Ethusa izuensis Sakai, 1937

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 : 530-532

Ethusa izuensis Sakai, 1937

Ethusa izuensis Sakai, 1937: 77 (key), 80, figs 1d, 4; 1956: 7 (list), fig. 8.4; 1965: 23, pl. 12, figs 1, 2 (colour); 1976: 66, figs 26, 29. — Serène 1968: 40 (list). — Takeda & Miyake 1972: 67. — Serène & Lohavanijaya 1973: 35 (key). — Serène & Vadon 1981: 118-121. — Miyake 1983: 18, 199, pl. 6, fig. 6 (colour). — Chen 1985: 193, figs 11, 12, pl. 1, fig. 2; 1986: 131, fig. 12(59-61); 1993: 318 (key), 324; 1998: 233, fig. 4; 2000: 427. — Dai et al. 1986: 52, fig. 27(5-6), pl. 6, fig. 5. — Dai & Yang 1991: 60, fig. 27(5-6), pl. 6, fig. 5. — Nagai 1995: 60, pl. 1, fig. 8. — Muraoka 1998: 17. — Takeda 2001: 225, 254, 259. — Chen & Sun 2002: 54, 243, fig. 103, pl. 9, fig. 6. — Marumura & Kosaka 2003: 23.

TYPE MATERIAL. — Holotype:, Japan, Honshu , Sagami Bay, between Ito and Hatsu Shima, Misago, VI.1934. Deposit unknown.

As noted by Chen (1985: 194), the holotype was listed as a female in the description ( Sakai 1937: 81) but as a male in the caption of a figure in a later publication ( Sakai 1976: fig. 29). The holotype was probably a female because of its large size (cl 11.5 mm, cw 10.4 mm).

TYPE LOCALITY. — Japan, Honshu, Sagami Bay, between Ito and Hatsu Shima.

MATERIAL EXAMINED. — Japan. Honshu, Tateyama Bay, Boso Peninsula, 35°00.57’N, 139°41.45’E, 100- 258 m, T. Komai coll., 17.VIII.1999, 1, 1 ( CBM-ZC 4705). — Sagami Bay, Amadaiba Bank, T. Sakai and Emperor Hirohito coll., 150-250 m, 17.XII.1958, 2 ( SMF 28926). — Sagami Bay, Hatsu Shima, 30.I.1960, 1 ( SMF 28927).

Taiwan. TAIWAN 2002, stn CP 162, 22°09.6’N, 120°37.9’E, 190-200 m, 25.V.2002, 2 ( NTOU).

Philippine Islands. South China Sea, MUSORSTOM 1, stn CP 24, 14°00 ’N, 120°18.0’E, 189-209 m, 22.III.1976, 1 ( MNHN-B 18906). — Stn CP 25, 14°02.7’N, 120°20.3’E, 200- 191 m, 22.III.1976, 2 ( MNHN-B 18910). — Stn CP 30, 14°01.3’N, 120°18.7’E, 186- 177 m, 22.III.1976, 1 ( MNHN-B 18912). — Stn CP 32, 14°02.2’N, 120°17.7’E, 193- 184 m, 23.III.1976, 1 ( MNHN-B 18911). — Stn CP 34, 14°01.0’N, 120°15. 8’E, 191- 188 m, 23.III.1976, 1 ( MNHN-B 18905). — Stn CP 36, 14°01.2’N, 120°20.2’E, 210- 187 m, 23.III.1976, 1 ( MNHN-B 18904). — Stn CP 57, 13°53.1’N, 120°13.2’E, 107- 96 m, 26.III.1976, 1 ( MNHN-B 18901). — Stn CP 64, 14°00.5’N, 120°16.3’E, 194- 195 m, 27.III.1976, 1 juv. ( MNHN-B 18900).

MUSORSTOM 2, stn CP 2, 14°01’N, 120°17’E, 184-186 m, 20.XI.1980, 1 ( MNHN-B 18907). — Stn CP 18, 14°00’N, 120°18 ’E, 188-195 m, 22.XI.1980, 1 ( MNHN-B 18909), 1 ( MNHN- B 18903). — Stn CP 51, 14°00’N, 120°17’E, 170- 187 m, 27.XI.1980, 2, 2 ( MNHN-B 18928). — Stn CP 64, 14°01’N, 120°19’E, 191- 195 m, 29.XI.1980, 1 juv. ( MNHN-B 18908). — Stn CP 66, 14°00’N, 120°20 ’E, 192-209 m, 29.XI.1980, 1 ( MNHN-B 18898).

MUSORSTOM 3, stn CP 87, 14°00.6’N, 120°19.6’E, 191-197 m, 31.V.1985, 1, 1 ( MNHN-B 28584). — Stn CP 88, 14°01’N, 120°17 ’E, 183-187 m, 31.V.1985, 1, 1 ( MNHN-B 18893). — Stn CP 91, 14°00’N, 120°18’E, 190-203 m, 31.V.1985, 1 ( MNHN-B 18894). — Stn CP 92, 14°03’N, 120°12’E, 224 m, 31.V.1985, 2, 1 ( MNHN-B 18895). — Stn CP 108, 14°01’N, 120°18’E, 188-195 m, 2.VI.1985, 1 ( MNHN-B 18896). — Stn CP 109, 14°00’N, 120°18’E, 190-198 m, 2.VI.1985, 2, 1 ( MNHN-B 18892). — Stn CP 111, 14°00’N, 120°18’E, 193-205 m, 2.VI.1985, 1 ( MNHN-B 18897).

Verde Island Passage, MUSORSTOM 2, stn CP 35, 13°28’N, 121°12’E, 160-198 m, 24.XI.1980, 1 ( MNHN-B 18902).

Visayan Sea, MUSORSTOM 3, stn CP 143, 11°29’N, 124°11’E, 205-214 m, 7.VI.1985, 1 ( MNHN-B 18899 ). Bohol, Balicasag island, off Panglao island , tangle nets from local fishermen, XII.2000, 1 ( ZRC 2001 .0388), 1 ( ZRC 2001 .0390) ; 50-500 m, 28.XI.2001, 6, 4 ( ZRC 2001.0517 ) ; local shell fishermen, 200-300 m, VI.2002, 3 ( ZRC 2002 .0643), 2 ( ZRC 2002 .0644), 1 ( ZRC 2002.0645 ) ; purchased from fishermen, P. K. L. Ng et al., 25-30.VII.2003, 2, 3 ( ZRC 2003.0297 ) .

Solomon Islands. SALOMON 1, stn CP 1837, 10°12.8’S, 161°28.6’E, 381-383 m, 5.X.2001, 1 ( MNHN-B 28593).

Vanuatu. MUSORSTOM 8, stn DW 1060, 16°13.82’S, 167°20.80’E, 397- 375 m, 2.X.1994, 1 juv. ( MNHN-B 27503).

New Caledonia. ORSTOM trawling, 22°40’- 22°50’S, 167°10’- 167°30’E, 200-350 m, 10.X.1986, 2 ( MNHN-B 19095).

BATHUS 1, stn CP 712, 21°44.26’S, 166°35.34’E, 210 m, 19.III.1993, 1 ( MNHN-B 28589).

BATHUS 2, stn DW 714, 22°37.79’S, 167°09.71’E, 124 m, 10.V.1993, 1 juv. ( MNHN-B 28586). — Stn DW 732, 22°49.76’S, 166°45.12’E, 236-264 m, 13.V.1993, 1 ( MNHN-B 28583).

BATHUS 3, stn DW 836, 22°02’S, 166°59’E, 295- 306 m, 30.XI.1993, 1 ( MNHN-B 28587).

HALIPRO 1, stn CP 851, 21°43’S, 166°37’E, 314- 364 m, 19.III.1994, 3 ( MNHN-B 28588).

BATHUS 4, stn DW 904, 18°59.85’S, 163°11.76’E, 461 m, 4.VIII.1994, 1, 1 ovig. ( MNHN-B 28590).

Loyalty Islands. LIFOU 2000, stn DW 1650, 20°54.15’S, 167°01.7’E, 120-250 m, 15/18/ 20.XI.2000, 1 ( MNHN-B 28591).

Fiji. MUSORSTOM 10, stn CP 1323, 17°16.1’S, 177°45.7’E, 143-173 m, 7.VIII.1998, 1 ( MNHN- B 28595). — Stn CP 1348, 17°30.3’S, 178°39.6’E, 353-390 m, 11.VIII.1998, 1 ( MNHN-B 28596). — Stn CP 1357, 17°48.5’S, 178°46.7’E, 81-110 m, 13.VIII.1998, 1 ( MNHN-B 28597). — Stn CP 1363, 18°12.4’S, 178°33.0’E, 144-150 m, 15.VIII.1998, 1, 1 ( MNHN-B 28598). — Stn CP 1366, 18°12.4’S, 178°33. 1’E, 149-168 m, 15.VIII.1998, 1 ( MNHN-B 28599). — Stn CP 1385, 18°18.5’S, 178°05.2’E, 227-284 m, 18.VIII.1998, 1 ( MNHN-B 26600). — Stn CP 1387, 18°18.5’S, 178°04.7’E, 229-370 m, 19.VIII.1998, 1, 1 ( MNHN-B 26601). — Stn CP 1389, 18°18.6’S, 178°04. 7’E, 241-417 m, 19.VIII.1998, 1 ( MNHN-B 2602). — Stn CP 1390, 18°18.6’S, 178°05.7’E, 234-361 m, 19.VIII.1998, 2 ( MNHN-B 2603).

BORDAU 1, stn CP 1412, 16°06’S, 179°28’W, 400- 407 m, 26.II.1999, 1 ( MNHN-B 28604). — Stn CP 1421, 17°08’S, 178°59’W, 403-406 m, 28.II.1999, 1 ( MNHN-B 28605). — Stn CP 1423, 17°08’S, 178°59’W, 402-410 m, 28.II.1999, 1 ( MNHN-B 28606). — Stn CP 1450, 16°44’S, 179°58’W, 327- 420 m, 4.III.1999, 1 juv. ( MNHN-B 28607). — Stn CP 1465, 18°09’S, 178°39 ’W, 290-300 m, 6.III.1999, 1 ( MNHN-B 28608). — Stn CP 1476, 19°41’S, 178°11’W, 310-420 m, 8.III.1999, 1 juv.

( MNHN-B 28609). — Stn CP 1478, 20°59’S, 178°44’W, 386-396 m, 9.III.1999, 1 juv. ( MNHN- B 28610). — Stn CP 1500, 18°42’S, 178°26’W, 366- 389 m, 12.III.1999, 2 ( MNHN-B 28611). — Stn CP 1506, 18°09’S, 178°37’W, 294-300 m, 13.III.1999, 2 ( MNHN-B 28612).

Tonga. BORDAU 2, stn CP 1511, 21°08’S, 175°22’W, 384-402 m, 31.V.2000, 1 ( MNHN-B 28594). — Stn CP 1541, 21°15’S, 175°14’W, 319- 333 m, 5.VI.2000, 1 ( MNHN-B 28643). — Stn CP 1567, 21°02’S, 175°19’W, 351-356 m, 10.VI.2000, 1 juv., 1, 1 ( MNHN-B 28592).

DISTRIBUTION. — Southern Japan (see Sakai 1976), East China Sea ( Takeda & Miyake 1972), South China Sea ( Chen 1986), Philippine Is ( Chen 1985, 1993), Indonesia (Makassar Strait) ( Chen 1993), Vanuatu ( Chen 2000), New Caledonia ( Chen 1993), and now from Taiwan, Solomon Is, Loyalty Is, Fiji, and Tonga. An earlier record from Taiwan ( Fang 1991) is questioned by Ng et al. (2001). Depth: 30 ( Sakai 1937) - 600 m ( Fig. 34 ).

SIZE. — Maximum size: cl 10.8 mm, cw 10.5 mm ( ZRC 2001.0517), cl 15.0 mm, cw 15.4 mm ( ZRC 2001.0517).

REMARKS

There is considerable variation in the characters that are used in part to define Ethusa izuensis . The outer orbital teeth vary from triangular and symmetrical to proximally broad. The density of hair also varies, even in material collected from the same location. In fresh material, a considerable amount of sediment may be trapped in the hairs. Morphological variation did not follow any defined geographical patterns that would suggest a cline or even separate species.

Ethusa izuensis may be confused with E. minuta Sakai, 1937 . Both species have slender and point- ed outer orbital teeth but the teeth are more slen- der and are directed slightly more outwardly in E. minuta ( Sakai 1937: fig. 1e; 1965: pl. 11, fig. 2; 1976: fig. 26e; Chen 1986: fig. 12.55; 1993: fig. 10a; Chen & Sun 2002: fig. 104.1) than in E. izuensis ( Sakai 1937: fig. 1d; 1976: fig. 26d; Chen 1985: fig. 11; 1986: fig. 12.59; Chen & Sun 2002: fig. 103.1). A male illustrated by Sakai (1965: pl. 12, fig. 1) is debatably assigned to E. izuensis . It has slender outer orbital teeth, with the left one clearly directed outwardly. The sides of the carapace are only slightly broader on the posterior half in E. izuensis ( Sakai 1965: pl. 12, figs 1, 2; 1976: 29; Miyake 1983: pl. 6, fig. 6; Chen 1985: fig. 11; 1986: fig. 12.59; Chen & Sun 2002: fig. 103.1), whereas there is a conspicuous constriction at the level of the branchial groove in E. minuta ( Sakai 1965: pl. 11, fig. 2; 1976: pl. 23, fig. 4; Chen 1986: fig. 12.55; 1993: fig. 10a; Chen & Sun 2002: fig. 104.1). The orbital sinuses are only slightly wider or about the same width as the frontal sinuses in E. izuensis while they are much wider in E. minuta ( Sakai 1937: fig. 1; 1976: fig. 26). The anterior border of the endostome extends only to the anterior margin of the antennular fossae of the basal antennular articles in E. izuensis ( Chen 1985: fig. 12a; Chen & Sun 2002: fig. 103.2) but in E. minuta it extends beyond the antennular fossae in such a way that it reaches the ventral fold of the median central sinus, a character pointed out by Sakai (1937: 77, 82; 1976: 63). Each G1 has a pointed tip and is more slender and longer in E. izuensis ( Chen 1985: fig. 12f, h; 1986: fig. 12.61; Chen & Sun 2002: fig. 103.7) than in E. minuta ( Chen 1986: fig. 12.57; 1993: fig. 10f; Dai & Yang 1991: fig. 27.2; Chen & Sun 2002: fig. 104.6). The maximum size reached by adults is bigger in E. izuensis than in E. minuta . The dorsal surface of the carapace of E. izuensis is covered in varying amounts of hair whereas the dorsal surface (except the anterior and anterolateral borders) of E. minuta lacks any conspicuous hair, although conspicuous plumose setae are often found along the lateral and posterior borders of the carapace and on the pereopods. The cheliped meri are devoid of conspicuous setae in E. izuensis , whereas there are usually setae on the cheliped meri of E. minuta ( Chen 1986: fig. 12.56).

Ethusa izuensis is found at greater depths than E. minuta . All specimens of E. izuensis studied during this investigation, from Japan to Tonga, were collected at depths greater than 100 m whereas the opposite is the case for E. minuta . Nevertheless, Sakai (1937: 81, 1976: 66) record- ed E. izuensis at depths of 30-100 m in Japan.

Ethusa izuensis is also similar to E. foresti Chen, 1985 . Differences between the two species are outlined in the discussion of E. foresti (see above).

Figures

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