Ethusina chenae, 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 : 75-76

Ethusina chenae , new species

( Figs. 6 , 7 )

Material examined. – Holotype – female, 11.0 by 10.5 mm ( NTOU), Station CP 39, 21 57.5’N, 121 03.2’E, 1316-1317 m, coll. TAIWAN 2000, R. V. “Fishery Researcher 1”, 1 Aug.2000.

Paratype – 1 female, 8.5 by 8.4 mm ( ZRC), with sacculinid, same data as holotype .

Diagnosis. – Carapace slightly broader than long; 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 lower than lateral ones, directed obliquely outwards, separated by distinct broad concavity; lateral teeth directed anteriorly, separated from median teeth by shallow concavity. External orbital spine acutely triangular, directed anteriorly or almost so, tip reaching level of tips of median frontal teeth. Lateral carapace margins gently sinuous, with posterior part distinctly convex. Posterior carapace margin almost straight. Chelipeds subequal; fingers slightly longer than palm; cutting edges with low teeth. P2 and P3 smooth, glabrous; P3 longest, merus 6.2 times as long as wide, propodus 5.2 times as long as wide; dactylus not very elongate. Male not known.

Etymology. – This species is named after Chen Hui-Lian, whose studies have set the stage for the present one.

Remarks. – The present new species resembles E. robusta ( Miers, 1886) in terms of the shape of the carapace, and to some degree, the form of the frontal teeth. However, the present two female specimens of E. chenae differ from E. robusta in having the median frontal teeth distinctly lower and blunter than the lateral teeth, the external orbital spine is directed only slightly obliquely outwards (vs. at an angle of about 45), the meri of the P2 and P3 are distinctly shorter proportionately, and the dactyli of the P4 and P5 are also prominently shorter proportionately (cf. Miers, 1886: pl. 29 fig. 2, of a female specimen). The figure and description of E. robusta by Miers (1886: 332, pl. 29 fig. 2) differs somewhat from that of the species figured by Chen (1986b, 2000). Chen’s (1986b: 133, figs. 62-66) figure of a female specimen from the East China Sea resembles that of Miers (1886), but the median frontal teeth are distinctly lower and broader, the external orbital teeth are not directed so obliquely outwards, and the dactyli of the P4 and P5 are prominently shorter. In her later study, Chen (2000: 430, Fig. 3 ) depicted a male which has somewhat straighter lateral carapace margins with more prominent and straighter external orbital teeth, and the dactyli of the P2-P5 are distinctly shorter than those figured by Miers (1886). It seems rather unlikely that there is sexual dimorphism in the proportions of the P2 and P3, and we have some doubts whether Chen’s material is really E. robusta s. str. (type locality Arafura Sea). In any case, it is clear that the present Taiwanese material cannot be referred to the E. robusta of Miers and/or Chen, and should be regarded as undescribed. Clearly a revision of this group of species is warranted.

Figures

Fig. 6. Ethusina chenae, new species. Holotype female, 11.0 by 10.5 mm (NTOU). A, overall view; B, carapace.

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. 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.