Cernuella (Cernuella), (CERNUELLA)

Hausdorf, Bernhard & Sauer, Jan, 2009, Revision of the Helicellinae of Crete (Gastropoda: Hygromiidae), Zoological Journal of the Linnean Society 157 (2), pp. 373-419 : 414-416

CERNUELLA (CERNUELLA) SCHLÜTER, 1838

Diagnosis: Cernuella s.s. is characterized by three small muscles (‘frenula’) that connect the base of the penial papilla with the penis wall (see Manganelli & Giusti, 1988).

CERNUELLA (CERNUELLA) VIRGATA ( DA COSTA, 1778) ( FIGS 12I , 14F , 15A, B;

TABLES 1, 15, AND 20)

Cochlea Virgata Da Costa, 1778: 79 , pl. 4, fig. 7. Locus typicus: ‘Heddington heath, in Oxfordshire’; ‘Hampshire’; ‘Cornwall’; ‘Newmarket heath, in Cambridgeshire’, United Kingdom.

Helix (Xerophila) variegata – Westerlund & Blanc, 1879: 70.

Helix (Xerophila) eugoniostoma forma major Westerlund & Blanc, 1879: 73. Locus typicus: ‘aux environs de Candie’, Greece.

Helix (Xerophila) variabilis – Martens, 1889: 187.

Cernuella virgata – Sumner, 1983: 63.

Cernuella (Cernuella) virgata – Frank, 1988: 87.

Cernuella virgata – Vardinoyannis & Mylonas, 1988: 139.

Cernuella jonica – Vardinoyannis & Mylonas, 1988: 139.

Cernuella ‘ virgata-ionica ’ – Vardinoyannis, 1994: 84, 87, 128, map 40.

Diagnosis: Cernuella virgata is characterized by a depressed conical, finely and irregularly ribbed, shell with an often reddish internal rib in the aperture, and a moderately wide, slightly eccentric umbilicus.

Shell ( Fig. 15A, B ; Table 1): Depressed conical; with 4.5–5.5 convex whorls; teleoconch with irregular fine ribs that usually become weaker on the body whorl and irregular impressions (also on the top); whitish, with or without brown bands that might be fused or break up into spots; body whorl rounded or with a blunt edge at the beginning; aperture almost circular; upper insertion of the peristome hardly or distinctly descending; peristome sharp, not expanded, with a whitish or reddish internal rib; umbilicus narrow or moderately wide, slightly eccentric, not obscured by the columellar edge.

Abbreviations: da, dart apparatus; epd, epiphallus distal of the insertion of the penial retractor; epp, epiphallus proximal of the insertion of the penial retractor; fl, flagellum; p, penis; vda, vagina up to the base of the dart apparatus; vgm, vagina up to the glandulae mucosae; vt, total length of the vagina.

Genitalia ( Fig. 14F ; Table 15 and 20): See diagnosis of the genus. A more detailed description of the genitalia has been given by Hausdorf (1988) and Manganelli & Giusti (1988).

Remarks: Cernuella virgata differs from Xerocrassa cretica in the more rapidly increasing whorls, the irregular ribbing, the more numerous irregular impressions on the top, the often reddish internal rib in the aperture, and the frequently more eccentric umbilicus. Forms with a reddish internal rib can be easily identified. However, there are also forms with a whitish internal rib.

Often Cernuella cisalpina (Rossmässler, 1837) [= Cernuella jonica ( Mousson, 1854) ] is distinguished from C. virgata as a separate species ( Kerney et al., 1983; Falkner, 1990; Giusti et al., 1995). Typical C. cisalpina differ from C. virgata in the smaller (see Table 1), more depressed, and more strongly ribbed shell, with a wider umbilicus. We consider C. cisalpina a form of the highly variable C. virgata , because there are no anatomical differences, and because there are various combinations of shell characters and all intermediate forms can be found. Moreover, it is worth mentioning that there are also large, smooth forms and smaller, ribbed forms in Trochoidea pyramidata , where the forms have not been considered distinct species.

Distribution ( Fig. 12I ): Cernuella virgata is widespread in the Mediterranean region, Western Europe, and the Macaronesian Islands. It probably originated in the western Mediterranean region, and was perhaps introduced into the eastern Mediterranean region only by man.

Figures

Figure 12. Distribution of Helicellinae on Crete (UTM grid, 10-km squares): •, records for which vouchers have been checked; -, records from the literature. A, Trochoidea pyramidata (Draparnaud, 1805). B, Xeropicta krynickii (Krynicki, 1833). C, Pseudoxerophila bathytera (Westerlund & Blanc, 1879). D, Pseudoxerophila oertzeni (Maltzan, 1887). E, Xeromunda candiota (L. Pfeiffer, 1849). F, Xerotricha apicina (Lamarck, 1822). G, Xerotricha conspurcata (Draparnaud, 1801). H, Microxeromagna lowei (Potiez & Michaud, 1835). I, Cernuella (Cernuella) virgata (Da Costa, 1778).

Figure 14. Helicellinae from Crete: genitalia. Scale bar: 1 mm. A, Pseudoxerophila oertzeni (Maltzan, 1887), Omalos (ZMH 29719). B, Xeromunda candiota (L. Pfeiffer, 1849), Drapanos, 4 km towards Kokkinio Chorio (ZMH 36255). C, Xerotricha apicina (Lamarck, 1822), Corsica, Cardo (from Giusti & Manganelli, 1989: fig. 4B). D, Xerotricha conspurcata (Draparnaud, 1801), Sardinia, Valletta Logulentu (from Giusti & Manganelli, 1989: fig. 2B). E, Microxeromagna lowei (Potiez & Michaud, 1835), Greece, Lakonia, Sgardelianika near Neapoli (from Hausdorf, 1990b: fig. 1). F, Cernuella (Cernuella) virgata (Da Costa, 1778), Roustika, 0.2 km towards Rethimnon (ZMH 36110).

Figure 15. Helicellinae from Crete: shells. A, Cernuella (Cernuella) virgata (Da Costa, 1778), Roustika, 0.2 km towards Rethimnon (ZMH 36110). B, Cernuella (Cernuella) virgata (Da Costa, 1778) (‘cisalpina’), Kato Zakros (ZMH 27083). Scale bar: 10 mm.