Austinograea alayseae Guinot, 1990

Austinograea alayseae Guinot, 1990 View in CoL

Austinograea alayseae Guinot, 1990: 880 View in CoL , 898, figs 1-3, pl. 1 figs A-F. — Guinot & Segonzac 2018: 75, 79, 76, 78, 96 (key), 99, 100, 101. — Tsuchida & Fujikura 2000: 407, 413. — Tsuchida & Hashimoto 2002: 643, 646, 647, 649 (key), figs 5, 6, 8. — Kim et al. 2013: 1, 2, 5-9, fig. 2, tables 1-3. — Lee et al. 2019b: 2, 3, 6-11, figs 1-3, tables 2, 3-5, S1.

MATERIAL EXAMINED. — SW Pacific • 1 young ♀, without chelae; Manus Basin, PL 733 - PBT7 ; SnowCap / Big papi; 3°43.263’S, 151°40.485’E; 1669 m; 19.V.2019; CHU-512; MNHN-IU-2024-6027 GoogleMaps • 1 very small ♀ with one chelae; Manus Basin, Pacmanus ; PL734 - ASPI3 ; 3°43.040’S, 151°40.375’E; 1769 m; 19.V.2019; MNHN-IU-2024-6081 GoogleMaps • 1 ♀ 16.3 × 24.6 mm, native right-handed; Manus Basin; PL736 - Aspi 7, North Su / Solwara 1; 3° 47.957’S, 152°6.090’E; 1195 m; 23.V.2019; CHU-510; Hourdez det. Austinograea ; MNHN-IU-2024-6024 GoogleMaps • 4 ♀: 1 ♀ 33.9 × 53.2 mm, left-handed, CHU-660; 1 ♀ 30,6 × 48.3 mm, with two cutters, the left being bigger, CHU-661, 1 ♀ 28.5 × 35 mm, with two cutters, the left being bigger, 1 ♀ 28.8 × 45.4 mm, native right-handed; PL736 – GBT3 , North Su / Solwara 1, PL736 - GBT3 ; 3°47.942’S, 152°6.060’E; 1210 m; 22.V.2019; Hourdez det. Austinograea sp. , CHU-662; MNHN-IU-2024-6028 GoogleMaps • 1 ♀ 35.5 × 57.7 mm, left-handed; Manus Basin; PL736 - GBT4 , North Su / Solwara 1; 3°47.957’S, 152°6.090’E; 1195 m; 23.V.2019, Hourdez det. Austinograea ; CHU-509; MNHN-IU-2024-6030 GoogleMaps • 1 ♂ 9.7 × 14.2 mm, right-handed; Manus Basin ; PL734 - GBT4 ; 3°43.649’S, 151°40.866’E; 1725 m; 19.V.2019; Roman’s Ruins / Solwara 6, 7 and 8; Hourdez det. Austinograea ; CHU-513; MNHN-IU-2024-6025 GoogleMaps • 1 ♀ 12.0 × 18.0 mm, native right-handed; same data as for preceding; Hourdez det. Austinograea , CHU-514 MNHN-IU-2024-6029 GoogleMaps • 1 ♀ 26.2 × 41.2 mm, native right-handed; Manus Basin; PL737 - Panier, South Su , Pacmanus area ; 3°48.565’S, 152°6.314’E; 1330 m; 24.V.2019; Hourdez det. Austinograea sp. ; MNHN-IU-2024-6031 GoogleMaps .

OTHER MATERIAL. — We add one specimen collected in high temperature vent site by the BAMBUS cruise in 2011 (see participants in Bach et al. 2011), and sent to the MNHN in 2011 (see Bach et al. 2011).

SW Pacific • 1 ♂ 12.9 × 20.5 mm, left-handed; Manus Basin, site Pacmanus, R/V Sonne ; ROV QUEST; BAMBUS cruise; éch. 49 ROV 5, site Solwara 8/Fenway; 03°43.72’S, 151°40.33’E; 1716 m; 9.VII.2011; W. Bach coll., ex-Bremen University collection, M. Segonzac det? A. alayseae, XII.2011 (but not studied further MNHN-IU-2024-6068). GoogleMaps

REMARKS

Austinograea alayseae View in CoL , originally collected in the Lau Back-Arc Basin, west of the Tonga Islands, along the Valu Fa Ridge, at around 176°38’W and between 22°34’S and 22°10’S, at 1750 m depth ( Guinot 1990) and already found in the Eastern Lau Spreading Center ( Corbera & Segonzac 2010; Podowski et al. 2010; Sen et al. 2013, 2014, 2016) ( Fig. 1 View FIG ), is distributed over a wide geographical range. It has been reported from the North Fiji Basin ( Jollivet et al. 1989, as bythograeid sp.; Guinot 1997 in Desbruyères & Segonzac 1997; Galkin 1997; Hashimoto et al. 1999, as bythograeid sp.; Guinot & Segonzac 2006 a; Desbruyères et al. 2006; Shields & Segonzac 2007), and from the Tonga Arc and Manus Basin ( Lee et al. 2019b). It has been reported from both active and inactive sites (Kowalczyk and Binns sites, respectively) ( Erickson et al. 2009).

All the Austinograea alayseae View in CoL material from the CHUBACARC 2019 cruise studied here was collected in abundance in the Manus Basin, and more precisely in the Pacmanus area. Scavenger and carnivore, abundant at vent openings, crawling actively on snail thickets, this species dominates the Manus Basin fauna ( Galkin 1992, 1997: fig. 1; Tsuchida & Hashimoto 2002; López-González et al. 2005; Guinot & Segonzac 2006; Lee et al. 2019b: table 2). Females of A. alayseae View in CoL are much more numerous and reach a much larger size than males: the maximum size of males in the material from the CHUBACARC 2019 cruise is 14.2 mm carapace wide, that of females is 57.7 mm wide. In the material from the Vai Lili Site of Lau Basin studied by Guinot (1990: 899), the largest male measured 51.3 mm carapace wide, and the largest female 63 mm.

According to Chabert (2021: 11, 26, 32, table 2), phylogenetic analysis, which allowed her to define the delimitation of nine bythograeoid species in the Woodlark Basin, has demonstrated the presence within the morpho-species Austinograea alayseae of at least three cryptic species, each with different distributions. Her study recognised in the Woodlark Basin: two specimens of ‘ A. alayseae A’ (also present in the North Fiji and Lau Basins, and the Futuna Volcanic Arc), five specimens of ‘Gen. sp. B’ (apparently endemic to the La Scala vent Field), one specimen of the ‘Gen. sp. C’, and one specimen of ‘ A. aff. hourdezi ’. Unfortunately, from the material analysed by Chabert (2021: table 2, p. 15), we received only the one that identified as ‘ A. alayseae A’. As, we did not obtain the material identified as ‘ A. alayseae B, C and D’, in this article we will leave aside the interpretation of these results.

In the Manus Basin, Chabert (2021: 27, 32, table 2) did not report a ‘Gen. sp. B’ but recognised seven ‘ Austinograea alayseae B’ there, which were not located in any other basin, and one specimen of A. aff. williamsi , which she also found, with two specimens, in the Lau Basin. The material in our hands, however, does not allow us to relate these various Austinograea to any known species.