Snail senses

[danikat]

Does anyone know how good their eyesight is?

I've always wondered because sometimes my snails will look around as if they're looking at things more than a foot away, but at other times (especially when they're eating) their eyes will be almost touching whatever they're looking at.

I don't really know of a way to work it out without testing them, maybe putting food at different distances and see if they notice, but I'm hoping someone might have already worked it out.

Renamed - CroSSLeSS

[crossless]

I think eyesight is not most important sense they have. Snails move mostly at night so it's always going to dark. So you never can know what they are looking at but it would be fun to know. Feel and smell I think are more important senses than sight.

[coyote]

I don't think anyone really knows exactly how well a snail can see. I do know that their eyes have lenses, which means they can focus their vision to some extent, so they can probably see better than we think they can. But I doubt they can see very well in spite of that, compared to higher animals.

[crossless]

I have image in my head that some animals can see and separate some colors, shapes and moving things. I don't know how it's different with some animals. So maybe it depend where they live, like if snails on ground it has to see at least shapes, like food on plate and go direction of smell&sight. I have noticed they can't estimate how far some object it from them. Example one snail is "sitting" on side of high edge food plate wants to climb on wall. It try, try and try reach to wall and foot gets longer and longer, then it notices you can't get there it starts to move closer till it feels wall. Same when they try to reach from branch to walls.

[danikat]

I've noticed that, or on the other side of things they'll be on a plate just above the table and if they reach slightly over the edge and don't touch anything they won't go down, even though it'd just be a tiny step.

So I suppose their eye sight can't be that good over long distances at least. Mine do seem to like to see what they're eating though, they'll usually have both eyes curled down right in front of thier face. ;D

[crossless]

Weird and funny looking thing is when they feel if it's ok to go forward and eyes bounces back from walls *Boingboing*

[Bumblebee]

Well snails do seem to have very poorly eyestight, since during a few ocassions when I have tried to give mine some foods they never tasted before, and I'd hold up a little piece in front of them to see their reaction to the food, they havnt noticed the food untill either their feelers, or one of their eyestalks bumps against the food, wich then have made them look in that direction.

I've also been told that snails can only see light and dark...

Lol im so curious about how the snails have been able to exist for so many years Their shells isnt that strong like a turtles, they seem to have poor eyesight... xD

[crossless]

My snails are good at hiding, sometimes it's really hard to notice them.

[coyote]

Snails find food by smelling more than seeing. They don't have to have a clear line of sight to find something to eat or a calcium source, because they can detect the molecules with their lower tentacles (I also read recently that snails have scent detectors in their eyestalks as well, so they baically have 4 noses).

Being nocturnal, they need either super-duper eyesight or else much stronger other senses to compensate for not being able to see well in the dark.

As I said, no one really knows how well snails can see. But the fact that they can focus their vision with the lenses in their eyes probably means they can see more than just light and dark.

[Robert Nordsieck]

Hi there,

snails are not exclusively nocturnal, but when I wrote about the Roman snail, I read that they have not a sufficient number of light sense cells to differentiate between colours, so they can only see black and white. As besides their eyes have got a rigid lens, that cannot change its form and so cannot focus, I think the picture their eye sees, is also very much blurred.

Senses and Sense Organs of the Roman snail (Helix pomatia, of course also applicable to other terrestrial pulmonates.

Regards
Robert

[coyote]

Thanks, Robert, for posting that article.

Although I'm puzzled by something -- why would a snail eye have a lens if it cannot be focused?

[aerliss]

The lens will focus light onto the retina on the back wall of the eye. This would mean (I assume) that they can see shapes (if blurry and in monochrome) as opposed to just detecting light and dark (like maggots and worms).

[Robert Nordsieck]

Oh, I am sorry, that was a language problem. Of course the lens does focus, but it cannot adjust to changing distances to the object. That means, snails can see, what is in their focus, but not beyond.

There are of course very different types of eyes in the Gastropoda class, but I think we are talking about terrestrial snails here.

Kind regards
Robert

[coyote]

Ah, now I understand! Thanks for clarifying that, Robert.

[crossless]

www.applesnail.net/content/anatomy/senses.php Heres more about eyesight. Really interesting

[coyote]

That's a very interesting link; I'm bookmarking it. Thanks for posting it.

[crossless]

It's worth of reading all those articles on that web site there is all about snails digestions process and many other interesting things too.

[lee2211]

I read somewhere that snails can't see very well and they rely mostly on their sense of smell.
They're also practically deaf, and can apparently sense humidity ect. But I don't know how reliable this information is as I can't remember where I read it

[coyote]

What you read appears to be true, lee.

[lee2211]

Well that's good
I thought it sounded pretty cool but I wasn't sure wether to believe it or not.
Snails are so clever, yet they are perceived to be such simple minded creatures.
Oh well, more for us then