 female (18.7 × 17.0 mm) ( ZRC 2022.0989 View Materials ), mangrove at Suva Point Beach , near My Suva Picnic Park and Suva City Council Park, Fiji, 18°00’28”S 178°02’42”E, coll. B.Y. Lee & B. Rashni, 22 July 2019 GoogleMaps . Samoa: 1 male (16.2 × 14.3 mm) ( ZRC 1973.11.2.490) Upolu , coll. Godeffroy Museum.

Diagnosis. Carapace slightly wider than long, almost square; postfrontal lobes distinct, divided by longitudinal grooves; median pair broad, prominent, nearly equal in proportion; distant pair broad, prominent, nearly equal in proportion ( Figs. 2A View FIGURE 2 , 3A View FIGURE 3 , 4A View FIGURE 4 ). Anterolateral margin of carapace with distinct external orbital angle, blunt second tooth blunt separated by distinct shallow groove from external orbital tooth; posterolateral margin convex ( Figs. 2A View FIGURE 2 , 3A View FIGURE 3 , 4A View FIGURE 4 ). Inner orbital angle present, truncate, slight gap between inner orbital angle and frontal margin ( Figs. 3C View FIGURE 3 , 4C View FIGURE 4 ). Chelipeds dorsal surface of dactylus of chela with 22–27 evenly spaced tubercles, proximal tubercles small, increasing in size medially, decreasing in size distally ( Figs. 3E View FIGURE 3 , 5C View FIGURE 5 ); absent or weak granules in female and juveniles; presence of single longitudinal pectinated ridge with 33–36 chitinous comb-like tubercles on dorsal surface of chela; row of 9–11 granules behind pectinated ridge on chela ( Figs. 3E View FIGURE 3 , 5C View FIGURE 5 ); inner surface of palm granulated, with single vertical row of 6–10 granules in adult males ( Figs. 3F View FIGURE 3 , 5D View FIGURE 5 ); absent in females and juveniles. P5 merus relatively short, wide, length approximately 0.39–0.46 times width ( Fig. 6A–C View FIGURE 6 ). G1 straight, distal region relatively wide; chitinous tip wide, short; tip with dense tufts of setae, single row of plumose setae on exterior margin; chitinous tip visible when denuded ( Figs. 9E–H View FIGURE 9 , 10A–H View FIGURE 10 ). Female vulvae with central operculum, ovate, slightly protruded; sternal vulvar cover slightly raised above operculum ( Fig. 8B View FIGURE 8 ).

Description. Carapace slightly wider than long, almost square; covered with dense coat of setae, with small tufts of setae resembling tubercles; carapace margin fringed with dense, short setae; carapace smooth when denuded. Postfrontal lobes distinct, divided by longitudinal grooves; median pair broad, prominent, nearly equal in proportion; distant pair broad, prominent, nearly equal in proportion ( Figs. 2A View FIGURE 2 , 3A View FIGURE 3 , 4A View FIGURE 4 ). Anterolateral margin of carapace with distinct external orbital angle, blunt second tooth blunt separated by distinct shallow groove from external orbital tooth; posterolateral margin convex ( Figs. 2A View FIGURE 2 , 3A View FIGURE 3 , 4A View FIGURE 4 ). Inner orbital angle present, truncate, slight gap between inner orbital angle and frontal margin ( Figs. 3C View FIGURE 3 , 4C View FIGURE 4 ).

Antenna short. Antennules folding transversely. Third maxilliped with merus relatively ovate. Epistomial margin relatively narrow ( Figs. 3C View FIGURE 3 , 4C View FIGURE 4 ).

Chelipeds subequal in size; large, robust in male; outer surface of palm smooth when denuded; dorsal surface of carpus with small tufts of setae resembling tubercles, smooth when denuded; dorsal surface of dactylus of chela with 22–27 evenly spaced tubercles, proximal tubercles small, increasing in size medially, decreasing in size distally ( Figs. 3E View FIGURE 3 , 5C View FIGURE 5 ); absent or weak granules in female and juveniles. Presence of single longitudinal pectinated ridge with 33–36 chitinous comb-like tubercles on dorsal surface of chela; row of 9–11 granules behind pectinated ridge on chela ( Figs. 3E View FIGURE 3 , 5C View FIGURE 5 ). Inner surface of palm granulated, with single vertical row of 6–10 granules in adult males ( Figs. 3F View FIGURE 3 , 5D View FIGURE 5 ); absent in females and juveniles.

P2–P5 with dense coat of setae, with small tufts of setae resembling tubercles, longer setae on dorsal and ventral margins except distal portion of dactylus ( Figs. 2A View FIGURE 2 , 4A View FIGURE 4 ); P5 merus relatively short, wide, length approximately 0.39–0.46 times width ( Fig. 6A–C View FIGURE 6 ).

Male thoracic sternum covered with short setae, smooth when denuded; sternites 1 and 2 fused, with suture between fused sternites 3 and 4; sternopleonal cavity extends to edge sternites 1 and 2. Male pleon wide, stout, long setae fringed pleon margin; somite 3 widest; somite 6 with curved edge; telson wide, dome-shaped ( Figs. 3B, D View FIGURE 3 , 4B View FIGURE 4 ); male pleonal locking mechanism absent, without tubercle on sternite 5.

G1 straight, distal region relatively wide; chitinous tip wide, short; tip with dense tufts of setae, single row of plumose setae on exterior margin; chitinous tip visible when denuded ( Figs. 9E–H View FIGURE 9 , 10A–H View FIGURE 10 ). G2 shorter than G1, slightly curved, tip rounded.

Female pleon rounded, relatively wider than long; telson dome-shaped ( Fig. 8A View FIGURE 8 ). Vulvae with central operculum, ovate, slightly protruded; sternal vulvar cover slightly raised above operculum ( Fig. 8B View FIGURE 8 ).

Colouration. Chelipeds pale yellow fingers with pale orange to reddish palm ( Fig. 2A View FIGURE 2 ). In life, entire crab covered in thick layer of mud.

Remarks. Clistocoeloma suvaense was described by Edmondson (1951) based on one male and one female specimen collected from a reef in Suva Harbour. He compared it with other species that were recognised in Clistocoeloma at the time, i.e., C. balansae . C. merguiense and C. tectum ( Rathbun, 1914) . Clistoceoloma villosum was not treated or discussed as it was not in the genus at the time. Edmondson (1951) actually had three specimens from the Bishop Museum, two of which were collected from Suva Habour, Fiji, while one male specimen was collected from a Samoan reef. While Edmondson (1951) was certain that the two Fijian specimens belonged to his new species, he was more doubtful about the Samoan one; noting that the latter had no distinct lobes on the anterolateral margins (lobes present on the anterolateral margins of C. suvaense s. str.) and the dorsal surface of the dactylus of the male chela with 16 granules (with 25 granules in C. suvaense s. str.). We have not examined Edmondson’s (1951) Samoan specimens, but his observations match exactly what is known for C. villosum , we believe they are conspecific.

Clistocoeloma suvaense is known with certainty only from its type locality, although there is one specimen also from Samoa (see below) and published records from Singapore ( Wee & Ng 1994; Tan & Ng 1994). In addition to the lectotype specimen of C. villosum , another Wroblewsky specimen originally from the Godeffroy Museum was found in the ZRC, although how it got there is not known, possibly from the time R. Serène was based in Singapore in the 1960s. It is noteworthy that during that time, Serène was revising the IWP Sesarmidae with Soh Cheng Lan (e.g., see Serène & Soh 1970) and he had gathered material in Singapore for this work. The morphology of this Wroblewsky specimen, however, clearly matches what is here defined as C. suvaense and not C. villosum . Based on the specimen label, it has the same locality information as the lectotype of C. villosum . In addition to the very different morphology, the measurements of this specimen also do not match those listed in A. Milne-Edwards (1869) in his original description. It is unclear whether A. Milne-Edwards actually examined this specimen or if there is a mistake in the labels. There is also no mention of additional specimens of “ C. villosum ” in the eight sales catalogues of Godeffroy Museum that were published between 1864 and 1881 by curator J.D.E. Schmeltz other than that for the original specimen in A. Milne-Edwards (1896) or later papers by the author on the Godeffroy Museum collections (e.g. A. Mine-Edwards 1873a). For the moment, we accept the record of C. suvaense as being also present in Samoa. Even though both C suvaense and C. villosum are found together in Samoa, it is important to note that currently, no specimens of C. villosum has been found in Fiji. Recent collections there only found C. suvaense . Records of “ C. suvaense ” from Singapore by Wee & Ng (1994) and Tan & Ng (1994) belong to C. nobile n. sp. instead.

Although C. suvaense is superficially similar to C. villosum and C. nobile n. sp., they are relatively easy to distinguish, especially adult males. Clistocoeloma suvaense clearly differs from C. villosum s. str. in the presence of a distinct external orbital angle on the anterolateral margin of the carapace ( Figs. 2A View FIGURE 2 , 3A View FIGURE 3 , 4A View FIGURE 4 ) (the external orbital angle on the anterolateral carapace margin is not distinct and low in C. villosum ; Fig. 1A View FIGURE 1 ); the presence of a broad, rounded inner orbital angle ( Figs. 3C View FIGURE 3 , 4C View FIGURE 4 ) (the inner orbital angle is narrow and ovate in C. villosum ; Fig. 1C View FIGURE 1 ); possessing 25–26 granules on the dorsal surface of the dactylus of the adult male chela ( Figs. 3E View FIGURE 3 , 5D View FIGURE 5 ) (16 granules in C. villosum ; Fig. 5A View FIGURE 5 ); and the G1 is straighter with a proportionately broader distal portion ( Figs. 9E–H View FIGURE 9 , 10A–H View FIGURE 10 ) (G1 slightly curved with a narrower distal portion for C. villosum ; Fig. 9A–D View FIGURE 9 ). Fresh collections of C. suvaense from the type locality show that the species is not uncommon in Fiji, and all the recent specimens agree very well with the type material.

Ecological notes. It was mentioned that the specimens were collected from “a reef in Suva Harbor in 1933” ( Edmondson 1951: 240). Fresh material was collected from the back mangrove at a higher elevation and found on muddy substrate under large loose rocks in Suva and Taveuni Island, Fiji. Specimens were found with layer of mud covering the entire crab.

Distribution. Currently only known for certain from the type locality, Suva, as well as Taveuni Island, Fiji; the record from Samoa is uncertain.