Naticarius stercusmuscarum (Gmelin, 1791)

Huelsken, Thomas, Marek, Carina, Schreiber, Stefan, Schmidt, Iris & Mann, Michael Holl-, 2008, The Naticidae (Mollusca: Gastropoda) of Giglio Island (Tuscany, Italy): Shell characters, live animals, and a molecular analysis of egg masses, Zootaxa 1770, pp. 1-40 : 19-21

Naticarius stercusmuscarum (Gmelin, 1791) — Figs. 5A , B

+ Natica canrena sensu auct. non Linnaeus, 1767. Sabelli et al. (1990), p. 170

+ Nerita punctata Karsten, 1789 [non punctata Müller, O.F., 1776 ]. Sabelli et al. (1990), p. 170

Nerita stercusmuscarum Gmelin, J.F. 1791 . Tomus 1, pars VI, Vermes testacea. Lipsiae. in: Editio decima tertia, reformata, cura J.F. Gmelin (Ed.), Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonomis, locis. G. E. Beer, p. 3673.

+ Natica punctata (Karsten, 1789) . Hidalgo (1917), p. 490

+ Natica millepunctata Lamarck, 1822 . Weinkauff (1867), pp. 242–245; Kobelt (1901), Vol II, p. 74, pl. 51, figs. 1–9

+ Nacca punctata Risso, 1826 . Sabelli et al. (1990), p. 170

+ Natica sanguinolenta Brusina, 1865 [non sanguinolenta Deshayes, 1839 ]. Sabelli et al. (1990), p. 170

+ Natica (Naticarius) punctata (Chemnitz in Karsten, 1789). Settepassi (1972), p. 24, pls. 3, 4; Villa (1986b), pp. 134– 136

+ Naticarius punctatus (Chemnitz in Karsten, 1789). Sabelli & Spada (1980), pp. 1, 3, pl. 3, fig. 1; Schirò (1978b), p. 4, fig. 2 (first row); p. 5 fig. 1; Poppe & Goto (1991), pp. 119–120, pl. 16, figs. 21–23, Terreni (1981), p. 31

Naticarius stercusmuscarum (Gmelin, 1791) . Nordsieck (1982), p. 186, pl. 57, fig. 63.10; Riedel (1983), p. 288, pl. 98

+ Naticarius millepunctatus (Lamarck, 1822) . Barash & Danin (1992), p. 107, fig. 114

Natica (Naticarius) stercusmuscarum (Gmelin, 1791) . Demir (2002), p. 110, Gelatolo (2004), http://www.naturamediterraneo.com/forum/topic.asp?TOPIC_ID=4259, [shell was found at the beach of Isola del Giglio: listed as form „ pocopunctatus “]

Description

Shell, apex, operculum and umbilical area similar to N. hebraeus ; generally smaller in size, with a slightly more elevated spire.

Size: Up to 54.1 mm m.o.d. (off Isole Egadi, Sicily, Italy; MHC#030511.23). Specimens (n = 23) from Giglio Island: 12.2–29.8 mm (mean: 18.6 ± 1.0 mm) height; 13.0– 30.5 mm (mean: 19.6 ± 1.0 mm) width. Ratio [h/ w] = 0.95 ± 0.006. Aperture approximately 82% of shell height.

General shape: Globose with slightly elevated spire, large body whorl, relatively thin-shelled for its size, 4.25 convex, slightly tabulated whorls, adpressed at sutures [teleoconch: 3.5]. Sculpture: Same as N. hebraeus .

Shell color: Distinct perfectly rounded dots distributed regularly on whitish, cream or yellowish shell; a distinctive sparsely dotted color form known only from Giglio Island has less dots distributed irregulary over yellowish shell, sparing an uncolored band underneath the suture.

Protoconch: Uncolored, one embryonal whorls.

Aperture & outer lip: Aperture half moon-shaped, oblique, angled anteriorly, base rounded, thickened; external lip simple, sharp. Fairly thick parietal callus, covering 1/4 to 1/3 of inner lip.

Umbilical area: Same as N. hebraeus .

Operculum: Same as N. hebraeus .

Animal: Mesopodium and propodium surround shell to same width during crawling; only lower fringe of shell covered by mesopodium, tentacles whitish grey. Mesopodium of sparsely dotted color form has thin whitish lines while typical form shows distinct white dots ( Figs. 5A /B); fringe of mesopodium of typical form shows distinct white line which is absent in sparsely dotted form; color patterns of propodium and tentacles identical in both forms (whitish-grey).

Differential diagnosis: N. stercusmusarum is most easily distinguished from N. hebraeus by the distinct color pattern of the animal, but also of the shell. N. hebraeus has dark tentacles, and a dark foot with radial, irregularly, whitish to cream-colored, distributed lines, while N. stercusmuscarum has lightly colored tentacles and a dark foot showing distinct whitish to cream-colored dots of different size distributed irregularly across its surface. On the shell, N. hebraeus has irregularly arranged, blurred, brownish dots that have a tendency to coalesce into bands and/or larger blotches, while N. stercusmuscarum has distinct, brownish, well-separated dots distributed regularly over its shell. Average ratios of height to width of 58 shells of N. hebraeus is 1.01 ± 0.005 (SEM), and 0.95 ± 0.006 (SEM) for 23 shells of N. stercusmuscarum . The difference is significant in a non-parametric two-tailed t-test including 23 pairs (p-value <0.0001). However, despite the statistical significance of the differences in ratio of width to height, individual specimens from Giglio Island cannot be identified unambiguously based on size alone, due to the overlapping size distribution.

The sparsely dotted form of N. stercusmuscarum has significantly fewer dots than the typical form. The dots are not as regularly spaced as in the typical form, and may touch each other to form short streaks. The mesopodium of the sparsely dotted form has thin, short, whitish lines while that of the typical N. stercusmuscarum has distinct dots; color patterns of the propodium and tentacles are indistinguishable. A distinct white fringe which surrounds the mesopodium of the typical N. stercusmuscarum is absent in the sparsely dotted form. Molecular comparison between these two color forms of N. stercusmuscarum was complicated by the fact that only tissue of one partly decomposed specimen of the sparsly dotted form of N. stercusmuscarum was available. The data obtained from that tissue did not show differences in a partial 18S rRNA gene (ca. 350 bp). However, the analyzed fragment lies in a well conserved region of the 18S gene and may not be sufficiently informative to differentiate closely related species. A specimen of the sparsely dotted form of N. stercusmuscarum observed in an aquarium fed exclusively on other naticids and ignored Venus mussels, even when starved for several days. None of several specimens of the typical form of N. stercusmuscarum showed such a behavior. Additional molecular analysis will have to be performed to verify that the sparsely dotted form is indeed a distinct species.

Geographical distribution

Giglio Island: Campese Bay (1), P. del Faraglione (2), Cala dell´Allume (4), Pt. del Morto, (6). The sparsely dotted form of N. stercusmuscarum was found exclusively in the Bay of Campese ( Figure 4 ). General distribution: Contrary to many publications ( Hidalgo 1917, Settepassi 1972, Schirò 1977), this species is probably strictly Mediterranean, widespread from the Strait of Gibraltar to the Aegean Sea with reports from the Sea of Marmara and from the Black Sea (Demir 2002).

Figures

FIGURE 4: Schematic map of Giglo Island, Grosseto County, Tuscany, Italy (42 ° 21.000 ´´ N 10 ° 54.000 ´´ E), including all collecting sites with naticid occurence: 1, Campese Bay; 2, Pt. del Faraglione; 3, Pt. delle Secche; 4, Cala dell´Allume; 5, Pt. del Corvo; 6, Pt. del Morto; 7, Pt. della Campana; 8, Cannelle Bay; 9,´Swiss House´; 10, Pt. del Fenaio. Pure shallow sandy sites are Campese Bay, Pt. del Faraglione, and Canelle Bay, while the remaining sites are bluffs with rocks, coarse sand flats, and sea weeds. The circular charts show the material (A, living specimens; E, egg masses; S, empty shells) collected at each site in a qualitative manner. N. dillwynii is distributed widest. Collected egg masses listed here were included in the molecular analysis.

FIGURE 5: A, Sparsely dotted form of Naticarius stercusmuscarum (Gmelin, 1791); B, Naticarius stercusmuscarum (Gmelin, 1791). All specimens are shown in four standardized views (dorsal, apertural, apical, umbilical) as well as alive. The pictures of living specimens were taken in an aquarium with a black bottom. Scale bars represent 0.5 cm.