Can a Worm See?
Earthworms don’t have eyes, so they can’t see images or shapes like other animals can, but they can detect changes in light. Read on to learn more.
A worm can’t see forms or colors, and a worm definitely can’t appreciate the beauty of a sunset, but in one sense, a worm can “see” the sunset. Worms have light-sensitive cells scattered across their skin that can detect changes in light intensity, so when the sun goes down and it becomes dark outside, a worm can feel the difference.
Earthworm Anatomy
Earthworms are fairly basic creatures. They have elongated, segmented bodies, which they scrunch up and stretch out again to push themselves forward. At first glance, they look perfectly symmetrical. Because they don’t have eyes, it’s hard to tell which end is the head and which is the tail, but the head does have a mouth, and the tail does have an anus. Inside, worms have two blood vessels, one that pumps blood from the heart to the tail, and another that pushes the blood from the tail back up toward the head. Worms have five hearts, a digestive system and one nerve cord that runs the length of the body. A worm’s brain is tiny and essentially serves one function: to direct movement in response to light. If you removed a worm’s brain, not much would change.
Do Worms Like Light?
The obvious next question is this: If worms can only detect light, and if the brain serves mostly to move in response to light, what is a worm’s relationship with light? Do they like it, or do they want to stay away from it?
Most of the time, worms stay underground. It’s safer there for them because they probably won’t get squished and they can stay moist underground, which they need in order to survive. Worms “breathe,” you see, by taking oxygen in directly through the skin.
This process is facilitated by mucus on the worm’s skin. If worms are above ground for too long, they might dry out and die, so their light-sensitive cells tell them when it’s time to head back underground. However, when it’s time to mate, worms prefer to surface, and their light sensors help guide them in the right direction. So now you know what a worm can see, how it sees it, and why it needs to see at all.