Alvania scuderii Villari, 2017

Amati, Bruno, Appolloni, Massimo, Giulio, Andrea Di, Scuderi, Danilo, Smriglio, Carlo & Oliverio, Marco, 2020, Revision of the Recent Alvania scabra (Philippi, 1844) complex (Mollusca, Gastropoda Rissoidae) from the Mediterranean Sea with the description of a new species, Zootaxa 4767 (3), pp. 415-458 : 440

Alvania scuderii Villari, 2017

( Figs 11 A–I; 13; 17A–C; 18G, H; Table VII)

Alvania scuderii Villari, 2017: 937 , 942, figs 1–9, 17–19

Other references.

Alvania scuderii ; Scaperrotta et al., 2019: 143, pl. IV, fig. I.

Type material. Holotype MZB 47004 . Paratype 1, same data as the holotype, MFV-ME number: 935/ 05-12-2017. Paratype 2, same data as the holotype (DS). Other paratypes, same data as the holotype, 9 lv and 14 sh, all in AV, DS and PM. Type locality: Messina, Ganzirri, Sicily, rocky bottom, 2–4 m depth.

Other material examined. Sicily: Catania, Acitrezza, 10 m depth, 5 sh (DS); Catania, Armisi, 20 m depth, 2 sh (DS); Catania, S. Giovanni Li Cuti, 4–8 m depth, 3 sh, 2 lv (DS); Linosa Is., Punta Calcarella, 36 m depth, 1 sh ( CS-PM); Linosa Is., Secchitella, 20 m depth, viii.2017, 5 sh + 2 frg ( CS-PM), 1 sh (BA), 35 m depth, 3 sh ( CS-PM); Linosa Is., Balata Piatta, 20 m depth, 4 sh ( CS-PM); Linosa Is., Faro, vi.1995, 9 sh, 35 m depth (DS). Italy: Scilla, 43–44 m depth, vii.2015, 1 sh (MO).

Distribution. Known so far only from eastern Sicily and the Sicily Strait ( Fig. 13 ). Living on Messina rocky bottom amidst algae, in 2–8 m depth (eastern Sicily); empty shells in 20–52 m depth (see also https://www.naturamediterraneo.com/forum/topic.asp?TOPIC_ID=26442—accessed 13 december 2017, as Alvania scabra ). Found sympatric with A. scabra A. sororcula and A. pizzinii n. sp. At Messina A. scabra , A. sororcula and A. scuderii are syntopic in summer (DS, unpublished), with A. scabra more abundant, and A. sororcula and A. scuderii showing slightly deeper depth ranges.

Description (data for the holotype in parentheses). Shell ( Figs 11 A–I; 17A–C) small for the genus, 1.55–2.1 (2.1 mm) mm, width 0.916–1.18 (1.18) mm, ratio H/W 1.69–1.78 (1.78), ovate-conic. Protoconch ( Figs 17B, C ) paucispiral with nucleus moderately intorted, of 1.2–1.3 (1.3) whorls, height 0.262 –0.320 (?) mm; nucleus diameter (d) 0.100 –0.120 (?) mm, first half whorl diameter (Do) 0.157 –0.205 (?) mm, maximum diameter (DM) 0.295 –0.312 (?) mm, sculpture of parallel rows of microtubercles of different shapes, sometimes fused ( Figs 17B, C ). Protoconch-teleoconch boundary well marked. Teleoconch of 2.9–3.4 (3.3) convex whorls, with suture impressed. Axial sculpture on the last whorl of 15–18 (?) slightly prosocline and sinuous ribs, plus the labial varix, narrower than the interspaces and interrupted at the base. Spiral sculpture same strength as axial, of almost equidistant cords, 8 (8) on the last whorl, with 4 (4) above the aperture and 4 (4) slightly thicker on the base. Cords II and IV starting immediately after the protoconch-teleoconch boundary; cord I appearing at 1.2–1.5 whorls (remaining thinner than others), cord III starting after 1.5–1.8 whorls (Table VII). Small, rounded tubercles at the intersections; interspaces quadrangular. Microsculpture of weak growth lines and spiral threads overall ( Fig. 17B ). Umbilical chink absent. Aperture pyriform, large, rounded ovate anteriorly, height 0.65–0.85 (0.85) mm, H/Ha ratio 2.36–2.61 (2.47), peristome continuous, outer varix modest, internally smooth. Background colouration brownish, with dark brown spiral cords, aperture and columella lighter. Operculum thin, paucispiral, with eccentric nucleus (see alsoVillari 2017). Soft parts ( Figs 18G, H ): semi-transparent whitish background with grey/dark-grey areas on both sides of body, darker on opercular area, extending at edge of sole of foot. Pale brownish median area on snout. Yellow speckles on snout, merged in short stripes on head behind and in front of eyes, forming lines along cephalic tentacles, on foot and opercular area, on propodium, and a yellow π figure under the operculum; two whitish granular masses near eyes, scattered white speckles on cephalic tentacles; 4 metapodial tentacles. (See also Villari, 2017).

Remarks. Species very homogeneous, almost no variation detected so far. Maximum size: height 2.1 mm, width 1.18 mm. Axials may be very slightly broader than the spirals, ranging 15–18 on the last whorl. See under A. scabra , A. sculptilis , A. sororcula , A. lucinae , A. josefoi and A. pizzinii n. sp. for the differences with these species.

Figures

FIGURE 11. Alvania scuderii Villari, 2017. A–C. Linosa Is. 35 m depth (Italy), height 1.69 mm (CS-PM). D–F. same locality (Italy), height 1.8 mm (CS-PM). G–I. same locality (Italy), height 1.82 mm (CS-PM).

FIGURE 13. Distribution based on the material examined and checked literature data. Red dots, Alvania scuderii Villari, 2017. Light-blue dots, Alvania pizzinii n. sp.

FIGURE 17. Alvania spp. (SEM). A–C. Alvania scuderii Villari, 2017, Linosa Is. 35 m depth (Italy), height 1.69 mm (CS-PM). A. Shell. B. Detail of the protoconch microsculpture, same specimen. C. Detail of the teleoconch microsculpture, same specimen. D–F. Alvania pizzinii n. sp. holotype, MNHN IM-2000-33933, height 2.3 mm, Levanzo Is. (Italy). D. Shell. E. Detail of the protoconch microsculpture, same specimen. F. Detail of the teleoconch microsculpture and of the subsutural ramp, same specimen. G–I. Alvania grancanariensis Segers, 1999, Maspalomas, Gran Canaria, Canary Islands (Spain) height 1.85 mm (JT, JDO). G. Shell. H. Detail of the protoconch microsculpture, same specimen. I. Detail of the teleoconch microsculpture, same specimen.

FIGURE 18. Alvania spp. drawing of external soft parts. A, B. Alvania scabra (Philippi, 1844), S. Giovanni Li Cuti, Catania, Sicily, 4 m depth (DS). C, D. Alvania scabra (Philippi, 1844), Los Escullos, Cabo de Gata, Spain, (AN29. MNHN), redrawn after a sketch by Serge Gofas (Malaga). E, F. Alvania sororcula (Granata-Grillo, 1877), S. Raineri, “Degassifica”, Messina, Sicily, 2–4 m depth (DS). G, H. Alvania scuderii Villari, 2017, Ganzirri, Messina, Sicily, 4–5 m depth (MZB).