Ethusina castro Ahyong, 2008

Ahyong, Shane T. & Farrelly, Caroline A., 2018, First Australian records of Ethusina (Crustacea: Decapoda: Ethusidae) and additional records from New Zealand, Zootaxa 4486 (2), pp. 161-168 : 162-164

publication ID	https://doi.org/ 10.11646/zootaxa.4486.2.5
publication LSID	lsid:zoobank.org:pub:7CE9F0D2-EF87-45DE-BE7C-73BC79BCA7F6
DOI	https://doi.org/10.5281/zenodo.5969752
persistent identifier	https://treatment.plazi.org/id/03C187C8-FF8D-512A-FF52-FEBDFD212665
treatment provided by	Plazi
scientific name	Ethusina castro Ahyong, 2008
status

Treatment

Ethusina castro Ahyong, 2008 View in CoL

( Figs. 1A View FIGURE 1 , 2 View FIGURE 2 , 3A, B View FIGURE 3 )

Ethusina castro AHYONg, 2008 View in CoL : 26–29, figS 12A, 13A–B, 14A–E, 28A–B [WHakaTaNe SeamOuNT, BaY Of PleNTY, NeW ZealaNd].—Webber et al. 2010: 226.—YaldWYN & Webber 2011: 230.—Lörz et al. 2012: 47.

Material examined. AUSTRALIA: Queensland: NMV J72901 View Materials , 1 male (cl 8.5 mm, cw 7.0 mm), E of Gladstone , 23°37.872–39.540'S, 154°38.628–39.582'E, 1770– 1761 m, IN2017_ V03 _128 -149, 13 June 2017; NMV J72899 View Materials , 1 female (cl 10.6 mm, cw 9.6 mm), E of Fraser Island , 25°19.518–21.078'S, 154°04.098–04.560'E, 2342–2350 m, IN2017_ V03 _115 -114, 11 June 2017; NMV J72494 View Materials , 1 male (cl 12.3 mm, cw 11.0 mm), E of Bribie Island , 26°56.748–58.272'S, 153°56.700–57.072'E, 2520–2576 m, IN2017_ V03 _101 -103, 9 June 2017.

New South Wales: NMV J72905 View Materials , 1 juvenile female (cl 6.9 mm, cw 6.9 mm), E of Byron Bay , 28°40.59– 42.54'S, 154°11.382–12.196'E, 2562–2587 m, IN2017_ V03 _90 -134, 7 June 2017; NMV J72904 View Materials , 1 male (cl 7.4 mm, cw 7.0 mm), E of woolgoolga, 30°05.862–07.158'S, 153°52.47–53.922'E, 2429–2518 m, IN2017_ V03 _086- 149, 5 June 2017; NMV J72914 View Materials , 3 females (cl 9.6 mm, cw 9.0 mm to cl 14.7 mm, cw 14.6 mm), ESE of Seal Rocks , 32°34.500–37.899'S, 153°08.52–09.702'E, 2474–2595 m, IN2017_ V03 _070 -131, 3 June 2017; NMV J72916 View Materials , 1 male (cl 8.7 mm, cw 7.8 mm), ESE of Seal Rocks , 32°34.500–37.899'S, 153°08.52–09.702'E, 2474– 2595 m, IN2017_ V03 _070 -131, 3 June 2017; NMV J72578 View Materials , 1 male (cl 13.2 mm, cw 12.5 mm), E of Newcastle, 32°59.100– 33°00.900'S, 152°54.780–57.120'E, 2704–2902 m, IN2017_ V03 _067 - 109; NMV J72917 View Materials , 1 male (cl 11.9 mm, cw 11.7 mm), E of Ulladulla , 35°19.980–19.920'E, 151°12.840–15.480'E, 2636–2650 m, IN2017_ V03 _056 - 229; NMV J72547 View Materials , 2 males (cl 11.1 mm, cw 10.1 mm; cl 11.7 mm, cw 11.1 mm), 2 females (cl 14.8 mm, cw 15.0 mm; cl 15.0 mm, cw 15.1 mm), E of Bermagui , 36°18.9–21.36'S, 150°38.64–39.06'E, 2687– 2821 m, mud, IN2017_ V03 _044, 27 May 2017 ; AM P 102237, 1 male (cl 12.5 mm, cw 11.1 mm), 1 female (cl 15.8 mm, cw 16.2 mm), E of Bermagui , 36°18.9–21.36'S, 150°38.64–39.06'E, 2821– 2687 m, mud, IN2017_ V03 _044, 27 May 2017 ; NMV J72604 View Materials , 1 female (cl 14.9 mm, cw 14.6 mm), E of Bermagui , 36°18.9–21.36'S, 150°38.64– 39.06'E, 2821– 2687 m, IN2017_ V03 _044, 27 May 2017 .

NEw ZEALAND: NIwA 32187, 1 juvenile female (cl 4.5 mm, cw 4.0 mm), Monowai Caldera, Kermadec Ridge, 25°47.40'S, 177°06.36'w, 640 m, SO192-2/12, RV Sonne, 2 May 2007 GoogleMaps ; NIwA 69442, 1 male (cl 13.5 mm, cw 12.7 mm), Lord Howe Rise, 35°43.69–43.09'E, 160°16.20–12.79'E, 3480–3798 m, NZOI stn U202, Cruise 1137, 28 September 1982; NIwA 82933, 1 female (cl 8.0 mm, 7.1 mm), Clark Seamount, 36°26.718–26.568'S, 177°50.352–50.418'E, 850–927 m, epibenthic sled, TAN1206/99, 24 April 2012; NIwA 82903, 1 juvenile male (cl 6.6 mm, cw 5.5 mm), Clark Seamount, 36°26.718–26.568'S, 177°50.352–50.418'E, 850–927 m, epibenthic sled, TAN1206/99, 24 April 2012.

Remarks. The present series of E. castro includes the first known males ( Fig. 1A View FIGURE 1 , 3B View FIGURE 3 ), enabling documentation of the male gonopods and abdomen ( Fig. 2A–E View FIGURE 2 ). All have the characteristic angular dorsal outline of the submedian frontal lobes as in the holotype ( Fig. 2F View FIGURE 2 ). Male E. castro differ from females ( Ahyong 2008) in sexually dimorphic features such as the less inflated carapace with slightly more protruding front, proportionally larger chelipeds and more elongated walking legs (pereopod 3 1.0–1.1 cl versus almost 0.8 cl in females). Specimens of about 10 mm cl and larger appear to be mature. Juvenile E. castro have more pronounced dorsal granulation and angular frontal teeth than adults, and in the 7–9 mm cl size range, could be mistaken for E. brevidentata Chen, 1993 , a small species from New Caledonia not exceeding 10 mm cl (Castro 2005). Sizematched specimens of the two species can be distinguished by the distinctly more setose G1 of E. castro (sparsely setose in E. brevidentata ; compare Fig. 2A–B View FIGURE 2 , Chen 1993: fig. 16G–I) and subtle abdominal differences. Both abdominal somite 6 and the fused somites 3–5 in males are proportionally slightly more elongate in E. castro than in E. brevidentata (compare Fig. 2E View FIGURE 2 and Chen 1993: fig. 16E). Similarly, small female E. castro have a proportionally narrower abdominal somite 6 than E. brevidentata (compare Ahyong 2008: fig. 14E and Chen 1993: fig. 16F).

The mature male gonopods of E. castro in many respects resemble those of its apparently wide-ranging congener, E. challengeri (Miers, 1886) ( Fig. 2A–D View FIGURE 2 ; Castro 2005: fig. 16C, D). The gonopods are incompletely developed in the juvenile male (cl 6.6 mm, cw 5.5 mm, NIwA 82903), but well developed in other males. The G1 of E. castro has a larger and more angular subdistal flange on the sternal margin of the distal aperture ( Fig. 2A, B View FIGURE 2 ) than in E. challengeri , and the G2 is apically acute rather than blunt and subtruncate ( Fig. 2C, D View FIGURE 2 ). Castro (2005) described and figured the gonopods of E. challengeri from the southwestern Indian Ocean, observing that the G1 was distally rounded with a partial subdistal band of plumose setae, compared to a slightly more angular tip with a complete band of subdistal setae in northwest Pacific material. The G1 apex of E. castro is apparently closer to that of the northwestern Pacific E. challengeri than those from the southwestern Indian Ocean in having only a partial band of subdistal setae.

The walking legs of E. castro are proportionally shorter than in E. challengeri with the pereopod 2 merus of females 0.8 cl or less rather than as long as carapace length. with the pereopod 2 merus of male E. castro at 1.0–1.1 cl, that of male E. challengeri is likely to be longer still. Northwestern Indian Ocean specimens reported by Spiridonov & Türkay (2007) as E. challengeri , however, differ from E. challengeri sensu stricto in frontal carapace ornamentation and having proportionally shorter, stouter, walking legs ( Ahyong 2008); they appear to be neither E. challengeri nor E. castro and probably represent an undescribed species.

The known distribution is extended from the type locality (whakatane Seamount, Bay of Plenty, 2672–2776 m) on the southern Kermadec Ridge, westwards to the Lord Howe Rise and eastern Australian continental slope, and northwards to Monowai Caldera (northern Kermadec Ridge). The bathymetric range is also significantly expanded, with the Monowai Caldera (640 m), and Clark Seamount (927 m) specimens from the shallowest depths; all others were taken at lower bathyal depths (1770–3798 m).

The Monowai Caldera specimen (NIwA 32187) is the first ethusid to be recorded from a volcanically active site. Monowai Caldera is also shared by the hydrothermal vent king crab, Paralomis hirtella Saint Laurent & Macpherson, 1997 (Ahyong 2010) . Other decapods from vent sites on the southern Kermadec Ridge in the Bay of Plenty include: the brachyuran crabs Gandalfus puia McLay, 2007 , and Xenograpsus ngatama McLay, 2007 ; the squat lobster, Munidopsis maunga Schnabel & Bruce, 2006 ; and the caridean shrimps Alvinocaris alexander Ahyong, 2009 , A. niwa webber, 2004, Lebbeus wera Ahyong, 2009 , and Nautilocaris saintlaurentae Komai & Segonzac, 2004 (Ahyong 2009) .

Distribution. Seamounts in the Bay of Plenty, northeastern New Zealand, and now from eastern Australia, the Lord Howe Rise and Monowai Caldera; 640–3798 m.