Ethusa abbreviata, Castro, 2005

Castro, Peter, 2005, Crabs of the subfamily Ethusinae Guinot, 1977 (Crustacea, Decapoda, Brachyura, Dorippidae) of the Indo-West Pacific region, Zoosystema 27 (3), pp. 499-600 : 510-512

Ethusa abbreviata n. sp.

( Fig. 2 )

Ethusa sexdentata – Chen 1985: 185, figs 5, 6, pl. 2, figs 1, 2; 1997: 622. — Chen & Sun 2002: fig. 100 (not E. sexdentata ( Stimpson, 1858)) .

Ethusa makasarica – Chen 2000: 427 (not E. makasarica Chen, 1993 = E. hirsuta McArdle, 1900 ).

TYPE MATERIAL. — Holotype: cl 13.8 mm, cw 14.5 mm, MUSORSTOM 8, stn CP 1124 ( MNHN- B 27505); paratypes: other six specimens from MUSORSTOM 8 ( Vanuatu) listed under Material examined.

TYPE LOCALITY. — Vanuatu, north of Espiritu Santo island, 15°01.72’S, 166°56.51’E, 532- 599 m.

MATERIAL EXAMINED. — Philippine Islands. South China Sea, MUSORSTOM 2, stn CP 36, 13°31’N, 121°24’E, 569-595 m, 24.XI.1980, 1 ( MNHN-B 18173). — Stn CP 49, 13°38’N, 121°43’E, 416- 425 m, 26.XI. 1980, 2, 3 ( MNHN-B 18172). — Stn CP 63, 14°31’N, 120°15’E, 215- 230 m, 29.XI.1980, 1 ( MNHN-B 18174).

Mindoro Strait. MUSORSTOM 3, stn CP 125, 11°57’N, 121°28’E, 388-404 m, 4.VI.1985, 3, 1 ( MNHN-B 18879).

Bohol. Balicasag island, off Panglao island, tangle nets from local fishermen, XII.2000, 1 (ZRC 2001.0388).

Indonesia. Tanimbar Islands, KARUBAR, stn CP 79, 09°16’S, 131°22’E, 250- 239 m, 3.XI.1991, 1, 1 ovig. ( MNHN-B 22880).

Vanuatu. MUSORSTOM 8, stn CP 991, 18°51.26’S, 168°52. 19’E, 936- 910 m, 24. IX. 1994, 2

cl 13. 3 mm, cw 14. 2 mm and cl 15. 7 mm, cw 16.9 mm respectively ( MNHN-B 27506). — Stn CP 1124, 15°01.72’S, 166°56.51’E, 532-599 m, 9.X.1994, 1 holotype ( MNHN-B 27505), 3

cl 15.7 mm, cw 16.0 mm, cl 14.0 mm, cw 14.6 mm, and cl 14.5 mm, cw 15.5 mm respectively, 1

cl 17.0 mm, cw 18.2 mm ( MNHN-B 28505).

New Caledonia. BATHUS 1, stn CP 663, 20°58.66’S, 165°38.27’E, 730-780 m, 13.III.1993, 2 juv. cl 13.6 mm, cw 14.4 mm and cl 13.3 mm respectively ( MNHN-B 28502). — BATHUS 2, stn CP 739, 23°03.4’S, 166°59’E, 452-464 m, 13.V.1993, 1 cl 13.9 mm, cw 14.5 mm ( MNHN-B 28503). — BATHUS 4, stn CP 950, 20°31.93’S, 164°56. 11’E, 705-750 m, 10. VIII.1994, 1

cl 14.8 mm, cw 15.6 mm, 1 juv. cl 13.7 mm, cw 14.4 mm ( MNHN-B 28504).

ETYMOLOGY. — From brevis (Latin for short) in reference to a short endostome where the anterior border lies well below the antennular fossae of the basal antennular articles.

DISTRIBUTION. — Philippine Is ( Chen 1985, as Ethusa sexdentata ( Stimpson, 1858)) , Indonesia (Tanimbar Is) ( Chen 1997, as E. sexdentata ), Vanuatu ( Chen 2000, as E. makasarica Chen, 1993 ), and now from New Caledonia. Although Chen & Sun (2002: fig. 100) used the illustration of E. abbreviata n. sp. from Chen (1985: figs 5, 6, as E. sexdentata ) in their compendium of primitive crabs from China, their text and records from China actually refer to E. sexdentata , not E. abbreviata n. sp. Depth: 215-936 m ( Fig. 34 ).

SIZE. — Maximum size: cl 15.7 mm, cw 16.9 mm ( MNHN-B 27506); cl 17.0 mm, cw 18.2 mm ( MNHN-B 28505).

DESCRIPTION

Carapace ( Fig. 2A ; Chen 1985: fig. 5, as Ethusa sexdentata ( Stimpson, 1858)) slightly broader than long, particularly females; dorsal surface smooth in larger individuals, short setae in small- er ones; long hairs along anterior, anterolateral borders. Urogastric, cardiac regions slightly elev a t e d, b o r d e r e d b y w i d e g r o o v e s; c e r v i c a l, branchial grooves indistinct; two distinct, round depressions on protogastric region. Branchial regions slightly inflated along sides.

Anterior border of carapace ( Fig. 2A ; Chen 1985: fig. 5, as E. sexdentata ) with slender to broad, nearly triangular, distally acute, straight outer orbital teeth, reaching or nearly reaching shorter frontal teeth. Frontal teeth nearly triangular, equal or nearly-equal. Orbital sinuses broad, U-shaped, nearly symmetrical (inner margins nearly straight, outer margins J-shaped) or symmetrical; lateral frontal sinuses U-shaped; median frontal sinus V-shaped, as wide as lateral frontal sinuses but narrower than orbital sinuses.

Anterior border of endostome ( Fig. 2B ; Chen 1985: fig. 6a, as E. sexdentata ) lies below posteri- or border of antennular fossae of basal antennular articles.

Male chelipeds (P1) smooth ( Chen 1985: fig. 6b, c, as E. sexdentata ), unequal in holotype, equal in other specimens ; larger cheliped of holotype with swollen propodi, 1.7 times fingers; fingers with broad cutting edges; smaller chelipeds (holotype) with slender propodi, 0.7-0.9 times fingers; fingers very slender, long, with broadly round teeth or cutting edges. Female chelipeds similar to smallest male cheliped.

P2, P3 relatively short, very thick; meri with small granules; length of P2 meri 0.8-1.0 times cl, P2 meri 3.8-4.6 times longer than broad. P4, P5 with few short hairs on dactyli, propodi; P5 dactyli thick, curved.

Male abdomen ( Chen 1985: fig. 6d, as E. sexdentata ) with four somites (3-5 fused, basal half swollen), triangular telson. Somite 1 length 2.3 times as broad, somite 6 square, slight swelling at each outer corner of distal margin. Female abdomen ( Chen 1985: fig. 6e, as E. sexdentata ) with six somites, triangular telson; somite 4 broadest, somite 6 longest.

G1 ( Fig. 2C ; Chen 1985: fig. 6f, g, i, as E. sexdentata ) slender; each distal end slightly broad and pointed, short spines along dorsal margin; G2 ( Fig. 2D ; Chen 1985: fig. 6h, as E. sexdentata ) slender, thin, each distal part narrower, point- ed tip.

REMARKS

Ethusa abbreviata n. sp. is very close to Ethusa hirsuta McArdle, 1900 , in the shape of the anteri- or border of the carapace, most particularly in the nearly triangular but relatively slender outer orbital teeth that reach nearly as high as the frontal teeth. Ethusa abbreviata n. sp. can be distinguished from E. hirsuta by having narrower (nearly U-shaped), symmetrical orbital sinuses ( Fig. 2A ) whereas they are wide, V-shaped and asymmetrical in E. hirsuta ( Chen 1993: fig. 9a, as Ethusa makasarica Chen, 1993 , a junior subjective synonym of E. hirsuta McArdle, 1900 ). The most significant difference is that the anterior border of the endostome of the new species extends far below the antennular fossae of the basal antennular articles ( Fig. 2B ). It extends above the level of the antennular fossae in E. hirsuta . Another difference is that the meri of P2 and P3 are clearly thicker and shorter in the new species than in E. hirsuta . There are also some slight differences in the G1, which are of similar shape in both species but in E. abbreviata n. sp. the distal ends have more numerous and abundant spines ( Fig. 2C ) than those of E. hirsuta ( Chen 1993: fig. 9g, h, as E. makasarica ).

There are also close similarities with Ethusa sexdentata ( Stimpson, 1858) , another large-size species. Both species share a similar shape of carapace (smooth dorsal surface with hairs restricted to the anterior border in the largest specimens), relatively short and thick pereopods, and short anterior border of the endostome. In fact, specimens from the Philippines ( Chen 1985) and Indonesia ( Chen 1997) were previously identified by Chen as E. sexdentata . Ethusa abbreviata n. sp. can be easily distinguished from E. sexdentata , however, by its slender outer orbital teeth (wider at the base in E. sexdentata ) and broader, U-shaped, symmetrical or nearly symmetrical orbital sinuses (V-shaped and asymmetrical, the outer margins of the sinuses being conspicuously swollen, in E. sexdentata ; Sakai 1937: fig. 1a; 1976: fig. 26a; Chen 1986: fig. 8-36). The posterior portion of the carapace is slightly wider in E. sexdentata , giving it a rounded appearance ( Sakai 1976: pl. 23, fig. 1; 1965: pl. 11, fig. 2; Miyake 1983: pl. 6, fig. 5). The anterior border of the endostome is shorter in E. abbreviata n. sp. ( Fig. 2B ; Chen 1985: fig. 6a, as E. sexdentata ) than in E. sexdentata ( Ikeda 1998: pl. 16, fig. 6).

There are also similarities with Ethusa indica Alcock, 1894 , particularly in specimens of E. indica where the outer orbital teeth are not as slender and outwardly directed as in typical specimens. Ethusa indica , however, has noticeably longer and more slender P2 and P3 ( Fig. 33C ). Specimens may also be confused with Ethusa orientalis Miers, 1886 , because of the general shape of the carapace and relatively large size ( Fig. 14A ). In contrast to E. abbreviata n. sp., however, E. orientalis has broader, strongly triangular outer orbital teeth, a granular carapace, and a slightly longer anterior border of the endostome.

Figures

FIG. 2. — Ethusa abbreviata n. sp., holotype cl 13.8 mm, cw 14.5 mm, Vanuatu, N of Espiritu Santo, MUSORSTOM 8, stn CP 1124, 532-599 m (MNHN-B 27505); A, dorsal surface of carapace; B, ventral view of anterior portion of body; C, left G1, dorsal views; D, left G2, dorsal view. Scale bars: A, 5 mm; B-D, 2 mm.

FIG. 34. — Bathymetric distribution of Indo-West Pacific ethusine crabs.

FIG. 33. — A, Ethusa granulosa Ihle, 1916, cl 14.7 mm, cw 14.6 mm, Vanuatu, west coast of Malekula, MUSORSTOM 8, stn DW 1061, 458-512 m (MNHN-B 28698) (photograph by J.-L. Menou, IRD, Nouméa); B, Ethusa hawaiiensis Rathbun, 1906, cl 6.7 mm, cw 6.2 mm, Vanuatu, S of Anatom, MUSORSTOM 8, stn CP 963, 400-440 m (MNHN-B 28538) (photograph by J.-L. Menou, IRD, Nouméa); C, Ethusa indica Alcock, 1894, cl 7.8 mm, cw 7.8 mm, Vanuatu, SE of Éfaté, MUSORSTOM 8, stn CP 1036, 920-950 m (MNHN-B 28560) (photograph by J.-L. Menou, IRD, Nouméa); D, Ethusina challengeri (Miers, 1886), cl 25.9 mm, Mid-Indian Basin, SAFARI 2, stn 35, trawl CP 29, 4950-4928 m (MNHN-B 28697) (photograph by P. Briand, IFREMER); E, Ethusina macrospina Ng & Ho, 2003, cl 10.4 mm, cw 11.0 mm, Taiwan, off southwest coast, TAIWAN 2003, stn CD 203, 635-868 m (NTOU) (photograph by T.-Y. Chan, NTOU).

FIG. 14. — Ethusa orientalis Miers, 1886, lectotype cl 15.7 mm, cw 15.1 mm, Fiji, E of Kadavu, Challenger, stn 173A, 567 m (BMNH 84-44); A, dorsal surface of carapace; B, left G1, ventral (left) and dorsal (right) views; C, right G2, dorsal view. Scale bars: A, 3 mm; B, C, 2 mm.