Black slug (Arion ater) (Steve Orridge)

Slugs and snails (Gastropoda)

About slugs and snails

Snails and slugs are molluscs in the large class of Gastropoda, or gastropods, which includes a large array of land, marine and freshwater species. Snails evolved first, developing a single coiled shell into which they can withdraw, and this feature is characteristic of all land snails, but in slugs has been much reduced (semi-slugs) or completely internalised to a small plate or a few granules (slugs). 

Land snails and slugs in the British Isles belong to two subclasses of the Gastropoda class:

  • the Prosobranchia (only 2 land species, the other 50 (approx) species being aquatic). These have an operculum, which is a horny lid carried on the snail’s foot and which seals the mouth of the shell when the snail is withdrawn. These  species have separate sexes.
  • the Pulmonata (about 90 species of land snails and over 36 species of slugs) which are characterised by having a lung in their mantle cavity. These species are hermaphrodite, most being outcrossers (mating with other individuals) but some, at least some of the time, being self-fertilising and, in some cases, losing part of the male reproductive system.

Snails and slugs have a range and diversity of diets, many being herbivores and/or detritivores and many being carnivores, predating other species. They in their turn provide a valuable food resource for other animals and birds.

An entertaining and informative short video by an expert on how and why slugs evolved via semi-slugs from snails.

‘Slimy, Sticky and Unloved\; Slugs in Britain.’ A very good, enjoyable and informative FSC webinar on slugs by Imogen Cavadino. 

Slugs and snails in the High Peak

White-lipped Snail, Upper Lathkill Dale 20/07/21 (Bill Williams)

For these buttons with the solid borders to work properly you will need to be registered and logged into iNaturalist. This is a free and extremely useful app. See our ‘How to record wildlife’ page for more information and tips on how to use it.

Takes you to the up-to-date list and photo galleries of all slug and snail observations within the High Peak area, as recorded on iNaturalist

Takes you to the up-to-date list and photo galleries of all slug and snail observations within the ‘Buxton polygon’ area, as recorded on iNaturalist and collected by the Buxton Biodiversity Recording Group project

Doorsnail (Clausiliidae spp, poss. Clausilia bidentata) Taddington 06/11/21 (R Furness)
Doorsnail (Clausiliidae spp, poss. Clausilia bidentata) Taddington 06/11/21 (R Furness)
Doorsnail (Clausiliidae spp, poss. Clausilia bidentata) Taddington 06/11/21 (R Furness)

Doorsnails, of the Clausiliidae order, are unusual in having shells that are sinistral (the shell is coiled anticlockwise when viewed from above, and the mouth of the shell is on the left when viewed from the front). Their shells are also notably long and narrow, as shown in the photos. Only this order and 2 species of Vertigo (the Vertiginidae order) are naturally coiled sinistrally. The rest are dextral, except in less than 1 in 100,000 specimens.

Tree Slug (Lehmannia marginata), (Steve Orridge)

Identifying slugs and snails

Slugs of Britain and Ireland: Understanding, Identification and Control

Ben Rowson, James Turner, Roy Anderson and Bill Symondson

FSC

Summary

Land Snails in the British Isles

Robert Cameron and Gordon Riley (illustrations)

FSC

Summary

Slugs and Snails: Book 133 in The New Naturalist Library

Robert Cameron

Collins

A fairly recent (2016) addition to the classic Collins series. Relatively expensive in hardback, but knowledgeable and very informative guide to the natural history of this fascinating class of animals.

Information and guidance

Website name and link

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