Ethusina robusta (Miers, 1886)

(Fig. 1D, 3D–E)

Ethusa (Ethusina) gracilipes var. robusta MierS, 1886: xxvii, 333, pl. 29 fig. 2 [TYpe lOcaliTY: Arafura Sea, INdONeSia, bY lecTOTYpe deSigNaTiON; CaSTrO 2005].

Ethusa (Ethusina) investigatoris AlcOck, 1896: 285 [TYpe lOcaliTieS: BaY Of BeNgal aNd Laccadive Sea].

Ethusina alcocki Ng & HO, 2003: 74, figS 4, 5 [TYpe lOcaliTY: Off SOuTHerN TaiWaN].

Ethusina robusta.—CaSTrO 2005: 570–575, figS. 22, 25.

Ethusa Sp. MOV 5007.—POOre et al. 2008: 45 (parT).

Material examined. AUSTRALIA: Queensland: QM w14203, 1 male (cl 7.8 mm, cw 6.9 mm), Coral Sea, E of

Cape York, 10°29.21'S, 144°49.23'E, 1503–1520 m, CIDARIS III Expedition, stn 5-1, beam trawl, M. Pichon, A. Birtles, P. Arnold, 10 February 1992; NMV J72891, 1 female (cl 9.7 mm, cw 9.8 mm), E of Gladstone, 23°35.22– 37.02'S, 154°11.64–11.68'E, 1013–1093 m, IN2017_ V03 _121_133, 13 June 2017; NMV J72889, 1 juvenile male (cl 7.4 mm, cw 6.4 mm), 1 ovigerous female (cl 8.6 mm, cw 8.2 mm), 2 females (cl 8.5 mm, cw 7.5 mm; cl 8.7 mm, cw 7.8 mm), E of Gladstone, 23°35.22–37.02'S, 154°11.64–11.68'E, 1013–1093 m, IN2017_ V03 _121_132, 13 June 2017; NMV J72892, 1 juvenile male (cl 6.9 mm, cw 6.0 mm), E of Burleigh Heads, 28°03.27–05.82'S, 154°04.98–04.86'E, 999–1013 m, IN2017_ V03 _100_134, 9 June 2017.

New South Wales: NMV J72887, 1 female (cl 11.2 mm, cw 11.0 mm), E of woolgoolga, 30°05.94–07.68'S, 153°34.36–35.76'E, 1194–1257 m, IN2017_ V03 _080 -176, 5 June 2017.

Western Australia: NMV J58739, 2 females (cl 7.0 mm, cw 5.6 mm; cl 7.7 mm, cw 5.5 mm), N of North west Cape, Barrow L 1 transect, 20°57.15–57.56'S, 114°00.78–00.56'E, 1000 m, SS05/07/002, coll. M. Gomon, 9 June 2007; NMV J55605, 1 female (cl 8.4 mm, cw 7.2 mm), off Two Rocks, 31°43.458–43.104'S, 115°14.640– 14.466'E, 102 m, beam trawl, SS10/05/002, coll. R. wilson, 19 November 2005; NMV J53952, 1 juvenile male (cl 6.5 mm, cw 5.6 mm), Perth Canyon, 31°58.283–57.317'S, 115°06.000–06.833'E, 848–1050 m, SS10/05/071, beam trawl, coll. R. wilson, 29 November 2005.

Remarks. The present specimens constitute the first records of E. robusta from Australia and conform well to recent published accounts of the species (i.e., Ho & Ng 2003, as E. alcocki; Castro 2005). The western Australian material was among specimens listed by Poore et al. (2008) as “ Ethusa sp. MoV 5007” (Fig. 3E). In the present series, the length:height proportions of the pereopod 2 merus occupy a similar range in both sexes: 8.4–11.5 (males) and 8.4–11.0 (females) and largely correspond to ratios reported by Castro (2005). Apparently, the chelipeds and walking legs of E. robusta are more brightly pigmented in juveniles than adults (Figs. 3D, E). The males (Fig. 3D), all small, usually have proportionally shorter, less divergent outer orbital teeth than other specimens (Fig. 3E), approaching that figured by Alcock & MacGilchrist (1905: pl. 72 fig. 3, 3a) for a male syntype of E. investigatoris. In one male (QM w14203, cl 7.8 mm; Fig. 1D), the pereopod 2 merus is proportionally stouter than in other males (length:height 8.4 versus 10.1–11.5) and the cornea extends laterally to, but not beyond, the lateral margin of the outer orbital spine—these differences are probably a function of individual variation and small body size.

Distribution. western India to Indonesia, the Solomon Islands, New Caledonia, Vanuatu, Taiwan and Fiji; now also from Australia; 102–2624 m (usually> 800 m) (Castro 2005).