Alvania sculptilis

Alvania sculptilis (Monterosato, 1877)

(Figs 4 A–O; 5A–O; 8; 15D–I; Table III)

Rissoa sculptilis Monterosato, 1877: 35, pl. III, fig. 6 (two drawings) not Alvania sculptilis (May, 1920) (Merelina) secondary homonymy (Criscione & Ponder, 2011; Bouchet, 2011)

Alvania scabra — van Aartsen et al., 1984: 24 (non Philippi, 1844)

Alvania oranica — Gofas et al., 2011: 183; Gofas, 1990: 114 (non Pallary, 1900)

Other references.

Alvania sculptilis; van Aartsen, 1982: 5, 6, 6 unnumbered figs; Amati & Oliverio, 1985: 34, fig. 3; Gofas, 1990: 130, fig. 58; Tringali, 2001: 210, figs 6a–6c,7, 8a–8b; Giannuzzi Savelli et al., 2002: 109, fig. 443; Agamennone & Micali, 2009: 6, fig. 2; Oliver & Templado, 2009: 61, 63, figs 20–22, 25; Gofas et al., 2011: 183, 3 unnumbered figs; Perna, 2013: 64, 4 unnumbered figs; Appolloni et al., 2018: 46, figs 16C, D; Scaperrotta et al., 2019: 143, pl. IV, fig. L.

Type material. Rissoa sculptilis (Monterosato, 1877) 3 syntypes (numbered 1, 2, 3) (MCZR-M-22162/S, Monterosato coll. ex Joly coll.) (Figs 3 A–C), type locality: Algiers, Algeria.

Other material examined. Morocco: Al Hoceima, beached, 95 sh (CS-PM); Cala Iris, 1 sh (MO); Chafarinas Islands (N African Mediterranean), beached, 20 sh (JT, JDO). Algeria: Algiers, 1 sh (MCZR-M-22250, Monterosato coll. ex Joly coll., as Rissoa watsoni? Schw.); Rada of Algiers, 70-90 m depth 1 sh (IN-M 260A). Spain: Granada, Punta de la Mona, Almuñecar, 7 sh (JT, JDO); Marina del Este, Almuñecar, rocks 36°43.7’N 03°43.5’W, photophylous algae 1–3 m depth, x.1999, 39 sh (SG.B114); Malága, Marbella, 2 sh. (BA); Malága, fishing darsena 36°42.63’N 04°25.36’W dock wall 0–1 m depth, iv.2018, 1 sh. (SG- J.A. Caballero coll.); Malága, Calahonda 36°29.4’N 04°41.8’W, rocks and algae, low tide, 08.x.2006, 7 lv (SG); Benalmádena-Costa, breakwater rocks 1–5 m depth 36°35.3’N 04°31.7’W, vi.2003, 8 sh (SG.AN62), 20.08.2006, 14 lv (SG); Benalmádena-Costa, beached 36°35.3’N 04°31.7’W, 3 sh (SG); Cadiz, Getares, Algeciras beached, viii.1995,>200 sh (IN), 2 sh (DS); Cadiz, Getares, Punta Carnero beached, 1988, 76 sh (IN); Cadiz, Getares Nord, Algeciras, beached, ix.1987,>250 sh (IN); Cadiz, Getares, 3–6 m depth 1985 9 sh (IN-M 207E); Algeciras (Gibraltar Strait), beached, 35 sh (JT, JDO); Gibraltar Strait, Ceuta Nord, Benzù, 35°55.0’N 05°22.5’W infralittoral 0–4 m depth, v.1986, 4 sh (Bouchet, Gofas & Lozouet leg., MNHN); Gibraltar Strait, Ceuta Sud, Anse Sarchal 35°53.4’N 05°17.8’W infralittoral, 0–3 m depth, v.1986, 1 sh (Bouchet, Gofas & Lozouet leg., MNHN); Gibraltar Strait, Ceuta Sud, Pta del Desnarigado 35°53.6’N 05°16.8’W plongée 16–20 m depth, vi.1986, 7 sh (LE 136 Bouchet, Gofas & Lozouet leg. MNHN); Tarifa, 8.ix.1985, 6 sh (BA); Balearic Islands: Colonian Sant’Jordi (Majorca Is.), 0.50 m depth, Caulerpa, 3 sh (CS-PM);

Distribution. A. sculptilis is restricted to the westernmost Mediterranean, where it is locally common (southern Spain, Morocco, Algeria, and Tunisia; Jendouba, Tabarka, only photograph of a specimen, Natural History Museum Rotterdam, 2019) (Fig. 8). Found amidst photophylous algae in Andalucia (Gofas et al. 2011; I. Nofroni pers. comm.), Morocco (Tringali 2001) in 1–10 m depth; empty shells in 0–90 m depth. Found sympatric with A. scabra and A. josefoi.

Description. Shell (Figs 4 A–O; 5A–O; 15D–I) small for the genus, height 1.55–2.42 mm, width 0.91–1.4 mm, H/W ratio 1.607 –1.967, ovate-conical. Protoconch (Figs 15E, H) paucispiral with nucleus moderately intorted, of 1.2–1.5 whorls, height 0.275 –0.325 mm, nucleus diameter (d) 0.075 –0.133 mm, first half whorl diameter (Do) 0.150 –0.250 mm, maximum diameter (DM) 0.275 –0.362 mm; sculpture of a dozen parallel rows of rounded to broadly triangular microtubercles, sometimes fused, and occasional spiral threads in the interspaces (Figs 15E, H). Protoconch-teleoconch boundary well marked. Teleoconch of 3–3.8 convex, slightly angled whorls, with suture impressed. Axial sculpture on the last whorl present or absent, of 10–20 orthocline or very slightly opisthocline ribs, plus the labial varix, narrower than the interspaces, gradually vanishing at the base. Spiral sculpture finer than the axial, of equidistant cords, 7–10 on the last whorl, with 3–5 above the aperture and 4–5 on the base, 2–3 on the penultimate whorl. Wide subsutural ramp devoid of spirals. Cords II, IV and V starting immediately after the protoconch-teleoconch boundary; cord III starting as a cordlet after 2.2 whorls, gradually yet rapidly turning into a cord; cord I appearing at 1.2–2.5 whorls (Table III), (or cords II and IV starting after the protoconch-teleoconch boundary; cord III appearing after 0.25–2 whorls; cord I starting after 1.2–2.5 whorl; cord V not starting). The casual examination of 41 shells showed, after the protoconch-teleoconch boundary, 3 spiral cords on 13 specimens and 2 spiral cords on 28 specimens. Small, rounded tubercles at the intersections; interspaces quadrangular. Microsculpture of growth lines and spiral threads on the whole surface (Figs 15F, I). Umbilical chink present or absent. Aperture pyriform, small, height 0.66–0.96 mm, H/Ha ratio 2.235–2.63, peristome continuous, outer varix modest, internally smooth. Colouration translucent whitish-yellowish, with quadrangular subsutural brown blotches; periphery and median columellar area whitish. Operculum typical for the genus, thin, corneous, paucispiral with eccentric nucleus. Soft parts unknown.

Remarks (See also Table III and Figs 4 A–O; 5A–O; 15D–I). A. sculptilis is morphologically more variable than previously suggested, even within the same population (Figs 5 A–O), in size, proportions, outline and in the strength and disposition of sculpture. In most specimens the axial sculpture is lacking or very weak (often present only on the first teleoconch whorls). The tubercles at the intersections are variably evident, but very rarely spinose.

Gofas et al. (2011: 183) considered A. oranica as a synonym of A. sculptilis, differing from the closely related A. scabra in its 3 spiral cords. Actually, A. sculptilis may also have 2 spirals on the first whorl and up to 5 above the aperture.

Tringali (2001: 209) considered A. sculptilis and A. scabra easily diagnosable in the western Mediterranean based on the lack of the fourth abapical spiral cord in A. sculptilis and the protoconch with a more confused sculpture in A. sculptilis (vs more dome-shaped and with more regular rows of microtubercles in A. scabra). Tringali (2001: 210, figs 6–8) stressed the variability of A. sculptilis, with shells showing axial and spiral sculpture of the same strength, others with axials only on the first whorls (the last dominated by spirals), and finally shells almost devoid of axial sculpture. Noteworthy, A. scabra shows almost the same range of variation (Fig. 1N).

Gofas et al. (2011: 183) considered the status of A. sculptilis vs A. scabra as unsettled, not excluding the possibility of a single very variable species. Conversely, Agamennone & Micali (2009: 4) considered the morphological difference and the geographic ‘separation’ (albeit they are sympatric in the Western Mediterranean) as sufficient to separate the two species.

TABLE III. Measurements of teleoconch and protoconch of Alvania sculptilis in mm, with range, mean and standard deviation. 1 = syntype numbered 1; 2 and 3 = syntypes numbered 2–3; 4–7, 9–12 = Getares North; 8 = Algiers; 13 = Getares 3-6 m depth; 14, 15 = Getares viii.95. *6: Axial ribs present only on the approximately last half whorl.

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TABLE III. (Continued)

Rissoa (Alvinia) conspicua Pallary, 1900 ex Monterosato, is a nomen nudum (“close to R. fischeri, but distinct”; Pallary, 1900; 1920). A specimen from Arzew, Oran (Algeria), one of the localities listed by Pallary, was found in the Monterosato collection (MCZR-M-30061). Albeit not a fresh shell, it clearly belongs to A. sculptilis (Figs 4 G–I).

Alvania sculptilis (May, 1920) [Merelina sculptilis May, 1920: 62, pl. XV, fig. 15; Criscione & Ponder 2011] (Fig. 4P) is a junior secondary homonym of Alvania sculptilis (Monterosato, 1877). However, as already commented by Bouchet (2011), these two species may prove to belong to different genera when a robust phylogeny of Alvania s.l. becomes available. We thus agree that, for the time being, it is advisable to keep using the invalid name Alvania sculptilis (May, 1920) for the Australian species. See under A. scabra for the differences with this species.

A. sculptilis differs from A. sororcula by the axial riblets on the last whorl (10–20 when present in A. sculptilis vs 25–29 in A. sororcula), and the teleoconch spiral microsculpture (spaced threadlets, more closely set only those on the spiral cords in A. sculptilis vs weaker and more spaced in A. sororcula).

A. sculptilis differs from A. lucinae by the size (H 2.42 in A. sculptilis vs 1.95 mm in A. lucinae); the tubercles at the intersections (rounded nodulose, in A. sculptilis vs spinose or almost spinose in A. lucinae); the spiral cords (all the same strength in A. sculptilis vs cord III more protruding in A. lucinae).

A. sculptilis differs from A. josefoi by the different teleoconch microsculpture (Figs 15E, F; H, I vs 16H, I) and the colouration (whitish-yellowish with subsutural blotches, and periphery and median columellar area whitish in A. sculptilis vs monochrome white, with the typical brown subsutural blotch before the varix in A. josefoi).

A. sculptilis differs from A. scuderii by the axial riblets on the last whorl (10–20, when present in A. sculptilis vs 15–18 in A. scuderii); the spiral cords above the aperture (variable 3–5 cords in A. sculptilis vs always 4 cords in A. scuderii); the colouration (translucent yellowish-whitish, with darker spiral band at the base and quadrangular subsutural brown blotches in A. sculptilis vs brownish background with dark-brown spirals in A. scuderii).

Some specimens of A. sculptilis with a slender, robust shell found along the southern Spanish coasts (Getares, Algeciras) are similar to A. pizzinii n. sp., but differ by their more robust and slender shell, the wider subsutural ramp and the visible umbilical chink.