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Pond snails

Posted: Wednesday 4 July 2012
by Richard Jones

[...] pond snails are much more delicate than their terrestrial counterparts — slimmer and more elegant.


Water snail in a vase

About once a year I try and slide in a blog about snails, and, for 2012, this is it. But I’m not going to go on about how pretty I think are the shells of the garden snail (Helix aspersa), or how they are only pests if they reach pest proportions. No, I’m beyond trying to convince gardeners they are anything but a nuisance. So instead, I’m going to pontificate about pond snails.
 
We have not deliberately inoculated our small garden pond with snails, I know you can buy them from aquatic centres; they have come in under their own steam. I don’t imagine for a moment that they have actually crawled from a neighbouring water body. They must have come in, accidentally, as eggs or very small snail-lings, with some of the water plants we threw in unceremoniously when we built it 10 years ago.
 
I have not had a close look at Lymnaea stagnalis since going pond-dipping as a boy. I hear now that remembered squelch of air being expelled from their shells as I fish them out of the water — a defence as they lose buoyancy and try to sink into the dark water below. But my fingers are too quick for them.
 
The first thing I notice is that they only have two tentacles, unlike garden snails, which have four. Instead, the whole front of the head is extended and flattened into a broad flange, with which they fondle their way around. The two broad pointed flaps sticking out from the head look rather like Yoda’s ears, and there is definitely something comical about them. I’m struggling to see any eyes, but my researches disclose that the two tiny black specks at the bases of these lobes are light-sensitive patches.
 
All in all, pond snails are much more delicate than their terrestrial counterparts — slimmer and more elegant in succulent body and more refined in the sharp spire of their shells. Surely, nobody is going to claim that water snails are pests, are they? Oh, but don’t tell anyone I used one of our best vases to display them on the kitchen table.





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