Kallograea jolliveti ( Guinot & Segonzac, 2018 ), 2025

Guinot, Danièle & Ng, Peter K. L., 2025, Kallograea kulolasi n. gen., n. sp. and K. jolliveti (Guinot & Segonzac, 2018) from the hydrothermal Kulo Lasi Volcano Caldera, West Pacific; and a reappraisal of Austinograea Hessler & Martin, 1989 and Gandalfus McLay, 2007 (Decapoda, Brachyura, Bythograeoidea), Zoosystema 47 (33), pp. 773-797 : 783-795

Kallograea jolliveti ( Guinot & Segonzac, 2018) n. comb.

( Figs 8; 9)

Austinograea jolliveti Guinot & Segonzac, 2018: 89 , figs 9A-H, 10A-E, 11A-E.

MATERIAL EXAMINED. — Holotype. Western Pacific • ♂ 12.8 × 20.0 mm (right-handed); North Fiji Basin; STARMER II cruise, dive 18 ( PL 18 ); Mussel Valley site ; 18°50’S, 173°29’E; 2750 m; 3.VII.1989; MNHN-IU-2016-10769 .

Paratypes. Western Pacific • 1 ♂ (slightly right-handed) 14.7 × 25.4 mm, 1♀ 12.4 × 21.6 mm; same data as for holotype; MNHNIU-2016-10770 .

OTHER MATERIAL. — Western Pacific • 1 ♀ 13.6 × 22.0 mm (left-handed); Lau Back-Arc Basin; MGLN07MV cruise, dive 237; ABE site; 20°45.65’S, 176°11.45’E; 2130 m; 25.IX.2006; MNHNIU-2016-10751 .

NEW MATERIAL. — Western Pacific • 1 ♂ 14.3 × 22.7 mm (slightly left-handed), Futuna 1 cruise, Kulo Lasi, PL1776-4 – aspi 4; 14°56.35’S, 177°15.57W; 1406 m; 12.IX.2010; L. Menot coll.; R/V Atalante ; ROV Nautile; M. Segonzac 06.2011 det. Austinograea sp. ; ZRC 2024.0725 ( MNHN-IU-2009-4045 ) • 2 ♂ 8.0 × 13.4 mm, 9.0 × 12.4 mm, 1 ♀ 8.4 × 13.8 mm (most of legs and chelipeds detached), Futuna 3 cruise , PL06 – aspi 04; MNHN-IU-2024-6075 • 1 ♀ 13.5 × 20.0 mm, CHUBACARC cruise, PL734 - GBT2, Manus Basin, Pac Manus , Roman’s Ruins ; 03°43 649, 151°40 861; 1725 m; MNHN-IU-2024-6026 [CHU 511] • 1 ♂ 12.2 × 16.8 mm (right-handed); CHUBACARC cruise, PL733 - GBT5; Manus Basin, Pac Manus , Fenway ; MNHN-IU-2024-6551 .

REMARKS

See description by Guinot & Segonzac (2018: 89, figs 9AH; 10A-E; 11A-E) and remarks on K. kulolasi n. gen., n. sp. In Kallograea jolliveti n. comb., the pigmented spot near the base of the fixed finger and more or less in continuity with the dark colour of the fixed finger, and present on both chelae in both sexes ( Figs 8C; 9C, D), recalls the distinctly coloured, more or less purplish, oval spot of Bythograea microps Saint Laurent, 1984 , located practically in the same place and also present in both sexes ( Saint Laurent 1984: pl. 1F; Guinot & Segonzac 2006b: fig. 5). In addition to the similarly coloured spot on the cheliped palm, these two species are both relatively small; but, whereas B. microps shows only a drastic reduction of the eyestalks ( Saint Laurent 1984: 386; 1988; Guinot & Segonzac 2006b: fig. 2), K. jolliveti n. comb. is entirely blind: the eyestalks are absent, the podophthalmite is fused to the floor of the orbital region, and the cornea is absent, without any visible pigment ( Fig. 8B).

DISTRIBUTION

Kallograea jolliveti n. comb. has a wide distribution in the western Pacific: initially, North Fiji and Lau Basins, now Kulo Lasi Volcano and Manus Basin.

COMPARISON BETWEEN KALLOGRAEA KULOLASI N. GEN., N. SP. ( Figs 4-7) AND K. JOLLIVETI N. COMB. ( Figs 8, 9) Kallograea kulolasi n. gen., n. sp. can easily be distinguished from K. jolliveti n. comb. by the suborbital region being glabrous or almost so ( Figs 4E; 5A; 6E) (vs densely setose in K. jolliveti n. comb.; Fig. 8B); median lobe of the posterior epistomial margin being obtusely triangular, with the lateral margins concave ( Figs 4E; 5C; 6E) (vs median lobe more acutely triangular with lateral margins gently sinuous to almost straight in K. jolliveti n. comb.; Fig. 8B); the mxp3 completely closes the buccal cavity across the anterior part, with the distal and external margins of the merus almost touching the pterygostomial lobe ( Figs 4E; 5C; 6E) (vs distinct gap between the distal and external margins of the merus and the pterygostomial lobe in K. jolliveti n. comb.; Fig. 8B); the P2-P5, in particular the meri, are distinctly longer and more slender ( Figs 4 A-C; 6A, B) (vs shorter and stouter in K. jolliveti n. comb.; Figs 8A; 9A); the ventral margins of P2–P4 have only scattered setae (vs with dense tomentum in K. jolliveti n. comb.); in both sexes, the dorsal margin of palm as well as the upper third or half of the outer surface (including the superior margin) and the upper third of the inner surface of adult male palm are densely setose but the rest of the inner surface is glabrous ( Figs 4 A-C; 5C-F; 6A-D) (vs dorsal and outer surfaces glabrous although the inner surface is densely setose in K. jolliveti n. comb.; Figs 8A, C-F; 9A, C-E); there is no spot at the base of the male pollex ( Figs 5C, E; 6C) (vs with a visible pale-coloured spot in K. jolliveti n. comb.; Figs 8C, D; 9, D); the fingers of the male chela are relatively shorter than the palm, with the pigmentation extending along the distal third or quarter ( Figs 5 C-F; 6C, D) (vs the fingers of the male chela are as long as the palm, with the pigmentation extending along the distal half in K. jolliveti n. comb.; Figs 8A, C-F; 9A, C-E); the male thoracic sternum is proportionately wider, in relation with the short body of the species ( Fig. 4B, D, F) (vs thoracic sternum less wide in K. jolliveti n. comb.; Figs 8G; 9G); the longitudinal median line on sternite 8 is relatively deeper ( Figs 4F; 6F) (vs median line less deep in K. jolliveti n. comb.; Figs 8H; 9G); the male pleon is distinctly wider, with the telson semicircular in form ( Fig. 4B, D) (vs pleon less wide with the telson more triangular in K. jolliveti n. comb.; Fig. 8G); the G1 is more strongly curved outwards ( Figs 4G; 7A, B) (vs distinctly straighter in K. jolliveti n. comb.; Fig. 8I, J); the G2 is proportionately much longer in K. kulolasi n. gen., n. sp., with the flagellum slightly longer than basal part ( Figs 4H; 7E) (vs G2 relatively shorter, with a small flagellum in K. jolliveti ; Fig. 8K); and the medially positioned subhemispherical vulva occupying slightly more than half the space of sternite 6 ( Fig. 6F) (vs relatively larger, ovate and occupying most of the space of sternite 6, with the anterior edge touching sternal suture 5/ 6 in K. jolliveti n. comb.; Fig. 11G).

The differences in the structure of the posterior epistomial margin (i.e., whether the mxp3 completely closes the anterior part of the buccal cavity), shape of the male telson, the very different proportions of the flagellum and basal part of the G2, and the structures of the vulvae, however, are significant, and may suggest K. jolliveti n. comb. is not a member of Kallograea n. gen. That being said, the flat carapace, wide male anterior thoracic sternum, wide male pleon, and elongate male chelipeds with the rounded finger tips are important shared characters with K. kulolasi n. gen., n. sp., and indicate that placing Austinograea jolliveti in Kallograea n. gen. is the best decision for the time being.

It is interesting to find two distinct species in a narrow perimeter on the periphery of the circular caldera of the Kulo Lasi Vulcano, an area with a diameter of only 5 km. The biota in this area, however, is known to be very dense and varied. Kallograea kulolasi n. gen., n. sp. seems confined to the Kulo Lasi Volcano, whereas the geographic range of K. jolliveti now extends from west to east, up to the Manus Basin ( Figs 1-3).

COMPARISON BETWEEN KALLOGRAEA N. GEN. ( Figs 4-9) AND AUSTINOGRAEA HESSLER & MARTIN, 1989 ( Figs 10; 11)

The genus Austinograea is known from four species from the western Pacific: the type species A. williamsi Hessler & Martin, 1989 , A. alayseae Guinot, 1990 (note that genetic differences have been found between individuals of A. alayseae from the Tofua Arc and the Manus Basin, see Kim et al. 2014), A. hourdezi Guinot & Segonzac, 2018 , and A. chubacarc Guinot, 2025 . A fifth species, A. rodriguezensis Tsuchida & Hashimoto, 2002 , occurs in the western Indian Ocean.

Austinograea williamsi (see Hessler & Martin 1989: figs 1, 2, 4, 5a, 6a, 7a, 8b, 9-11, 13a, 14a-d; Tsuchida & Fujikura 2000: figs 3, 5, 6, 8; Segonzac 2006: figs 1-4; see also Desbruyères et al. 2006; Kojima & Watanabe 2015: figs 25.1, 25.2), found in abundance in beds of the snail Alviniconcha hessleri Okutani & Ohta, 1988 that is common at the vent openings, is endemic to the Mariana Trough in the north-western Pacific, in the Mariana Back-Arc Basin, just west of the Mariana Island Arc. It should be noted that the ocular region of adult A. alayseae is not significantly different from that of adult A. williamsi ( Hessler & Martin 1989: fig. 4): the orbital region is only more recessed in A. williamsi , but, likewise, the eye is vestigial, fused to the orbital floor, and replaced by a small oval region in the posterior orbital wall lateral to the antenna, and with a trace of cornea that is more or less discernible and virtually unpigmented (sometimes a small spot) (cf. Hessler & Martin 1989: figs 4, 5a for A. williamsi ; Guinot 1990: fig. 1A, B for A. alysaeae ). A key to the species of Austinograea was provided by Guinot & Segonzac (2018: 96). One species described from the western Pacific, Austinograea yunohana Takeda, Hashimoto & Ohta, 2000 , was subsequently transferred by McLay (2007) to his new genus Gandalfus (see below).

Kallograea n. gen. is markedly different from Austinograea in that the dorsal surface of the carapace is almost flat ( Figs 4A, C, E; 5A; 6A, E) (vs surface gently but distinctly convex in frontal view in Austinograea ; Figs 10A, C; 11A); the posterior margin of the epistome is relatively wider ( Figs 4E; 6E) (vs transversely narrower in Austinograea ; Fig. 10C); the ischium of the mxp3 is distinctly elongate ( Fig. 5B) (vs shorter in Austinograea , except in A. williamsi ; Fig. 10H); the merus of the mxp3 is subtriangular in shape, with the anterior part much produced ( Figs 4E; 5B; 6E) (vs subquadrate in Austinograea , except in A. williamsi ; Fig. 10H); the male anterior thoracic sternum is short and very wide ( Fig. 4B, D, F) (vs transversely narrower in Austinograea ; Fig. 10B, H, I); the adult male chelipeds are distinctly more elongate and slender, especially the merus that is longer, distinctly extending well beyond the carapace margin, and slender, narrow on its whole length, and regularly toothed on the dorsal margin ( Figs 4 A-C; 5C, D) (vs distinctly shorter and stouter, of moderate length and width in Austinograea [the chelipeds are relatively longer in A. willliamsi but still distinctly shorter than in Kallograea n. gen.]; Fig. 10A, B); the adult male ambulatory legs are proportionately more slender and elongate, especially the merus and propodus ( Fig. 4 A-C) (vs relatively shorter and stouter in Austinograea ; Fig. 10A, B); the male sternopleonal cavity is gently concave, relatively wide distally and without a concavity for the G1 tip ( Fig. 4F) (vs cavity relatively deeper, relatively narrowing distally Fig. 10I, sometimes with a distinct depression for the G1 tips, in Austinograea ); and the almost straight G1 is positioned more or less longitudinally with the distal parts of each not overlapping ( Figs 4F, G; 7 A-D) (vs distinctly sinuous or straight with the distal parts of each overlapping to some degree in Austinograea ( Fig. 10I) [condition not clear for A. rodriguezensis , cf. Tsuchida & Fujikura 2000: fig. 8].

The form of the median lobe on the posterior epistomial margin of K. kulolasi n. gen., n. sp., being obtusely triangular ( Figs 4E; 6E), is different from that of Austinograea species (acutely triangular in form; Fig. 10C); and is more similar in condition to that in Gandalfus ( Figs 12 B-D; 14B, C; 15B; 16B), although the overall margin of K. kulolasi n. gen., n. sp. is distinctly wider. On the other hand, the median lobe of the margin in K. jolliveti n. comb., being acutely triangular ( Figs 8B; 9B), is more similar in form to that of Austinograea species, although the overall margin is still wider in K. jolliveti n. comb.

In Austinograea alayseae Guinot, 1990 , the extremities of the G1 join at the tips at the end of the sternopleonal cavity in situ and are positioned in a small deep depression (cf. Guinot 1990: 884, 891, fig. 2C; Guinot & Segonzac 2006a: fig. 5). In A. hourdezi Guinot & Segonzac, 2018 ( Guinot 1990: figs 4C, 6C) and A. williamsi ( Fig. 10I), the G1 tips also cross distally and are positioned in a narrow channel at the anterior part of the sternopleonal cavity. In contrast, in Kallograea n. gen., the obliquely directed G1 have the tips well separated and the anterior part of the sternopleonal cavity is proportionally wider, flatter and without a special distal depression to receive the G1 tips ( Figs 4F; 8H).

Another significant distinction between Austinograea and Kallograea kulolasi n. gen., n. sp. is observed in the length of the flagellum of G2. It is much shorter than the basal article in Austinograea species ( Fig. 10I) and is as long as the basis in Kallograea kulolasi n. gen., n. sp. ( Figs 4H; 7E). In K. jolliveti n. comb., the G2 is proportionately shorter and the flagellum much shorter than that in K. kulolasi n. gen., n. sp. ( Fig. 8K); Guinot & Segonzac 2018: figs 9D, 11C-E).

No other Austinograea species, except A. williamsi , in which the male crusher has rounded finger tips ( Fig. 10B, D, G), has finger tips as blunt as those on the crusher of Kallograea n. gen. Their overall cheliped structures, however, differ significantly, with that of Kallograea n. gen. being elongate and slender ( Figs 4 A-C; 5C-F; 8A, C-F) and that of Austinograea , short and stout ( Fig. 8A, B, D, G).

The above-discussed differences justify the transfer of Austinograea jolliveti into Kallograea n. gen., albeit with some reservations (see previously: Comparison between Kallograea kulolasi n. gen., n. sp. and K. jolliveti n. comb.).

COMPARISON BETWEEN KALLOGRAEA N. GEN. ( Figs 4-9) AND GANDALFUS MCLAY, 2007 ( Figs 12-16)

The type species, Gandalfus puia , has been collected from hydrothermal sites of the Kermadec Arc in the south-west Pacific Ocean, the longest underwater volcanic ridge on the planet, particularly in three active volcanoes between 30°12’S- 35°44’S and 181°33’E- 178°29’E (at 270- 239 m, at 1604-1647 m, and at 337 m). The ridge, which forms the base of the Kermadec Islands, is linear for about 1000 km and is a prolongation of the Tonga ridge. The Tonga-Kermadec Ridge is underlying the Tonga-Kermadec island arc and, on its western side, it is flanked by the back-arc-basin, the Lau Basin, which is at the boundary of the Australian and Pacific Plates ( De Ronde et al. 2001; Wright 2001; Wright et al. 2002; Hauff et al. 2021).

The carapace of adult Gandalfus species is distinctly higher, with the dorsal surface more convex ( Figs 12A, C, D; 13A, D; 14A, B; 15A; 16A) compared to those of Kallograea spp. which are lower and flatter ( Figs 4A, C, E; 5A; 6A, E; 8A, B; 9A). The chelipeds of G. puia and G. yunohana are relatively short, have a short merus that is irregularly serrated and triangular in cross section, and a granulous and glabrous palm ending in relatively acute fingers that are armed with several proximal teeth of variable size, including one larger tooth at midlength of fixed finger ( Figs 12A, F, G; 13A; 14A, E-G; 15E-H; 16A, D, E) (vs adult male chelipeds distinctly more elongate, with the merus distinctly longer, slender along its entire length, with the dorsal margin dentate, and extending well beyond carapace margin; the stout palm possessing setal patches and ending in thick and blunt fingers, and on the major chela, there is only a molariform tooth on the fixed finger in Kallograea n. gen.; Figs 4 A-C; 5C-F; 8A, C-F). While adult Gandalfus spp. are generally larger (carapace width: 36.7 mm in G. puia ; 42.2 mm in G. yunohana ), we have subadult specimens of G. puia (e.g., female 10.4 × 14.3 mm, ZRC 2024.0726, ex MNHN-IU-2024-6553) which are comparable in size to the two Kallograea species, but these differences remain valid.

McLay (2007: fig. 2D-F, table 2) recognised a new genus for his new species, Gandalfus puia , arguing that its G2 was quite different from those of Austinograea s. str. In G. puia , the G2 is approximately as long as the G1, with the flagellum as long as or longer than the basal article. Because of this character, McLay (2007) transferred Austinograea yunohana Takeda, Hashimoto & Ohta, 2000 to Gandalfus (see Takeda et al. 2000: 164, 168, figs 4I, 6c, e) and, in doing so, he restricted Austinograea for species in which the G2 is clearly shorter than the G1, and has a shorter flagellum as well. The G2 is distinctly less than half the length of the G 1 in A. williamsi ( Fig. 10I; Hessler & Martin 1989: fig. 14a; Tsuchida & Fujikura 2000: fig. 6; Guinot & Segonzac 2006c: fig. 4) and A. rodriguezensis (cf. Tsuchida & Hashimoto 2002: fig. 8; Tsuchida 2006: fig. 3); about half the length of the G 1 in A. hourdezi Guinot & Segonzac, 2018 (cf. Guinot & Segonzac 2018: fig. 6D, E); and more than half the length of the G1 (which is curved and armed with spiniform setae along its whole length) in A. alayseae Guinot, 1990 (cf. Guinot 1990: fig. 3A-C; Guinot & Segonzac 2006a: fig. 6).

The discovery of the relative lengths of G2/G 1 in Kallograea kulolasi n. gen., n. sp. and K. jolliveti n. comb. reinforces the value of this character as a key taxonomic index. In both species of Kallograea n. gen., the G2 is curved, and is as long as or shorter than the G1 ( Figs 4H; 7E; 8K); with the flagellum slightly longer than the basal part. This is also one of the main characters that distinguishes Gandalfus from Austinograea .

Another distinctive character of Gandalfus documented by McLay (2007), the slightly sinuous posterior epistomial margin (vs the strongly sinuous margin in Austinograea ; see Tsuchida & Hashimoto 2002: fig. 3), was difficult to appreciate because, unfortunately, the shape of the epistome of G. puia was not clearly illustrated in McLay’s paper. Our examination of the two genera shows that the median lobe of the margin is obtusely triangular in Gandalfus ( Figs 12 B-D; 14B, D; 15B; 16B, C) but more distinctly acutely triangular in Austinograea ( Fig. 8C; Tsuchida & Hashimoto 2002: fig. 3). The posterior epistomial margin in both Kallograea species is distinctly wider than those of Gandalfus or Austinograea . As discussed earlier under Austinograea , the median lobe of this margin is obtusely triangular in K. kulolasi n. gen., n. sp. ( Figs 4E; 5C; 6E).

McLay (2007: 7) described the vulva in a female of Gandalfus puia (carapace width 36.5 mm) as “slit-like”, oriented along anterior posterior body axis, not operculate, but he did not give an illustration. Gandalfus puia has a rounded vulva, with a distinct pointed tubercle at the anterior edge, which may be interpreted as a narrow sternal cover ( Fig. 13F), as that of G. yunohana illustrated by Takeda et al. (2000: 166, fig. 4 E, as Austinograea yunohana ; Fig. 16G). The vulva of K. kulolasi n. gen., n. sp. ( Fig. 6F) and K. jolliveti n. comb. ( Fig. 9G; Guinot & Segonzac 2018: fig. 10E, as Austinograea jolliveti ) is large, occupying most of the surface of sternite 6, and rounded, without any trace of an anterior tubercle. The vulva of Austinograea species is rounded, closed by soft membrane: in A. williamsi ( Fig. 9B) and A. hourdezi ( Guinot & Segonzac 2018: fig. 10E), without any trace of an anterior tubercle.

The larvae of Gandalfus yunohana were reported on by Nakajima et al. (2010) and Hamasaki et al. (2010). The complete mitogenome of G. yunohana , from the Nikko Seamount on the Izu-Ogasawara Ridge, was reported by Yang et al. (2010: fig. 3) who showed that it had highly conserved characteristics and appeared to be related to brachyurans such as Pseudocarcinus gigas (Lamarck, 1818) . Pseudocarcinus gigas is at present in its own family (see Ng & Davie 2020), and this supposed relationship needs to be revisited. The complete mitochondrial genome of G. puia , from the Tonga Arc, was obtained by Kim et al. (2015: fig. 1), showing that the genetic data of this taxon is distinct from that of Austinograea s. str. The phylogenetic tree of Wang et al. (2019: fig. 1) includes Gandalfus puia , G. yunohana , Austinograea alayseae , A. rodriguezensis and Segonzacia mesatlantica (Williams, 1988) , and they show the same separation, indicating Gandalfus and Austinograea are separate genera (see also the Bayesian inference tree in Ma et al. 2024). Barcoding sequences of the mitochondrial COI gene of G. yunohana , from four vent fields (including two on the Izu Arc, one on the northern Mariana Arc and one in the Okinawa Trough), have shown a similar genetic diversity of populations on the Izu and northern Mariana Arcs and a sharing of the dominant haplotypes, without genetic subdivision regardless of the habitat depth, the whole suggesting a high dispersal capability for G. yunohana (cf. Watanabe et al. 2020).