Slugs and Snails

     

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    Introduction

    Slugs and snails are molluscs, a group that also includes Octopus, Squid and Cuttlefish, and one of the most successful invertebrate groups to have evolved. Most mollusc species are found in oceans but a few have adapted to live in freshwater and some can live on dry land. These species move by secreting mucus to lubricate their path but this results in the loss of water and all are vulnerable to dessication. To avoid this they either live in damp habitats or retreat into their shells during dryer weather.

    Around 100 snail species and 25 slug species have been recorded in Leicestershire and Rutland (VC55). Others are likely to be found as some species are expanding their range and may appear in our area.

    Recording

    Molluscs are not generally well recorded so all records are gratefully received. Perhaps its the lack of popular field guides or maybe they lack the appeal of some other groups, but molluscs are frequently encountered and many can be identified from a reasonable photo. There are only around 130 known species in VC55, divided into slugs, terrestrial snails and aquatic snails, so it is a group that you can become familiar with fairly quickly and learn to identify many of the larger and more common species without too much difficulty. As with all groups there are some trickier species and a few of the snails are very small (1-2mm) and really need a microscope to identify them, but for the majority a good photo, or even better several photos, should be enough to get an ID. You can submit photos to NatureSpot that you want help with to identify - just select '? unknown species' from the drop down menu.

    The VC55 County Coordinator for molluscs is David Nicholls and VC55 recorders are welcome to send photos or samples to him for ID help.

    Nationally the Conchological Society of Great Britain & Northern Ireland (see link above) collects mollusc records for the whole of the UK and aims to collate information about their ecology and distribution.

    As with all records, any submissions you make to NatureSpot will be automatically forwarded to both local and national recording schemes.

    Identification tips

    Snails - most snails can be identified from their shells which offers opportunities for finding evidence of a species after it has died. It is often easier to find empty shells than the live animal and it is generally acceptable to record the species based on finding the shell. So if you come across shells whilst out and about do collect them and note where you found them. Aquatic snail shells can often be found amongst flood debris, or on the exposed margins of a water body during a drought. Again photos are invaluable to help provide evidence to support your record and/or to help identify the species.

    Slugs - these can be harder to identify and there are several groups of closely related species that can be difficult to tell apart visually. A few slug species are usually recorded as an aggregate, such as Arion ater agg., to get round the identification problem. However most can be identified to species with a bit of practice.

    Leicestershire and Rutland Resources

    Keys

    Online

    Printed

    • Slugs of Britain and Ireland (Field Studies Council - AIDGAP) - a superb up to date book, full of images and drawings, with a key, species accounts and distribution maps. Highly recommended.
    • Land Snails in the British Isles (Field Studies Council AIDGAP) - an excellent key which is easy to use with many illustrations.
    • Freshwater Bivalves of Britain Ireland (Field Studies Council AIDGAP) - essential if you want to learn to identify this group.

    Other useful websites and publications

    Online

    Printed

    • Slugs and Snails, Robert Cameron (New Naturalist) - published in 2016 this is a comprehensive account of the natural history of this group.
    • A Field Guide to the Land Snails of Britain and North-West Europe (Collins Field Guide) - the only 'popular' field guide around for this group. Includes slugs and has colour plates, but a little dated and not totally accurate.
    • The Land and Freshwater Molluscs of Suffolk, Ian Killeen (Suffolk Naturalist's Society).

    If you know of other websites or books that you would recommend, do let us know: info@naturespot.co.uk

    Photographs to support records

    Here are a few tips of the features it helps to photograph. Also add a note to your record about size - this is often crucial information.

    Slugs

    • a dorsal or oblique view of the whole animal - showing the keel if it has one and ideally with the head/tentacles extended
    • a side view from the right side showing the breathing pore
    • the sole (some have a central dark stripe or dark edges)
    • whilst not easily photographed, the colour of the mucus can be important so stroke the slug and examine the slime on your finger!

    Snails

    • a dorsal or oblique view of the whole animal - showing the number of whorls and ideally with the head/tentacles extended
    • the underside - showing the mouth opening and the umbilicus (the hole in the centre)
    • a side view - the height of the shell is often a key feature
    • some aquatic snails have an operculum - a shell-lid that closes over the mouth when they withdraw inside

    You can submit up to four photos with a record. You don't need to resize them, the computer will do this automatically as it uploads a copy.