Ethusina taiwanensis, Ng & Ho, 2003

Ng, Peter K. L. & Ho, P. - H., 2003, On The Deep-Water Dorippid Crabs Of The Genus Ethusina Smith, 1884 (Crustacea: Decapoda: Brachyura) From Taiwan, Raffles Bulletin of Zoology 51 (1), pp. 71-85 : 72-74

Ethusina taiwanensis , new species

( Figs. 2 , 3 )

Material examined. – Holotype - male, 7.7 by 9.5 mm ( NTOU), Station CP 61, 24 o 47.5’N, 122 17.4’E, 1134 m, coll. TAIWAN 2000, R. V. “Fishery Researcher 1”, 4 Aug.2000.

Paratype – 1 male, 7.7 by 8.7 mm ( ZRC), Station CD 129, 22 5.89’N, 121 5.21’E, 1271-1275 m, coll. TAIWAN 2001, R. V. “Ocean Researcher 1”, 21 Aug.2001 .

Diagnosis. – Carapace longer than broad; dorsal surface gently convex, appearing smooth without magnification, regions not well defined. Front not prominently projecting anteriorly, with 4 teeth; median teeth not reaching tips of lateral teeth, directed obliquely outwards, separated by prominent concavity; lateral teeth directed anteriorly, separated from median teeth by deep concavity. External orbital spine acutely triangular, directed obliquely outwards, tip not or just reaching bases of median frontal teeth. Lateral carapace margins gently sinuous, with posterior part distinctly convex. Posterior carapace margin gently concave. Chelipeds subequal; fingers slightly longer than palm; cutting edges with low teeth. P2 and P3 smooth, glabrous; P3 longest, merus 7.0-7.1 times as long as wide, propodus 5.3-5.4 times as long as wide; dactylus elongate. Male abdomen with segments 3-5 completely fused, only traces of median sutures just visible; segment 6 rectangular, broader than long, lateral margins distinctly convex; telson semicircular, lateral margins gently convex. G1 gently curved, inner subdistal margin with short perpendicular projection.

Etymology. – The species is named after the island of Taiwan.

Other material – 1 female, 8.8 by 9.5 mm ( IOCAS), Station 16, Spratly Islands ( Nansha Islands ), South China Sea, 1080 m, coll. 21 Apr.1999 .

Diagnosis. – Carapace longer than broad; dorsal surface gently convex, with scattered low granules visible without magnification, regions not well defined. Front not prominently projecting anteriorly, with 4 teeth; median teeth short, reaching only to about half length of lateral teeth, directed anteriorly, separated by distinct concavity; lateral teeth directed slightly obliquely outwards, separated from median teeth by concavity. External orbital spine very slender, acutely triangular, directed obliquely outwards, tip reaching beyond tips of median frontal teeth. Lateral carapace margins gently sinuous, with posterior part distinctly convex. Posterior carapace margin gently concave. Chelipeds subequal; fingers slightly longer than palm; cutting edges cutting edges with low teeth. P2 and P3 smooth, glabrous; P3 longest, merus 9.7 times as long as wide, propodus 7.5 times as long as wide; dactylus very slender, very elongate. Male not known.

Remarks. – With regards to the carapace form, the present specimens seem to be close to E. desciscens Alcock, 1896 (type locality Laccadives, Indian Ocean). That species has since been reported from other parts of the Indian Ocean, Philippines, Indonesia, China and Vanuatu (see Chen, 1986a, b, 1987, 1993, 1997, 2000). The two present specimens from Taiwan, however, differ from E. desciscens s. str. in having relatively shorter P2 and P3, the frontal region protrudes anteriorly less prominently, the male telson is semicircular in shape (vs. triangular), the lateral margins of male abdominal segment 6 are prominently convex (vs. gently concave) and the G1 is relatively more slender and gently curved, with a distinct subdistal projection (vs. straighter, stouter and entire) (cf. Alcock, 1896; Alcock & MacGilchrist, 1905: Pl. 72 fig. 2; Chen, 1987: 689, Fig. 7 , Pl. 2 fig. F). As such, it seems best to refer these specimens to a new species, here named E. taiwanensis . The carapace features of E. taiwanensis actually agree well with what Chen (1986b: 136, Fig. 15.71 -73) identified as “ E. desciscens ” from China, and they may well be conspecific. In fact, the identity of all the specimens from the Pacific that had been identified as E. desciscens by previous reports should be redetermined; some may well be E. taiwanensis instead.

Figures

Fig. 2. Ethusina taiwanensis, new species. A, B, holotype male, 7.7 by 9.5 mm (NTOU); C, paratype male, 7.7 by 8.7 mm (ZRC). A, overall view; B, C, carapace.

Fig. 3. Ethusina taiwanensis, new species. Holotype male, 7.7 by 9.5 mm (NTOU). A, carapace; B, left orbit, antenna and antennule; C, left chela; D, right P2; E, right P5; F, male abdominal segments 3-6 and telson (3-5 fused); G, H, left G1 (tip of G2 protruding from subdistal opening); I, distal part of left G1 with G2 distal segment protruding from G1 opening. Scales: A, D = 5.0 mm; B, C, E-H = 1.0 mm; I = 0.5 mm.

Fig. 7. Ethusina chenae, new species. Holotype female, 11.0 by 10.5 mm (NTOU). A, carapace; B, left orbit, antenna and antennule; C, right P2; D, right P5; E, right chela. Scales: A, C = 5.0 mm; B, D, E = 1.0 mm.

Fig. 15. Ethusina saltator, new species. Holotype male, 5.9 by 6.8 mm (NTOU). A, carapace; B, right P2; C, right P5; D, dactylus and propodus of right P5; E, left chela; F, male abdominal segments 3-6 and telson (3-5 fused); G, H, I left G1 (various views) (setae denuded); J, left G2. Scales: A-C, E = 2.0 mm; F = 1.0 mm; D, G-J = 0.5 mm.