Ethusina macrospina, 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 : 77-81

Ethusina macrospina , new species

( Figs. 8-11 )

fused; segment 6 subrectangular, broader than long, lateral margins almost straight; telson triangular. G1 broadly Cshaped, distal part conical, G2 opening subterminal.

Etymology. – The name alludes to the large external orbital spine of the species. The name is used as a noun in apposition.

Remarks. – The present species bears a remarkable resemblance to Ethusa indica Alcock, 1894 , in carapace form, but the immovable eye and large basal antennular segment clearly identifies it as a species of Ethusina . The length of the slender external orbital spine, which extends well beyond the tip of the frontal tooth, is diagnostic for this Ethusina species. The length of this tooth is reminescent of those in E. challengeri ( Miers, 1886) (34 37’N 140 32’E), E. gracilipes ( Miers, 1886) ( Philippines, Japan), E. investigatoris Alcock, 1896 ( Philippines, China), E. serenei ( Sakai, 1983) (South China Sea), E. longipes Chen, 1987 ( Madagascar) , and E. paralongipes Chen, 1993 ( New Caledonia), but in none of these species does the external

Material examined. – Holotype – male, 7.2 by 7.3 mm ( NTOU), Station CD 135, 22 17.21’N, 120 0.28’E, 961-1112 m, coll. TAIWAN 2000, R. V. “Fishery Researcher 1”, 22 Nov.2001.

Paratypes – 2 females, 9.4 by 10.7 mm ( NTOU), 8.6 by 9.2 mm ( ZRC), same data as holotype ; 1 female, 9.8 by 10.1 mm ( NTOU), Station CD 134, 22 16.56’N, 120 06.11’E, 736-1040 m, coll. TAIWAN 2000, R. V. “Fishery Researcher 1”, 22 Nov.2001 ; 1 male, 6.8 by 7.3 mm ( ZRC), Station CD 141, 22 12.04’N, 119 59.96’E, 1110- 985 m, 24 November 2001 ; 1 female, 10.7 by 11.2 mm ( ZRC), 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 .

Diagnosis. – Carapace slightly longer than broad; dorsal surface gently convex, appears almost smooth without magnification, regions not well defined. Front not prominently projecting anteriorly, with 4 teeth; median teeth low, reaching only to about half length of relatively short lateral teeth, directed anteriorly, separated by distinct concavity; lateral teeth directed slightly obliquely inwards, separated from median teeth by shallow 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 almost straight. Chelipeds subequal; fingers slightly longer than palm; cutting edges with low teeth. P2 and P3 smooth, glabrous; P3 longest, merus 6.9-7.5 times as long as wide, propodus 5.2-5.7 times as long as wide; dactylus not very elongate. Male abdomen with segments 3-5 completely orbital spine project so far forwards. The P2 and P3 of all these four species, however, are also much longer and more slender than those of E. macrospina , and easily distinguishes the latter, with those of E. challengeri exceptionately long (cf. Miers, 1886). The regions just behind the frontal teeth of E. gracilipes , E. serenei , E. longipes and E. paralongipes appear to be distinctly swollen, but in E. macrospina , this area is not prominently inflated. The median frontal teeth of these four species are also much more well developed, longer and more spiniform than those of E. macrospina (see Miers, 1886; Serène & Lohavanijaya, 1973; Sakai, 1983; Chen, 1987, 1993).

The relatively good series of specimens of E. macrospina allow some insight into variation in the species. The proportions of the P2 do vary a bit, but not very substantially (merus and propodus 6.9-7.5 and 5.2-5.7 times as long as wide respectively), and does not affect the comparisons with other taxa. The strength of the external orbital spine varies a bit in strength and orientation. In the holotype male and some paratype females (e.g. 9.8 by 10.1 mm, Station CP 38) ( Figs. 8A, B , 9C , 10A, 11A ), the external orbital spine is very long and slender, and directed obliquely outwards at an angle of almost 45. In the paratype male and other females, the spine is relatively shorter, and directed more anteriorly ( Figs. 8C , 9A, B, D ).

Figures

Fig. 8. Ethusina macrospina, new species. A, B, holotype male, 7.2 by 7.3 mm (NTOU); C, paratype male, 6.8 by 7.3 mm (ZRC). A, overall view; B, C, carapace.

Fig. 9. Ethusina macrospina, new species. A, paratype female, 8.6 by 9.2 mm (ZRC); paratype female, 9.4 by 10.7 mm (NTOU); C, paratype female, 10.7 by 11.2 mm (ZRC); D, paratype female, 9.8 by 10.1 mm (NTOU).

Fig. 11. Ethusina macrospina, new species. A-E, paratype female, 10.7 by 11.2 mm (ZRC); F, paratype female, 8.6 by 9.2 mm (ZRC); G, paratype male, 6.8 by 7.3 mm (ZRC). A, carapace; B, left orbit, antenna and antennule; C, F, G, right P2; D, right P5; E, right chela. Scales: A, C, F, G = 5.0 mm; B = 2.0 mm; D, E = 1.0 mm.