This list of the non-marine molluscs of Ireland comprises 169 species of non-marine molluscs that have been recorded as part of the fauna of Ireland. Ireland is an island in the northeastern Atlantic. It consists of the Republic of Ireland, also known simply as Ireland (or in the Irish language Éire), and Northern Ireland, which is part of the United Kingdom. Included in the list are terrestrial gastropods (land snails and slugs) and freshwater and brackish water gastropods and bivalves (mussels and clams). Molluscs that are fully adapted to live in the sea are not included here, except for one marine pulmonate snail that breathes air. Some species of gastropods listed (e.g. Peringia ulvae) live in habitats that are intermediate between freshwater and saltwater. Others live in habitats that are intermediate between land and saltwater. Both of these kinds of species are often also included in marine faunal lists. In addition to the species that live naturally outdoors in Ireland, there are at least 2 aquatic gastropod species which live only in artificially-heated indoor environments such as aquaria in greenhouses. These are known as "hothouse aliens", and in this list they are not counted as part of the total fauna. The mollusc fauna of the island of Ireland has not been as thoroughly researched as that of the island of Great Britain, and therefore it is possible that some uncommon and local species (whether native or introduced) may, as yet, have been overlooked. Even so, it seems that the non-marine molluscan fauna of Ireland is a smaller fauna than that of Great Britain. The following table shows a summary of species numbers. It is not always easy to define which species are aquatic and which are terrestrial, as some species such as Galba truncatula are virtually amphibious. It also can be difficult to determine which species are introduced, as some introductions are quite ancient, for example from the Paleolithic. Those species that do not have a shell usually do not leave an archaeological or fossil record, and therefore it is especially difficult to determine whether they are native or introduced.

Conservation

Species protected by EU Habitats Directive include: Geomalacus maculosus (annex II and IV), Vertigo angustior, Vertigo geyeri, Vertigo moulinsiana (annex II) and Margaritifera margaritifera (annex II and V). Two species have been protected by the Wildlife Act of 1976 since 1990: Geomalacus maculosus and Margaritifera margaritifera. They were added by regulation SI 112/1990. A recent regional red list has been published of the non-marine molluscs of Ireland by Byrne et al. (2009). In this publication, the threat status of 150 native species was evaluated using IUCN regional guidelines. Of these species, two are considered to be regionally extinct, five critically endangered, fourteen endangered, twenty-six vulnerable, six near threatened, and the rest of least concern, or data deficient. This publication has sparked some media discussion about molluscan conservation in Ireland, including articles written in the Irish Times.

Regional Red List of Irish non-marine molluscs

The following species have been assigned threat categories or were considered regionally extinct on the island of Ireland in 2009: Regionally extinct (RE) Helicigona lapicida (Linnaeus, 1758); Omphiscola glabra (O.F. Müller, 1774) – listed as extinct in the red list, but rediscovered in 2009. Critically Endangered (CR) Pisidium conventus Clessin, 1877 Pomatias elegans (O.F. Müller, 1774) Margaritifera margaritifera (Linnaeus, 1758) Truncatella subcylindrica (Linnaeus, 1767) Margaritifera durrovensis Philips, 1928 Endangered (EN) Gyraulus laevis (Alder, 1838) Pisidium pulchellum Jenyns, 1832 Hydrobia acuta neglecta (Muus, 1963) Pupilla muscorum (Linnaeus, 1758) Mercuria cf. similis (Draparnaud, 1805) Quickella arenaria (Potiez & Michaud, 1835) Merdigera obscura (O.F. Müller, 1774) Spermodea lamellata (Jeffreys, 1830) Myxas glutinosa (O.F. Müller, 1774) Succinella oblonga Draparnaud, 1801 Pisidium moitessierianum Paladilhe, 1866 Vertigo moulinsiana (Dupuy, 1849) Pisidium pseudosphaerium Schlesch, 1947 Vertigo pusilla O.F. Müller, 1774 Vulnerable (VU) Acicula fusca (Montagu, 1803) Pisidium lilljeborgii Clessin, 1866 Anisus vortex (Linnaeus, 1758) Radix auricularia (Linnaeus, 1758) Anodonta anatina (Linnaeus, 1758) Sphaerium nucleus (Studer, 1820) Anodonta cygnea (Linnaeus, 1758) Tandonia rustica (Millet, 1843) Aplexa hypnorum (Linnaeus, 1758) Testacella haliotidea Draparnaud, 1801 Arianta arbustorum (Linnaeus, 1758) Vallonia pulchella (O.F. Müller, 1774) Balea perversa (Linnaeus, 1758) Ventrosia ventrosa (Montagu, 1803) Cecilioides acicula (O.F. Müller, 1774) Vertigo angustior Jeffreys, 1830 Cochlodina laminata (Montagu, 1803) Vertigo antivertigo (Draparnaud, 1801) Helicella itala (Linnaeus, 1758) Vertigo geyeri Lindholm, 1925 Leiostyla anglica (A. Férussac, 1821) Vertigo lilljeborgi (Westerlund, 1871) Limax cinereoniger Wolf, 1803 Zenobiella subrufescens (J.S. Miller, 1822) Musculium lacustre (O.F. Müller, 1774) Zonitoides excavatus (Alder, 1830)

Systematic list

The list is arranged by biological affinity, rather than being alphabetical by family. A number of species are listed with subspecies, in cases where there are well-recognized subspecies in different parts of Europe. For some species a synonym is given, where the species may perhaps be better known under another name. An attempt has been made to label the families as aquatic, terrestrial or intermediate, and an indication is given where it is thought that the species is introduced. Species are considered to be native, unless otherwise indicated; that information is mostly taken from Kerney, and Rowson et al. The status and taxonomy of freshwater gastropods has been updated according to Rowson et al. (2021).

Gastropoda

The following gastropods are pulmonates:

Bivalvia

List of "hothouse alien" species

These freshwater species are not truly part of the fauna, because they do not live in the wild. They are tropical, and thus are incapable of surviving in the wild in Ireland; instead they have established themselves as uninvited inhabitants of aquaria within greenhouses, and similar artificially-heated aquatic habitats.