Parashiela soniae, Amati & Giulio & Oliverio, 2023

Amati, Bruno, Giulio, Andrea Di & Oliverio, Marco, 2023, Shallow-water Rissoidae of the genera Alvania Risso 1826 Haurakia Iredale 1915 Parashiela Laseron 1956 Simulamerelina Ponder 1985 and Subestea Cotton 1944 Gastropoda Caenogastropoda Rissooidea from French Polynesia with the description of a new deep-water genus, Zoosystema 45 (25), pp. 803-892 : 850-853

Parashiela soniae n. sp.

( Figs 32 ; 33 ; 51C ; 53N ; Tables 4 ; 5; 6)

urn:lsid:zoobank.org:act:A878ED1E-73A7-4421-A6B5-A47F77EA564F

TYPE MATERIAL. — Holotype. Marquesas • dd (height 1.17 mm, width 0.73 mm, Figs 32 A-C; 33; 53N); Nuku Hiva , Les 4 grottes, PAKAIHI I TE MOANA Stn MQ2-GR; 8°56’13”S, 140°7’15”W; 20-23 m; 07, 11-13, 29.I.2012; MNHN-IM-2000-38720 .

Paratypes. Marquesas • 8 dd, 7 lv ( Fig. 32 D-H); same locality data as holotype; MNHN-IM-2000-38721 .

TYPE LOCALITY. — Marquesas: Nuku Hiva, Les 4 grottes, PAKAIHI I TE MOANA Stn MQ2-GR; 8°56’13”S, 140°7’15”W; 20- 23 m.

OTHER MATERIAL EXAMINED. — Marquesas • 3 dd, 4 lv; Tahuata PAKAIHI I TE MOANA Stn MQ12-M; 9°58’12”S, 139°7’33”W; 0-1 m; 15.I.2012; MNHN • 4 dd, 6 lv; Ua Pou, Hatu Iti cave , PAKAIHI I TE MOANA Stn MQ 27-GR; 9°23’41”S, 140°7’44”W; 5-22 m; 25.I.2012; MNHN • 1 dd; Nuku Hiva , Anao Bay; 8°49’40”S, 140°3’32”W; beached; coll. MB • 5 dd, 10 lv; Nuku Hiva , Matateteiko, PAKAIHI I TE MOANA Stn MQ 3-GR; 8°55’58”S, 140°13’33”W; 20-25 m; 8.I.2012; MNHN • 1 lv; Hatutu, Hatutaa Cave , PAKAIHI I TE MOANA Stn MQ 32-GR; 7°54’25”S, 140°33’57”W; 17-22 m; 27.I.2012; MNHN • 1 dd; Banc Hinakura , PAKAIHI I TE MOANA Stn MQ 31-ACH1 2; 7°55’58”S, 140°58’58”W; 120-300 m; 7.I.2012; MNHN .

DISTRIBUTION AND SYMPATRY. — Parashiela soniae n. sp. is at present known in the South Pacific Ocean from the Marquesas, with 28 live specimens collected (along with 23 empty shells) in 0-25 m, and an empty shell from Banc Hinakura in 120-300 m ( Fig. 51C ). No congener collected sympatrically.

ETYMOLOGY. — Named after Sonia Turchi, wife of one of the authors (ADG).

DIAGNOSIS. — Parashiela of small size for the genus (height c. 1 mm). Protoconch paucispiral with strong spiral cordlets. Protoconch-teleoconch boundary very marked and sinuous, with slight adapical detachment. Umbilical fissure evident. Teleoconch microsculpture of sparse dense microgranules.

DESCRIPTION OF HOLOTYPE

Shell ( Figs 32 A-C; 33A; 53N)

Small for the genus, height 1.17 mm, width 0.73 mm, height/ width ratio 1.60, ovate-conical, rather robust, thick.

Protoconch ( Fig. 33D, E )

Paucispiral, with nucleus moderately intorted, of 1.1 convex whorls, height 0.225 mm, nucleus diameter 0.075 mm, first half whorl diameter 0.175 mm, maximum diameter 0.250 mm. Six equidistant strong spiral cordlets made of tightly fused granules (less tightly on nucleus and near the protoconch-teleoconch boundary), the last abapical partially covered by the first teleoconch whorl; an additional adapical thinner cordlet of smaller and less tightly fused granules ( Fig. 33D, E ). Protoconch-teleoconch boundary very marked, sinuous, with slight adapical detachment ( Fig. 33D, E ).

Teleoconch

Of 2.75 convex whorls with weak double anglulation on the whorls. Axial sculpture on the last whorl of 14 orthocline and thin ribs, reaching the base and entering the umbilical fissure. Interspaces twice as wide as the axial ribs. Absence of macro spiral sculpture. Microsculpture of dense microgranules vaguely arranged in spiral series ( Fig. 33B, C ). Umbilical fissure evident. Aperture round-ovate, height 0.50 mm, height/ aperture height ratio 2.34; peristome duplicated; outer lip slightly prosocline, internally smooth, externally very thickened and with numerous growth striae; columellar lip slightly angled in the middle.

Colour

Colouration white-yellowish.

Operculum and soft parts

Operculum typical for the genus. Soft parts not examined.

VARIABILITY

Based on the examined material, the variability is low (see Table 5 and Appendix 14).

REMARKS

Parashiela soniae n. sp. is the first species of the genus formally described, with paucispiral protoconch, indicating non-planktotrophic larval development. However, an undescribed Parashiela with a protoconch paucispiral and spirally sculptured, from Madagascar (Indian Ocean, MNHN) was reported by Ponder (1985: 51); another species from Papua New Guinea, https://ingokurtz.jimdofree.com/mollusca-weichtiere/rissoidae/ also has a paucispiral protoconch; it differs from P. soniae n. sp. in the presence of an evident subsutural shoulder, absent or very narrow in P. soniae n. sp.; the prosocline axial ribs, orthocline or slightly prosocline in P. soniae n. sp.; the umbilical fissure very narrow or closed, clearly evident in P. soniae n. sp.

Parashiela expansilabrum n. sp. differs from P.soniae n. sp. in the multispiral protoconch (vs paucispiral in P. soniae n. sp.); the larger size (height 1.12-1.55 mm, mean 1.35 vs height 0.93-1.17 mm, mean 1.06 in P. soniae n. sp.); the more numerous axial ribs (18 vs 14 in P. soniae n. sp.); the broader base; the presence of a subsutural cord on the first whorls of teleoconch, absent in P. soniae n. sp.

Parashiela liddelliana ( Hedley, 1907) differs from Parashiela soniae n. sp. in the multispiral protoconch (vs paucispiral in P. soniae n. sp.); the more numerous axial ribs (20 vs 14 in P. soniae n. sp.).

Parashiela rimatara n. sp. differs from P. soniae n. sp. in the multispiral protoconch (vs paucispiral in P. soniae n. sp.); the larger size (height 1.38-1.53 mm vs height 0.93-1.17 mm in P. soniae n. sp.); the thinner and more numerous axial ribs (26 vs 14 in P. soniae n. sp.); the subsutural cord on the first teleoconch whorls, absent in P. soniae n. sp.; the slightly wider umbilical fissure; the different teleoconch microsculpture, formed by threads arranged in dense spiral rows vs dense microgranules vaguely arranged in spiral series in P. soniae n. sp.

Parashiela rotundata n. sp. differs from P. soniae n. sp. in the multispiral protoconch (vs paucispiral in P. soniae n. sp.); the wider umbilical fissure; the microsculpture of teleoconch formed by groups of 3-4 thin threads separated by micro furrows vs dense microgranules vaguely arranged in spiral series in P. soniae n. sp.

Figures

FIG. 32. — Parashiela soniae n. sp.: A-C, holotype, Marquesas, Nuku Hiva, 20-23 m, height 1.17 mm, width 0.73 mm, MNHN-IM-2000-38720; D-F, paratype, Marquesas, Nuku Hiva, same station as holotype, height 1.15 mm, MNHN-IM-2000-38721; E, F, details of the first whorls; G, paratype, Marquesas, Nuku Hiva, same station as holotype, 20-23 m, height 1.09 mm, MNHN-IM-2000-38721; H, paratype, Marquesas, Nuku Hiva, same station as holotype, height 0.95 mm, MNHN-IM-2000-38721. Scale bars: E, F, 20 μm.

FIG. 33. — Parashiela soniae n. sp.: A-E, holotype, Marquesas, Nuku Hiva, 20-23 m depth, height 1.17 mm, width 0.73 mm, MNHN-IM-2000-38720: shell (A); detail of the last whorl microsculpture, subsutural-median portion (B, C), details of the first whorls (D, E). Scale bars: B, 10 μm; C, 2 μm; D, E, 40 μm.

FIG. 51. — Distribution maps of the Polynesian species of Haurakia Iredale,1915, and Parashiela Laseron, 1956: A, Haurakia marmorata (Hedley,1907); B, Parashiela ambulata Laseron, 1956; C, Parashiela expansilabrum n. sp.; D, Parashiela obesula n. sp. (*), Parashiela rimatara n. sp. (○), Parashiela rotundata n. sp. (●), Parashiela soniae n. sp. (●).

FIG. 53. — Alvania Risso,1826,Ellenstrongia n. gen., Haurakia Iredale,1915,Parashiela Laseron,1956,Simulamerelina Ponder,1985 and Substea Cotton,1944:A, Alvania letouneuxi n.sp., holotype,MNHN-IM-2000 38703, height 1.60 mm; B, Alvania herosae n. sp., holotype,MNHN-IM-2000-38704, height 2.02 mm;C, Alvania herosae n.sp.(morph B),MNHN,height 2.16 mm;D, Alvania parvimaculata n. sp.,holotype,MNHN-IM-2000-38706, height 1.65 mm;E, Alvania prosocostata n.sp., holotype, MNHN-IM-2000-38708 height 2.05 mm; F, Alvania uapou n. sp., holotype, MNHN-IM-2000-38710, height 1.70 mm; G, Ellenstrongia tarasoc n. gen., n. sp., holotype,MNHN-IM-2000-39448, height 4.50 mm; H, Haurakia marmorata (Hedley, 1907), Society Islands,height 1.95 mm, coll. JL; I, Parashiela ambulata Laseron, 1956, Australes: Rapa Pointe Kauira, height 1.60 mm, MNHN; J, Parashiela expansilabrum n. sp. holotype, MNHN-IM-2000-38712 height 1.47 mm; K, Parashiela obesula n. sp. holotype, MNHN-IM-2000-38714, height 1.32 mm; L, Parashiela rimatara n. sp. holotype, MNHN-IM-2000-38716, height 1.47 mm; M, Parashiela rotundata n. sp. holotype, MNHN-IM-200038718-, height 1.10 mm; N, Parashiela soniae n. sp., holotype, MNHN-IM-2000-38720, height 1.17 mm; O, Simulamerelina australes n. sp. holotype, MNHN-IM-2000-38722, height 2.47 mm; P, Simulamerelina densestriata n. sp., holotype, MNHN-IM-2000-38724, height 2.45 mm; Q, Simulamerelina gracilis n. sp., holotype, MNHN-IM-2000-38726, height 2.45 mm; R, Simulamerelina lepteseiras n. sp., holotype, MNHN- IM-2000-38727, height 1.47 mm; S, Simulamerelina micrometrica n. sp., holotype, MNHN-IM-2000-38728, height 1.33 mm; T, Simulamerelina tuamotu n. sp. holotype, MNHN-IM-2000-38730, height 1.57 mm; U, Subestea moruroa n. sp., holotype, MNHN-IM-2000-38732, height 1.96 mm.