17 March 2012

Notes of a Cepaea watcher: an upside down snail

During our leisure hours at home, my wife and I spend most of our time in the library. The 3rd regular resident of the room is our cat who has a spot reserved for her at one end of the sofa. About a couple months ago, 2 Cepaea nemoralis joined us. The snails, originally from Frederick County, MD live in a large plastic container on top of a table by the sofa. The lid of the container is a large glass plate that provides an unrestricted view of the contents. So, when we are on the sofa we often find ourselves watching the snails, although most of the time they just sit upside down on the underside of the glass plate.

Even when the snails are doing nothing, there is quite to learn from them. In the picture above, notice how small a portion of its sole the snail was using to stay attached to the glass. The secret behind the snail's feat was a ring of slime around the rim of its aperture. That appears to be what is actually holding the snail in place.

You can also see the pneumostome, the breathing hole.


Petra said...

My very-much-domesticated Helix aspersas usually sleep like this without the slime-ring, only one of them seems to build the film when settling to rest lately. The rest just... hang there, holding on to the plastic ceiling with very little of the foot. Or they sleep like slugs, with most of the body outside but the head and eyestalks curled inside of the body. I've never seen a snail like that in the wild, so I assume it's some sort of conditioned behaviour. They never experience danger or lack of moisture, so they don't bother to withdraw into their shells. A human hand occasionally poking them with tweezers to remove poop strings before they dry on the wall isn't enough of a danger, I guess.

Anonymous said...

Isn't this perhaps a very light form of epiphragm that the snail has secreted? I mean, maybe it's not just a ring of mucus, but a very thin flat gluey Saran-Wrap-like cover, that is attached where you can see the ring?

Susan J. Hewitt