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Alien snails

February 5, 2009

This week non-native species of land snail have been on my mind a lot, as I was analysing an archaeological asssemblage which contained some Cornu aspersum Müller 1774, a species usually described as having been introduced back in Roman times.  Walking in Yeovil this morning, I spotted a shell I had not seen locally before. It was from the snail Hygromia cinctella Draparnaud 1801, another introduced species. The sources I consulted (Kerney and Cameron 1979, Davies 2008*) both agree that it first appeared in Devon around 1950, and Kerney and Cameron describe its distribution as “SE France, extending up the Rhône valley into Switzerland (Geneva basin); also near the Atlantic in SW France” (Kerney and Cameron 1979: 190-191)

Hygromia cinctella

Hygromia cinctella

Snails are, you will of course realise, rather slow movers, so how do these species come to be present in the UK, and spread once they get here? Passive dispersal is the most likely answer. In the case of H. cinctella, and the much older introduction C. aspersum, the snails have probably been unintentionally moved by humans, perhaps in soil or produce. Davies (2008: 16-17) lists a number of introductions to the British Isles since the Bronze Age.

Here are some more pictures of Yeovil’s alien snail. I shall be keeping a good eye out for more specimens.

Hygromia cinctella

Hygromia cinctella

H. cinctella has a sharply keeled shell, with a thin white band

H. cinctella has a sharply keeled shell, with a thin white band

References:
Davies, P., 2008: Snails: Archaeology and Landscape Change (Oxford: Oxbow)

Kerney, M.P., and Cameron, R.A.D., 1979: A Field Guide to the Land Snails of Britain and North-West Europe. (London: Collins)

*this asterisk doesn’t refer to any special meaning, it’s just there to stop WordPress rendering 2008close parenthesis as 2008) !

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8 Comments leave one →
  1. Paul Davies permalink
    March 11, 2009 9:57 am

    The National Museum of Wales recently carried out an online survey to see how far this species had now spread through England and Wales. the results can be found online at: http://www.museumwales.ac.uk/en/1756/ where a distribution map is avaliable. As will be seen, it has spread considerably (in geographic terms) in a relatively short period of time. The species can often be found on concrete walls, so it is not difficult to imagine it spreading, for example, via construction materials along the road or rail networks.

  2. matthewlaw permalink*
    March 11, 2009 5:43 pm

    Hi Paul,

    Thanks so much for drawing to attention to that. I think it’s a great scheme and it’s really good that so many people took part. I wasn’t aware that there’s an association with concrete, do you think that’s because of the lime content?

    Oh, in case you’re wondering about the odd little footnote by the reference to your book, at the time I wrote this post WordPress automatically rendered “2008)” as 200 with a smiley face wearing sunglasses, but that seems to have changed now, with the result that it looks a little like I have a dislike of seeing 2008 in brackets!

  3. Paul Davies permalink
    March 17, 2009 2:43 pm

    Hi again Matthew. Yes I’m sure it’s the lime content. It’s particulalry telling that many of the larger helicid snails can be found concentrated around concrete fencing posts in otherwise geologically acidic areas. There are a few examples given in my book (Chapter 2 somewhere) of studies showing how snails obtain calcium when it is lacking from soil/water. The examples include rasping other shells (re-cycling of lime) and I’m sure rasping of concrete and other lime construction materials is also practiced.

  4. matthewlaw permalink*
    March 17, 2009 5:45 pm

    Hi Paul,

    I remember reading those with interest, as I was recently idly wondering how gastropod rasping would effect the appearance of archaeological bone. Simon Mays mentions it in passing as a taphonomic factor on human bone from marine contexts in an article in the most recent (I think) Environmental Archaeology. Have you ever come across any references to gastropods rasping bone?

  5. Paul Davies permalink
    March 18, 2009 9:46 am

    No, I haven’t (from memory) come across anything specifically on snails rasping bone. Sounds like an idea for some experiments…

  6. matthewlaw permalink*
    March 18, 2009 7:52 pm

    I’m very glad you think so! I’ll see what I can do. Watch this space.

  7. April 7, 2010 6:57 pm

    This caught my eye in a big way. Thank you for writing up your discovery. I write children’s fiction books about African Land Snails and am now writing the fourth book, Snail Movie. I am researching alien snails for the fifth book -Snalien – so I would be interested in anything further you might have to say about alien snails. Thank you! Sarah

Trackbacks

  1. A resident alien snail from Sawston, Cambridgeshire « Adventures in archaeology, human palaeoecology and the internet…

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