Benthonella boucheti, Amati & Giulio & Oliverio, 2022

Amati, Bruno, Giulio, Andrea Di & Oliverio, Marco, 2022, Deep-water Rissoidae of the genera Benthonella Dall, 1889 and Benthonellania Lozouet, 1990 (Gastropoda, Caenogastropoda, Rissooidea) from French Polynesia, Zoosystema 44 (12), pp. 335-389 : 338-343

Benthonella boucheti n. sp.

( Figs 2 A-G; 5A-E; 25A; 26A; Tables 1 ; 2)

urn:lsid:zoobank.org:act:20D288CF-46E8-4160-B602-22886ADDFE4C

TYPE MATERIAL. — Holotype. Tarava Seamounts • dd (height 4.32 mm, width 2.75 mm, Figs 6A ; 7 A-C); Mont Honu , TARASOC Stn DW3340 ; 18°24’S, 154°09’W; 787-798 m; MNHN- IM-2000-37666 .

Paratypes • 22 dd; same locality data as holotype; MNHN- IM-2000-37667 .

TYPE LOCALITY. — Tarava Seamounts, Mont Honu, TARASOC Stn DW3340, 18°24’S, 154°09’W, 787- 798 m.

OTHER MATERIAL EXAMINED. — Tarava Seamounts • 2 dd; Mont ‘ Otaha, TARASOC Stn DW 3333; 18°45’S, 152°18’W; 795-975 m; 26.IX.2009; MNHN • 3 dd; Mont ‘ Otaha,TARASOC Stn DW 3328; 18°46’S, 152°15’W; 788-836 m; 26.IX.2009; MNHN • 1 dd; Mont ‘ Otaha, TARASOC Stn DW 3331; 18°45’S, 152°17’W; 766 m; 26.IX.2009; MNHN.

Marquesas • 2 dd; Fatu Hiva, MUSORSTOM 9 Stn DR 1247; 10°34’S, 138°42’W; 1150-1250 m; 1.IX.1997; MNHN .

Australes • 9 dd; Banc Président Thiers , BENTHAUS Stn DW 1933; 24°41’S, 146°01’W; 500-850 m; 14.XI.2002; MNHN • 2 dd; Récif Neilson , BENTHAUS Stn DW 1925; 27°00’S, 146°05’W; 560- 790 m; 12.XI.2002; MNHN • 15 dd; Récif Neilson , BENTHAUS Stn DW 1925; 27°00’S, 146°05’W; 560-790 m; 12.XI.2002; MNHN • 21 dd; South coast of Rurutu , BENTHAUS Stn DW2010 ; 22°32’S, 151°21’; 520-950 m; 24.XI.2002; MNHN • 1 dd; Tubuai , BENTHAUS Stn DW 1961; 23°21’S, 149°34’; 470-800 m; 19.XI.2002; MNHN • 4 dd; Tubuai , BENTHAUS Stn DW 1955; 23°19’S, 149°26’W; 750-850 m; 18.XI.2002; MNHN • 6 dd; Tubuai , BENTHAUS Stn DW 1956; 23°18’S, 149°27’W; 600-990 m; 18.XI.2002; MNHN • 1 dd; Tubuai , BENTHAUS Stn DW 1962; 23°21’S, 149°33’W; 470-800 m; 19.XI.2002; MNHN • 3 dd; North of Raivavae , BENTHAUS Stn DW 1943; 23°49’S, 147°39’W; 950 m; 15.XI.2002; MNHN • 3 dd; Marotiri , BENTHAUS Stn DW 1886; 27°51’S, 143°32’W; 620-1000 m; 6.XI.2002; MNHN • 2 dd; Marotiri , BENTHAUS Stn DW 1887; 27°52’S, 143°33’W; 750-1000 m; 6.XI.2002; MNHN • 9 dd; Banc Arago, BENTHAUS Stn DW 1981; 23°21’S, 150°43’W; 650-1150 m; 21.XI.2002; MNHN • 15 dd; Rimatara , BENTHAUS Stn DW 2021; 22°37’S, 152°49’W; 1200-1226 m; 25.XI.2002; MNHN • 9 dd; Rimatara , BENTHAUS Stn DW 2020; 22°37’S, 152°49’W; 920-930 m; 25.XI.2002; MNHN • 9 dd; East coast of Rurutu, BENTHAUS Stn DW 2004; 22°28’S, 151°19’W; 430-850 m; 24.XI.2002.

Tuamotu • 1 dd; between Tikehau and Rangiroa, TARASOC Stn DW 3349; 15°05’S, 148°03’W; 976-997 m; 30.IX.2009; MNHN .

DISTRIBUTION AND SYMPATRY. — Benthonella boucheti n. sp. is known from the South Pacific Ocean, in the Tarava Seamounts (Mont Honu, Mont ‘Otaha), Australes (Banc Président Thiers, Récif Neilson, South Coasts of Rurutu, East coasts of Rurutu, Tubuai, North of Raivavae, Marotiri, Banc Arago, Rimatara), Marquesas (Ile Fatu Hiva), Tuamotu (between Tikehau and Rangiroa), with empty shells collected in 430-1250 m depth ( Fig. 25A ).

Benthonella boucheti n. sp. is sympatric with Benthonellania maestratii n. sp. at the Australes (Récif Neilson, South coast of Rurutu); with Benthonella communis n. sp. at the Australes (Banc Président Thiers, Récif Neilson, South Coasts of Rurutu, East coasts of Rurutu, Tubuai, North of Raivavae, Marotiri, Banc Arago, Rimatara), Tuamotu (between Tikehau and Rangiroa); with Benthonellania bouteti n. sp. at the Tarava Seamounts (Mont Honu and Mont ‘Otaha), Australes (Banc Président Thiers, Récif Neilson, South Coasts of Rurutu, East coasts of Rurutu, Banc Arago, Rimatara. Tubuai), Tuamotu (between Tikehau and Rangiroa); with Benthonellania tarava n. sp. at the Tarava Seamounts (Mont Honu and Mont ‘Otaha), Australes (Rimatara, South coast of Rurutu, East coast of Rurutu), Tuamotu (between Tikehau and Rangiroa); with Benthonellania tuamotu n. sp. at the Tarava Seamounts (Mont ‘Otaha), Australes (Rimatara, South coast of Rurutu, Récif Neilson), Tuamotu (between Tikehau and Rangiroa); with Benthonellania lozoueti n. sp. at the Marquesas (Ile Fatu Hiva); with Benthonellania megan n. sp. at the Marquesas (Ile Fatu Hiva), Australes (Rimatara); with Benthonellania alis n. sp. at the Australes (East coast of Rurutu, South coast of Rurutu, Rimatara, Marotiri, Tubuai, Banc Président Thiers), Tarava Seamounts (Mont ‘Otaha, Mont Honu) ( Table 2).

ETYMOLOGY. — Named after Philippe Bouchet (MNHN), for his indefatigable work during decades, aimed at improving the knowledge of marine biodiversity.

DESCRIPTION OF HOLOTYPE.

Shell ( Figs 2 A-C; 5A-E)

Large for the genus, height 4.3 mm, width 2.7 mm, height/width ratio 1.57, ovate-conical, rather fragile, with broad last whorl.

Protoconch ( Figs 2G ; 5B, C, E )

Multispiral, dome-shaped, of 2.4 whorls, height 0.4125 mm, nucleus diameter 0.075 mm, first half whorl diameter 0.1375 mm, maximum diameter 0.60 mm; protoconch I with 4 threads, interspaces covered by microtubercles ( Fig.5C ); protoconch II with two pairs of spiral cordlets, and closely set axial micro-riblets in the interspace of the abapical pair ( Fig. 5B ). Protoconch-teleoconch, boundary indistinct, sinuous.

Teleoconch

Of 4.2 slightly convex whorls of slowly increasing height; suture incised, slightly canaliculate and wavy. Height last whorl 2.9 mm, height/height last whorl ratio 1.491. Axial sculpture of weak, flat, curved and prosocline ribs, half as broad as the interspaces, absent on the first half whorl, 20 on the last whorl, gradually vanishing at the base, prominent at suture, giving the whorls a coronated appearance ( Fig. 5E ). Spiral sculpture of 7 weak, narrow and very low, indistinct spiral cordlets, only on the base. Microsculpture of only growth striae ( Fig. 5D ). Umbilical chink present. Aperture pyriform, large, height 2.0 mm, height/height aperture ratio 2.162, peristome continuous, outer lip prosocline (broken), internally smooth. Columella arcuate, simple.

Colour

Coloration of teleoconch white, protoconch orange.

Operculum and soft parts

Unknown.

VARIABILITY

Only two full-grown intact specimens available; the variability seems low (see Table 1 and Appendix 1).

REMARKS

Benthonella boucheti n. sp. resembles the northeastern Atlantic and Mediterranean Benthonella tenella ( Jeffreys 1869: 204, pl. CI, fig. 7) for the conical outline with a broad last whorl, especially in the so-called ‘form fischeri Dall, 1889 ’ ( Ponder 1985: 63, figs 39A, B; Bouchet & Warén 1993: 699, figs 1643-1650; Lozouet 2014: 24, 31, figs 2R, S, and 7A-C), with its axial sculpture on the first teleoconch whorls (absent in the typical form). Benthonella boucheti n. sp. differs in its less rounded aperture, spiral sculpture on the base, and different apical sculpture: protoconch II with two pairs of spiral cordlets, in the interspaces of the abapical pair, confused and close axial micro riblets vs protoconch II with two thin spiral cordlets and a subsutural belt of microgranules in B. tenella .

Figures

FIG. 2. — Benthonella boucheti n.sp.:A-C, holotype,height 4.32 mm,width 2.75 mm,Tarava Seamounts:TARASOC Stn DW3340 787-798 m 18°24’S,154°09’W (MNHN- IM-2000-37666); D-G, specimen, height 3.75 mm, width 2.6 mm, Australes:BENTHAUS Stn DW1933 500-850 m 24°41’S, 146°01’W, MNHN. Scale bar: G, 0.50 mm.

FIG. 6. — Benthonellania precipitata (Dall, 1889) n. comb.: A-D, holotype (MCZ–7470), height 3.92 mm; D, detail of the first whorls; E, relevant page of the Catalogue of Mollusca in the Museum of Comparative Zoology (photo by Alana Rivera). Scale bar: D, 0.25 mm.

FIG. 7. — Benthonellania hertzogi (Thiele,1925),syntypes,Valdivia Stn 109 (ZMB–64981):A-C, syntype,height 2.85 mm (ZMB-64981);D-F, syntype,height 2.47 mm (ZMB-64981); G, original label; H, original drawings (Thiele 1925, 82, pl. 6, fig. 15, 16); I, J, syntype (A-C), detail of the first whorls. Scale bars: I, J: 0.25 mm.

FIG. 25. — Distribution maps of the Polynesian species of Benthonella Dall,1889 and Benthonellania Lozouet,1990: A, Benthonella boucheti n. sp.;B, Benthonella basistriata n. sp.; C, Benthonella communis n. sp.; D, Benthonellania bouteti n. sp.; E, Benthonellania alis n. sp.; F, Benthonellania tarava n. sp. (◯) and Benthonellania lozoueti n. sp. (); G, Benthonellania megan n. sp. (◯) and Benthonellania maestratii n. sp. (); H, Benthonellania tuamotu n. sp.

FIG. 5. — Benthonella spp. (SEM): A-E, Benthonella boucheti n. sp. holotype, MNHN-IM-2000-37666, Tarava Seamounts, height 4.32 mm: A, shell; B, C, detail of the protoconch microsculture; D, detail of the teleoconch sculpture spiral; E, detail of the first whorls; F, G, Benthonella basistriata n. sp. holotype, MNHN- IM-2000-37668, Tuamotu,height 2.0 mm:F, shell; G, detail of the protoconch microsculture;H-J, Benthonella communis n. sp., holotype,MNHN-IM-2000-37670, Tarava Seamounts: height 2.2 mm; H, shell; I, J, detail of the protoconch microsculture. Scale bars: B, 40 μm; C, J, 20 μm; D, E, I, 100 μm; G, 50 μm.