Snails' sense of balance

[snailbutler]

Whenever I put my snails back in the tank after giving them their weekly wash, I try to put them on one of the objects in the tank so that they don't get dirty again straight away (why I do this, I've no idea). Anyway, when I place them down they will usually face upwards as if they're looking for something above them, and they seem completely oblivious to the prospect of falling over. Considering this behaviour and the fact that they don't have ears, I wondered whether snails have a sense of balance.

[coyote]

That is an interesting question. Since snail slime is like a glue that keeps them stuck to whatever they're on, I suppose a snail would have little awareness of the possibility of falling. Even when they are estivating or asleep on the side of the tank they stay stuck. It's not even a conscious decision on their part to stick to something, it just happens automatically. And considering the amount of time a snail spends upside-down on the lid of a tank, if it had a sense of balance like humans do, it would get dizzy pretty quickly, so I doubt the biological mechanism is similar, if it exists at all in a snail.

I do know they have a sense of up and down, but other than that I have no idea what else is going on for them to be oriented.

[Robert Nordsieck]

Hi there,

it does exist!
Snails have two statocysts on either side of their peri-esophageal neural ring (what a word). Those are liquid-filled capsules, in which grains float. When the snail moves the grains are carried towards to walls of the capsule where sense hair detect the contact and produce a neural stimulus.

I think, snails would not be able to perform some of the stunts they do in nature, like this one:


Source: weichtiere.at

Kind regards
Robert

[coyote]

Thanks for the explanation, Robert.

[snailbutler]

That's very interesting. Thinking about it, I suppose the fact that they look upwards when I place them down indicates that they know which way up is. I certainly wouldn't want to rest whilst clinging to my ceiling upside-down, but I guess snails don't associate being upside-down with instability in the same way humans do.
The aspect of their behaviour that seems odd to me is that they seem more interested in surveying their immediate surroundings than in extending their foot and becoming stable. If most animals were put on their side, I imagine the first instinct would be to right themselves before looking around. I've strayed a bit from the subject there though. Thanks for your replies.

[coyote]

The snail's slime keeps it stuck to whatever surface it's on, so it doesn't worry about falling.