You probably don’t think a lot about snail eyes, but they’re actually super fascinating. Well, they are if you’re into that kind of thing. (Which I am, obviously.)
How about I kick things off with a couple of fun facts about snail eyes?
1: Some snails don’t have eyes at all, while others are in the process of losing theirs.
2: Snail eyes are different, in pretty much every way, from human eyes.
3: Snails can do the equivalent of a human blink.
Don’t believe me? Let’s take a deep dive and find out more…
Do Snails Have Eyes?
Yes, snails do have eyes. They are located at the end of the top tentacle pair ad are known as vesicular eyes. This means they process and focus differently from human eyes, using their eye stalks for focusing and change the direction of the vision.
Humans do not have eye stalks (obviously). Instead, we use cilia muscles, which are hair-like structures, for focusing the images our eyes see.
How Many Eyes Do Snails Have?
Most snails have two eyes, just like me and you.
There are snails, however, that don’t have any eyes at all. There are also snails that have eyes, but don’t use them to see, and there are even a few species that are losing their eyes and/or eyesight. These are underground and deep-sea snails, particularly those from the Solariellidae family.
That’s just the way the evolutionary cookie crumbles.
It might look like some snails have four eyes – two taller ones at the top of the head plus two shorter ones below. The ones at the bottom are not eyes, however. Instead, they act as a nose-like organ. Snails use their sense of smell to find food, locate predators, and more.
Where Are Snail Eyes?
The location of the eyes on a snail will depend on the species. Land snails usually have two tentacles or eye stalks on the very top of their heads. These are also known as ommatophores.
Some sea snails also have a similar design, but many have eyes that are located at the bottom of the body, also known as the foot.
Snails that live underground don’t really need eyes, and they’d probably get in the way if they did. There are a few underground species that don’t have eyes at all.
What Do Snail Eyes Look Like?
On a Roman snail or garden snail, you can clearly see the two longer tentacles or eye stalks protruding from the head. They are usually a shade or two lighter than the main body, with a dark brown or black dot right at the end. The black dot at the end is the equivalent of a human iris.
The end of the eye stalk, where the darker-colored dot is, is usually bulbous and eye-shaped.
Giant African land snails have the same eye stalks with bulbous tips, as do saltwater turbo snails and a wide variety of others.
Some species, such as those from the top shells and ormer families, have evolved to have pinhole camera-style eyes.
Why Do Snails Have Long Eyes?
Snails have long eyes because they work differently to human eyes. Human eyes have a serious of muscles and other bits and pieces behind the eye itself, which help to focus, process the image, and more.
Snails do not have those muscles and other bits and pieces. Instead, the long tentacles help them to focus and process information. It’s just a slightly different setup.
Do Snails Have Good Eyesight?
No, snails don’t have good eyesight. Human eyesight is believed to be much better than snail eyesight.
Snails would see blurry images, without a lot of light, and possibly without color. The light and dark, particularly in the water, would alert the snails to predators, potential food sources, and a lot more.
The tentacles below the eye stalks are essentially the snail’s nose, which it uses alongside sight to help build a picture of the world around them.
Why Do Snails Eyes Retract?
Snails’ eyes retract for the same reason that we can blink: to protect them! Snails don’t have an eyelid, so they need to have some way of protecting their eyes. Retracting them into the body, and then the body into the shell, helps to keep them protected and safe.
Snails use their eyes to help find food, although it isn’t the only approach they take. If the eyes were to become damaged because they couldn’t be retracted, the snail would struggle to feed.
What Happens When You Touch a Snail’s Eye?
If the snail has retractable eyes, they will, of course, retract into the body. If someone were to poke YOU in the eye, you would blink and move away. When a snail retracts the eyes into the body, they’re basically doing the same thing.
Can Snails Eyes Grow Back?
Actually, yes, some snail species can regrow their eye stalks. This is similar to some lizards, which can regrow tails if they are broken, damaged, or snapped off.
Mystery snails are one example of a snail that can regrow eye stalks when they are damaged.