Hygromia (Hygromia) Risso, 1826

Hygromia (Hygromia) Risso, 1826

Subgenus Hygromia s.s. is characterized by a thin and translucent shell with a sharp keel at the periphery which coincides with a distinct paler band; umbilicus closed. Genitalia with two sacs of equal size, outer holding twisted dart; joint length of bursa copulatrix and its duct short; total length of flagellum, epiphallus, and penis short.

Type species: Helio cinctella Draparnaud, 1801 by subsequent designation by Herrmannsen 1847: 547.

Hygromia (Hygromia) cinctella ( Draparnaud, 1801) View in CoL

Helio cinctella Draparnaud, 1801: 87 . Type locality: ‘Lyon’. Syntype NHMW/MO/14820 ( Fig. 5A).

Description

Shell width 9.8–13.6 mm, shell height 6.7–8.5 mm, whorls 5.2–5.6. Other measurements are shown in Table 1. Shell thin and translucent; its shape sometimes roundly trochiform with a distinct paler band (50% cases) coinciding a characteristic sharp keel at the periphery. Aperture simple, lacking a lip. Umbilicus closed. Tis study recorded the largest shell diameter to date in the specimen from northern France ( 13.6 mm); shell width: 10–12 mm in Welter-Schultes (2012), 8.5–9.5 mm in Gural-Sverlova and Andrik (2023). Sculpture unevenly developed: growth lines and ridges more distinct on the upper side ( Fig. 13).

Reproductive tract of eight specimens examined agrees with those from various localities of H. cinctella (see Giusti and Manganelli 1987, Prieto and Puente 1992, Schileyko 2006, Dedov et al. 2015). Love dart small, c. 2.5 mm long, twisted ( Fig. 21A–B). Shell and genitalia features are presented in Table 2.

Distribution

Reported from across the Mediterranean and temperate Europe by Welter-Schultes (2012) and Proćków et al. (2019 and references cited therein), subsequently new records supplemented by Čejka et al. (2020) and Gural-Sverlova and Andrik (2023). Terefore, known from France, the Iberian and Italian Peninsulas, the Balkans, the British Isles, and scatered in some countries in north-western ( Belgium, the Netherlands) and Central Europe ( Austria, Germany, Switzerland, Czechia, Hungary) to Ukraine in the east. Introduced to New Zealand ( Walton 2017). In this study, 18 populations were examined (Supporting Information, Table S1; Fig. 1).

Habitat

Open areas, among low shrubs and herbs, ofen in cool and humid places such as river banks and valleys; as a synanthrope at roadsides and in disturbed environments ( Welter-Schultes 2012). In this study, it was found in similar natural and more or less human-impacted habitats.

Hygromia (Riedelia) Schileyko, 1972

Subgenus Riedelia Schileyko, 1972 has a more or less sub-globose shell of differing size with the periphery variously developed: rounded or slightly angled to slightly or clearly keeled, most ofen with a paler band. Genitalia are characterized by two sacs, the external (dart) sac more slender than the internal (accessory) sac; arched or slightly twisted dart; bursa copulatrix and its duct jointly long; total length of flagellum, epiphallus, and penis very long.

Type species: Helio limbata Draparnaud, 1805 by original designation