Alvania parvimaculata, 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 : 819-821

Alvania parvimaculata n. sp.

( Figs 14 ; 15 ; 49B ; 53D ; Tables 1 ; 2 )

urn:lsid:zoobank.org:act:6E5E2802-821A-46C4-8073-D298A8DC22FD

? Simulamerelina sp. 1 – Boutet et al. 2020: 240.

TYPE MATERIAL. — Holotype. Tuamotu • dd (height 1.65 mm, width 0.95 mm, Figs 14A, B ; 15 ; 53D ); Makemo , Passe Arikitamiro ; 16°37’15”S, 143°33’50”W; 1-20 m; Jean Letourneux leg.; MNHN-IM-2000-38706 .

Paratypes. Tuamotu • 5 dd. ( Fig. 14 C-F); same locality data as holotype; MNHN-IM-2000-38707 .

TYPE LOCALITY. — Tuamotu: Makemo, Passe Arikitamiro; 16°37’15”S, 143°33’50”W; 1- 20 m.

OTHER MATERIAL EXAMINED. — Tuamotu • 15 dd; Pinaki; 19°23’56”S, 138°40’1”W; 1 m; reef edge; coll. JL • 2 dd; Ana’a; 17°20’31”S, 145°30’32”W; coll. MB • 10 dd; Katiu; 16°21’43”S, 144°21’32”W; 1 m; reef edge; coll. JL • 25 dd; Makemo, Passe Arikitamiro, Nake; 16°37’1”S, 143°33’43”W; <1m; reef flat; coll. JL • 30 dd; Makemo; 16°34’26”S, 143°40’19”W; 1 m; reef edge after air-strip; coll. JL • 25 dd; Makemo; 16°36’21”S, 143°37’55”W; 1 m; reef edge between village and air-strip; coll. JL • 20 dd; Fangatao; 15°49’40”S, 140°54’10”W; 1 m; reef edge; coll. JL.

Society Islands • 1 dd; Tahiti, Arue; 17°31’15”S, 149°31’33”W; <1m; reef flat behind tomb of King Pomare V; coll. JL • 1 dd; Tahiti, E coast; 17°30’32”S, 149°25’58”W; 1 m; fringing reef flat of Papenoo ; coll. JL • 1 dd; Tetiaroa; 17°1’19”S, 149°36’3”W; 1 m; reef edge; coll. JL • 1 dd; Motu One; 15°48’21”S, 154°30’39”W; 1 m; reef edge; coll. JL.

DISTRIBUTION AND SYMPATRY. — The species is at present known in the South Pacific Ocean from the Tuamotu (Pinaki, Ana’a, Katiu, Makemo, Fangatao) and Society Islands (Tahiti, Tetiaroa, Motu One) ( Fig. 49B ).

Alvania parvimaculata n. sp. is sympatric with Alvania letourneuxi n. sp. at the Tuamotu (Makemo) ( Table 2 ).

ETYMOLOGY. — For the particular colouration with small spots, from the Latin parvus – small, maculatus – spotted.

DIAGNOSIS. — Alvania with small shell (<2 mm height); protoconch paucispiral; teleoconch spiral sculpture stronger than axial one; start of 2 spiral cordlets after protoconch-teleoconch boundary; colouration yellowish-white with small brown spots.

DESCRIPTION OF HOLOTYPE

Shell ( Figs 14A, B ; 15 ; 53D )

Small for the genus, height 1.65 mm, width 0.95 mm, height/ width ratio 1.74, robust, ovate-conical.

Protoconch ( Fig. 15B, C )

Paucispiral, of 1.20 convex whorls, height 0.250 mm, nucleus diameter 0.100 mm, first half whorl diameter 0.170 mm, maximum diameter 0.262 mm; devoid of sculpture. Protoconch-teleoconch boundary well marked.

Teleoconch

Of 3.10 convex whorls, suture impressed. Axial sculpture on last whorl of 16 slightly prosocline ribs, thinner than interspaces, gradually vanishing toward the base. Spiral sculpture of equidistant cordlets thinner than axials, 7 on the last whorl, 3 above the aperture, one on the suture line and 3 on the base. Cordlets II and III starting immediately after protoconch-teleoconch boundary, followed by subsutural cord I, thinner and less prominent. Medium sized rounded tubercles at the intersections; quadrangular interspaces. Microsculpture of weak spiral threads and growth lines ( Fig. 15B ). Umbilical fissure absent. Aperture piriform, height 0.70 mm, height/ aperture height ratio 2.36, peristome continuous and simple, outer varix moderately thickened; outer lip sharp, smooth internally, prosocline.

Colour

Colouration yellowish-white with sparse small brown spots on tubercles.

Operculum and soft parts

Unknown.

VARIABILITY

Maximum height 1.70 mm and minimum 1.25 mm. (See Table 1 and Appendix 4).

REMARKS

Alvania parvimaculata n. sp. is very similar to some species of the genus Simulamerelina Ponder, 1985 , like, e.g. Simulamerelina bermudensis ( Faber & Moolenbeek, 1987) , from which it differs mainly by the less slender outline, the simple and not duplicated peristome and the almost smooth protoconch, not sculptured by spiral keels.

Alvania hueti Bozzetti, 2017 , from Boucan-Canot, west coast of Réunion ( Bozzetti 2017: 6, 7, five unnumbered figures), is the most similar species. It differs from A. parvimaculata n. sp. in its more slender outline (holotype height/width ratio 1.86 vs 1.58-1.79 in A. parvimaculata n. sp.); in having three spiral cordlets on all whorls vs two cordlets on the first whorls and a smaller third one (subsutural) only on the last half of the last whorl; in the fewer axial ribs (12-13 vs 16-19 in A. parvimaculata n. sp.); in the protoconch sculptured with spirals vs smooth protoconch in A. parvimaculata n. sp.; in the dark subsutural spot on the last whorl before the aperture and the darker initial part of the protoconch (nucleus and part of the first whorl) vs absent spot and colourless apex in A. parvimaculata n. sp.

Alvania letourneuxi n. sp. has more axial ribs on the last whorl (21 vs 16-19 in A. parvimaculata n. sp.); more prominent rounded tubercles at the intersections; protoconch with fewer whorls (1 vs 1.15-1.20 in A. parvimaculata n. sp.), with smaller diameters (nucleus diameter 0.075 mm vs 0.100 - 0.125 mm; first half whorl diameter 0.150 mm vs 0.170 -0.212 mm; maximum diameter 0.200 mm vs 0.250 -0.300 mm), with nucleus intorted vs non intorted in A. parvimaculata n. sp., sculptured by five small keels with an axial sculpture in the interspaces, replaced by scattered microtubercles towards the last quarter of a whorl vs a protoconch devoid of sculpture in A. parvimaculata n. sp.

Figures

FIG. 14. — Alvania parvimaculata n. sp.: A, B, holotype, Tuamotu, height 1.65 mm, 1-20 m, MNHN-IM-2000-38706; C, D, paratype, height 1.65 mm; E, F, paratype, height 1.55 mm, MNHN-IM-2000-38707.

FIG. 15. — Alvania parvimaculata n. sp.: holotype, Tuamotu, height 1.65 mm, 1-20 m, MNHN-IM-2000-38706: A, shell; B, C, detail of the protoconch microscu- lpture. Scale bars: B, C, 100 μm.

FIG. 49. — Type locality of Alvania isolata (Laseron, 1956) (○, Christmas Island), and location of the stations of the “Valdivia” deep-water expedition (●) where types of Alvania denseclathrata (Thiele, 1925) (Stns 81, 95 and 104) and of Alvania proditoris (Thiele, 1925) n. comb. (Stns 81, 95 and 101) were collected.

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.