Cymonomus deforgesi Ahyong and Ng, 2009

Ahyong, Shane T. & Ng, Peter K. L., 2017, Zavreliella undetermined, Zoological Studies (Zool. Stud.) 56 (24), pp. 1-20 : 10-12

Cymonomus deforgesi Ahyong and Ng, 2009

( Figs. 4, 7E )

Cymonomus sagamiensis . - Takeda 2001: 224.

Cymonomus sp. 3 cf. valdiviae . - Nagai 1994: 51, 53, pl. 1, fig. 8.

Cymonomus deforgesi Ahyong and Ng 2009: 234 , figs. 1, 7A, B [type locality: E of Dingalan Bay, Luzon, Philippines].

Type material: HOLOTYPE: NMCR 29831, male (cl 6.2 mm, pcl 5.4 m, cw 5.7 mm), E of Dingalan Bay, Luzon , Philippines, 15°00.93'N, 123°12.33'E, 1160-1184 m, AURORA 2007 stn CP 2681, 23 May 2007 . PARATYPE: ZRC, 1 juvenile male (cl 3.1 mm, pcl 2.7 mm, cw 2.8 mm), off Aligbay Island, Bohol / Sulu Sea margin, 8°46.2'N, 123°16.1'E, 624-647 m, PANGLAO 2005, stn CP2384, 299 May 2005.

Other material examined: TAIWAN: ZRC, 1 male (cl 6.4 mm, pcl 5.5 mm, cw 6.0 mm), SW of Dongsha, 20°11.46-07.26'N, 116°20.14-21.51'E, 957-988 m, sandy bottom, trawl, ZhongSha 2015, stn CP4132, RV Ocean Researcher 1, 22 July 2015.

JAPAN: NSMT Cr13217, 1 male (cl 6.5 mm, pcl 5.6 mm, cw 6.4 mm), Tosa Bay, 842-861 m, RV Kotoka-Maru, stn K98-1-800, 20 Jan 1998; NSMT Cr13589, 1 ovigerous female (cl 7.2 mm, pcl 6.2 mm cw 6.8 mm), Tosa Bay, 800 m, RV Kotoka-Maru, stn K00-5-800, 8 May 2000; WPMNH #46, 4 mature females (cl 7.4 mm, pcl 6.5 mm, cw 7.3 mm to cl 7.9 mm, pcl 6.8 mm, cw 7.2 mm), 1 juvenile female (cl 4.9 mm, pcl 4.0 mm, cw 4.4 mm), S of Shionomisaki, Kii Peninsula, Wakayama Prefecture, 700 m, October 1998.

Description: Carapace quadrate, almost square, lateral margins slightly divergent; regions weakly indicated, cervical groove distinctly more pronounced in males than females, broadly V-shaped; with slender conical anteriorly directed anterolateral spine and similar anterolaterally directed spine on lateral margin behind anterolateral spine; lower pterygostomian region swollen; anterior and anterolateral surfaces with long, fine, wiry setae, other surfaces with sparse, short fine setae. Dorsal and lateral surfaces entirely covered with minute granules, with granules becoming larger and more elongate anterolaterally. Fronto-orbital margin (excluding rostrum and lateral projections) advanced beyond anterolateral margins, more pronounced in males than females; exceeding half anterior carapace width; outer orbital processes slender, elongate, directed anteriorly, situated below plane of rostrum, laterally spinulate, with acute apices, as long as or slight shorter than rostrum. Rostrum slightly longer than half-length of eyestalks; 0.15- 0.19 pcl; slender, tapering to acute apex, minutely granular laterally and dorsally. Eyestalks distinctly divergent, slender, flattened ventrally, granular and prominently spinulate, fused to carapace below rostral base but demarcation distinct, reaching anteriorly almost to end of antennular peduncle article 1; cornea apparently vestigial, not pigmented. Epistome surface with blunt tubercle mesial to base of antennules, small spine mesial to base of antenna, with small cluster of elongate granules at base of rostrum.

Antennular peduncle 1.21 pcl (male), 0.90- 1.00 pcl (female); article 1 granular laterally or minutely spinular; article 2 minutely granular; article 3 smooth. Basal antennal article fused to epistome; articles 2-4 irregularly granular or spinular.

Maxilliped 3 ischiobasis subquadrate, sparsely granular and spinular, with longitudinal sublateral groove; ischium and basis demarcated by faint groove. Merus slightly shorter than ischiobasis, length about 2.5 × width, tapering distally to rounded apex; surface and margins spinulate. Dactylus conical, unarmed; propodus and carpus spinulate. Exopod granular, reaching beyond carpo-meral articulation but not reaching end of merus of endopod.

Chelipeds (P1) equal in size and ornamentation, setose. Merus finely granular. Carpus finely granular, dorsal margin with 3 spines. Palm surfaces with fine granules and few scattered acute granules, flexor and extensor margins spinulate. Dactylus slightly longer than upper palm length; with proximal dorsal spines and granules; with faint longitudinal carina on outer surface, occlusal surfaces of dactylus and pollex crenulate, without gape when fingers closed.

Pereopods 2 and 3 sparsely setose; all articles except for dactylus finely granular; propodus and carpus with bluntly spinular extensor margins; merus with bluntly spinular extensor and flexor margins. Pereopod 3 longest, merus 1.35- 1.41 pcl (male), 0.99-1.09 pcl (female). Dactyli broadly curved, smooth, with longitudinal rib. Pereopod 3 dactylus as long as combined length of propodus and carpus.

Pereopods 4 and granular, minutely spinulate, sparsely setose; shorter than merus of pereopod 3; dactyli markedly shorter than propodi, falcate, with corneous apex and 4 or 5 obliquely inclined, corneous spines on flexor margin. Pereopod 5 merus, when folded against carapace, reaching midlength of carapace.

Thoracic sternite 3 pentagonal, about 1.5 × wider than long; lateral margins slightly convergent, irregular, surface granulate. Margins of sternites 4 and 5 granulate.

Abdomen of both sexes with margins and surface finely granular or minutely spinulate; pleotelson triangular, apex, bluntly rounded, length slightly exceeding half width.

Gonopod 1 distal article cannulate, forming copulatory tube, with moderately long distal setae. Gonopod 2 with articles fused; distomesial margin slightly hollowed, apex acute.

Remarks: Cymonomus deforgesi , previously known only from the Philippines, is herein reported from the northern South China Sea (Dongsha) and Japan. The specimens agree in most respects with the holotype, although we note that the relatively pronounced, broad V-shaped cervical groove that crosses the carapace (most pronounced in males), not clearly indicated on the original illustration of the holotype, is distinct in the holotype and other males. Cymonomus deforgesi is redescribed and refigured here including additional features not illustrated in the original account of the species ( Ahyong and Ng 2009). Adult females are recorded for the first time; they exhibit typical cyclodorippoid sexual dimorphism in the length of the walking legs as indicated by the proportionally shorter pereopod 3 merus: 1.4 pcl in males versus 1.0- 1.1 pcl in females. Also, the carapace is somewhat more inflated in mature females than in males, making the cervical groove less pronounced and fronto-orbital region appear slightly less anteriorly produced. The telson shape is similar in both sexes, though proportionally larger than in males.

Takeda’s (2001) C. sagamiensis from Tosa Bay (specimens examined herein) is clearly referable to C. deforgesi as is Nagai’s (1994) Cymonomus sp. 3 cf. valdiviae .

Distribution: Philippines and now from the northern South China Sea (Dongsha) and southern Japan (off Shionomisaki; Tosa Bay); 577-1184 m.

Figures

Fig. 4. Cymonomus deforgesi Ahyong and Ng, 2009. A-J: male holotype, cl 6.2 mm, pcl 5.4 mm, cw 5.7 mm, Philippines, NMCR 29831. K: female, cl 7.9 mm, pcl 6.8 mm, cw 7.1 mm, Japan, WPNHM #46. A, dorsal habitus; B, fronto-orbital region; C, right basal antennal spine; D, carapace tubercles of right anterolateral corner; E, right maxilliped 3; F, thoracic sternite 3; G, abdomen; H, K, telson; I, right gonopod 1, abdominal view; J, right gonopod 2, abdominal view. Scale bars: A, G = 2.0 mm; B, E, F, H = 1.0 mm; C, D, I-K = 0.5 mm. (A-C, E, G, I, J modified after Ahyong and Ng 2009: fig. 1).

Fig. 7. A, Cymonomus chani sp. nov., female holotype, pcl 7.9 mm, SW of Kaohsiung, Taiwan, NTOU; B, Cymonomus cognatus sp. nov., male holotype, pcl 6.4 mm, E of Su-Ao, Taiwan, NTOU; C, Cymonomus cognatus sp. nov., spent female, pcl 9.2 mm, SE of Macclesfield Bank, stn DW4102, AM P100611; D, Cymonomus curvirostris Sakai, 1965, ovigerous female, pcl 3.3 mm, off Miura, Sagami Bay, Japan, CBM (specimen not examined); E, Cymonomus deforgesi Ahyong and Ng, 2009, male, pcl 5.5 mm, SW of Dongsha, stn CP4132, ZRC. Photos: A, B, C, E (T.Y. Chan), D (T. Komai).