Cavoportunus dubius Laurie 1906, comb. nov.
Creators: name: Ng, Peter K. L.
Publisher: name: Zenodo
Year: 2010
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Portunidae
Cavoportunus
Cavoportunus dubius

description: Cavoportunus dubius (Laurie, 1906) comb. nov.
(Figs. 1–4)
Neptunus (Achelous) dubia Laurie, 1906: 416, fig. 9.
Portunus (Achelous) dubius — Stephenson & Rees 1967: 20, fig 3. — Stephenson 1972a: 135. — Stephenson 1972b: 15, 38. – Stephenson 1976: 16. – Moosa 1981: 143, 147. — Crosnier 1984b: 401; 1985: 33, figs. 1a-e; 2002: 404. — Zarenkov 1994: 115. — Moosa 1996: 521. — Poupin 1996a: 31. — Neumann & Spiridonov 1999: 19. —– Ng et al. 2008: 151.
Portunus (Cycloachelous) yoronensis Sakai, 1974: 90. — Sakai 1976: 349, figs. 189a-d. — Ng et al. 2008: 151. (See Remarks)
Material examined. Lectotype (here designated): male (10.2 × 8.1 mm) (NHM 1907.5.22.320a), off Negombo, Sri Lanka or Gulf of Manaar, coral reef; 1 male paralectotype, broken up (NHM 1907.5.22.320b), same data as lectotype. Other material: 2 males (18.5 × 14.6 mm, 17.4 × 13.3 mm), 1 female (18.5 × 14.3 mm) (ZRC 2001.0627), Philippines, Bohol, Panglao Is., Balicasag Is., 50–500 m, tangle nets, 28 November 2001; 1 male (14.8 × 11.4 mm), 1 juv. male (9.7 × 7.3 mm), 1 female (13.4 × 10.2 mm) (WMNH-Na-Cr 0539), Japan, Wakayama, Kushimoto, Kamiura, 20 –30 m, November 1979; 1 female (13.0 × 10.2 mm) (NSMT-KY-08-15), Japan, Ogasawara Is., south of Chichi-jima Is., 27°03.846΄N 142°07.644΄E –27°03.663΄N 142°07.869΄E, 109- 97 m, dredge, coll. RV Koyo, 28 October 2008; 1 juv. male (8.2 × 6.5 mm) (NSMT-KY-08-18), Japan, Ogasawara Is., east of Chichi-jima Is., 27°05.014΄N 142°14.894΄E –27°04.881΄N 142°14.865΄E, 49– 48 m, dredge, coll. RV Koyo, 29 October 2008; 1 juv. male (8.4 × 6.7 mm) (NSMT-KY-08-26), west of Chichi-jima Is., Ogasawara Is,, Japan, 27°04.840΄N 142°08.934΄E - 27°04.980΄N 142°09.151΄E, 84-87 m, dredge, coll. RV Koyo, 30 October 2008; 1 juv. male (8.9 × 6.8 mm) (NSMT-KY-09-27), Japan, Ogasawara Is., east of Anijima-Seto Is.,, 27°06.292΄N 142°13.877΄E – 27°06.284΄N 142°14.012΄E, 81-83.4 m, 50 cm ORI biological dredge, coll. RV Koyo, 15 July 2009; 1 male (12.3 × 9.8 mm), 2 juv. males (9.8 × 7.9 mm, 11.2 × 9.0 mm) (NSMT-SY-09-18), Japan, Ogasawara Is., west off Chichi-jima Is., 27°06.11΄N 142°08.89΄E – 27°06.07'N 142°09.06'E, 101– 98m, 50cm dredge, coll. TRV Shinyo-Maru, 18 November 2009.
Diagnosis. Carapace hexagonal in shape, relatively long, width approximately 1.3 times length, dorsal surface glabrous, microscopically granular with distinct regions; only metagastric ridge distinctly visible, other ridges are indistinct as granules diffused into large areas (Figs. 1, 2 A, 4A). Frontal margin with 4 sharp teeth, protruding beyond inner supraorbital angles, directed dorsally; lateral teeth stronger, longer than median ones; inner supraobital angles rounded (Figs. 2 A, 4A). Upper orbital margin with single fissure (Figs. 1, 2 A, 4A), lower margin with acute forward-directed tooth (Fig. 2 B). Anterolateral margin with 9 teeth, first tooth stoutest, size of second to ninth teeth subequal (Figs. 2 A, 4A). Merus of third maxilliped produced anterolaterally, length to width ratio approximately 1.27; length to width ratio of ischium 1.57 (Figs. 2 C, 3C). Cheliped covered with fine granules; ventral margin with squamiform markings; merus with 3 or 4 spines on anterior margin, a single spine at distal end of posterior margin; carpus with sharp spine on internal angle, outer surface with carina leading to spine; manus with 3 spines, one at wrist articulation, 2 on inner, outer margins of upper surface at distal end; outer surface with 3 granular costae at lower half; the first costa highly raised; movable fingers slender, as long as manus (Figs. 2 A, B, 3A, B). Fifth walking legs with short merus, posterior margin with fine denticles; propodus with fine, short, dense setae; without spines (Figs. 1, 2 A, B). Male abdomen triangular, with tapering lateral margins, converging towards posteror; posterior margin of somite 3 convex with median cleft; lateral margins of somite 4 evenly convex; lateral margins of somite 5 slightly convex (Figs. 2 B, 4B). Median line present on thoracic sternites 5 to 8 of both sexes. Male adominal holding system with prominent spur-like press-button on thoracic sternite 5 next to the sternal suture 5/6 (Figs. 3 D, 4C), present also in female and juveniles but relatively weaker (Figs. 3 G, H); sternite 8 of thoracic sternum of adult male with median groove, with 2 deep depressions (anterior larger) on each side to accommodate G1 (Figs. 3 D, 4C). G1 very short, relatively stout, S-shaped; basal part relatively slender, not dilated; subdistal part distinctly dilated, forming large lobe-like process; distal part rounded, with distinct flattened folds on tip (Figs. 3 E, 4D). G2 elongated, tapering, about four-fifths length of G1, bilobed tip (Figs. 4 E, F). Penis coxal, long, slender, proximally lodged between 2 raised processes of sternite 8 (Fig. 3 D). Vulvae mostly surrounded by thick, whitish, crescent-shaped rim; salient, short, whitish sternal cover on outer margin; separate, small, round operculum (Fig. 3 G).
Variation. The adult female abdomen is ovate and covers much of the sternum, with the telson triangular (Fig. 3 F). In juvenile males, the G1s relatively smaller, with depressions on thoracic sternum less developed (Fig. 3 H).
Color. White to transparent, some areas with scattered orange dots, especially on the carapace and chelipeds (Fig. 1). Silvery iridescence is very distinct on the posterolateral junction of the carapace, protruding edges of the first two abdominal somites, upper surface of the movable finger, carina on the outer side and upper spines of the palm and the spine on the outer wrist.
Distribution. Indian Ocean, French Polynesia to Japan.
Remarks. Laurie (1906) listed two specimens in his material examined of his description, one from the Gulf of Manaar and one from off Negombo in Sri Lanka. No holotype was indicated so both are syntypes. He provided measurements of one specimen, with a carapace length of 13 mm (Laurie 1906: 416) but did not indicate where the specimen was from. He also provided figures of the left cheliped, both third maxillipeds, male abdomen and two G1s of one specimen (Laurie 1906: fig. 9) but did not indicate its size or locality. We have checked the type material but only one specimen is still intact, a male measuring 10.2 × 8.1 mm. There are parts of another specimen in the same specimen jar that corresponds exactly to the structures figured by Laurie (Fig. 3 A, B, C; Laurie 1906: fig. 9). Although the carapace and all other parts of this specimen are missing, we believe the 13 mm carapace length specimen listed by Laurie (1906) is probably the broken-up one. The intact specimen measures 8.1 mm in carapace length and is clearly smaller than the broken specimen. We hereby designate the complete specimen as the lectotype of Cavoportunus dubius (Laurie, 1906) (Figs. 2 A, 4A).
The provenance of the lectotype cannot be ascertained. Laurie (1906) did not indicate precisely where his two specimens came from, so the lectotype was from either the Gulf of Manaar or Negombo. The label with the types mentions only the Gulf of Manaar and its catalogue number suggests only one specimen, although there are clearly two specimens. In any case, the two type localities are very close to each other so it is probably not significant.
Portunus yoronensis was originally described from one male specimen collected from Yoron Is., Japan (Sakai 1974: 91) but the type specimen could not be found in the Japanese repositories that still hold his material or in the Senckenberg Museum, Frankfurt, where some of his own material is now kept. It is, however, possible it is mixed with material in other jars or has not been catalogued. On the basis of the descriptions and figures by Sakai (1974, 1976) as well as examination of recent specimens of this species from Japan, Portunus (Cycloachelous) yoronensis Sakai, 1974, is clearly a junior synonym of Neptunus (Achelous) dubia Laurie, 1906. Crosnier (1984b) had in fact synonymized P. yoronensis with P. dubius but this has not been widely recognized by other authors. We agree with his assessment.
Stephenson & Rees (1967) reported a male and a female of Cavoportunus dubius (as Portunus) from the Philippines, and noted that the "… abdomen of the single male in the present collection is narrower, and the ultimate segment is longer than figured by Laurie (1906, fig. 9) ". We have re-examined the type specimen of Cavoportunus dubius, which was used for the photographs in Laurie (1906: fig. 9), and somite 6 of the abdomen is actually not as short as figured by Laurie (1906: fig. 9). Its actual shape actually closely matches the figures of Stephenson & Rees (1967: fig. 3b). However, the figure by Stephenson & Rees shows the anterior margin of the third male abdominal somite (Stephenson & Rees 1967: fig. 3b) as almost straight, and not sinuous as those observed in other Cavoportunus dubius specimens or figures or photographs provided by other authors (Figs. 2 B, 4B). The observed differences are possibly due to the rather schematic and inaccurate figure of Stephenson & Rees (1967: fig. 3b).
description: Published as part of Ng, Peter K. L., 2010, A new genus of the family Portunidae (Crustacea: Decapoda: Brachyura) and the identity of Portunus (Cycloachelous) yoronensis Sakai, 1974, pp. 38-48 in Zootaxa 2677 on pages 41-45, DOI: 10.5281/zenodo.199230