Most worms live in the darkness of the soil. Therefore, it would be natural to think that they do not have eyes. But how then do they sense the environment?
Worms are not a type of animal that people like to think about. But they play an important role in the Earth’s ecosystem. Their biology also raises some interesting questions. For example, how do they navigate around, or how do they know where they are going? Here are the key facts about the worms’ visual system and the perception of the surrounding world.
How do worms see the surrounding world?
Do worms have eyes? No, worms do not have eyes. At least in the same sense in which we think about our own ability to see the world. However, worms have sensory receptors in their skin. They detect light and send this information to the worm’s body.
This way, worms may sense changes in light intensity and tell if they’re underground or above ground. But they cannot distinguish shapes and colors in the way our eyes can.
The light-sensing cells are located within the epidermis, in the top part of the worm’s body. Each sensory site is connected to a number of nerves running through the body. The majority of these sites are near the mouth and in the frontal part of the body.
How do worms use their ability to sense light?
Light sensitive areas let the worm understand if it emerges to the surface. Most often, these creatures avoid light, so these receptors function as a type of alarm warning them of potential danger.
For worms, most of the food they eat is underground, so there is no point in traveling out of their comfort zone. On the contrary, on the surface, they can be easily noticed by predators and they do not like to go there unless it is absolutely necessary. In most worms, excessive exposure to light also interferes with their ability to move. This is why they need to understand whether they are exposed to light or not.
By the way, many worm species can sense different light colours. For example, they may avoid white or blue light, but may actually be quite indifferent to red. This is the case with earthworms – even their ability to sense red wavelengths is quite poor.
Besides their ability to “see” the light, worms also have touch sensors that let them find food and mating partners.
What other senses do worms have?
They can also feel the vibrations in the environment. This way they can detect the presence of nearby animals. There are also certain species of predatory worms that use sensitive appendages on their heads to help them locate and capture food.
Worms also have specialized cells that react to heat and chemicals. Thanks to them, they can react timely to potential environmental dangers and survive even without having normal eyes.
Are there any worms with normal eyes?
As a rule, if the worm lives underground, it does not need any eyes. However, there are some rare worm species that actually have specialized visual organs which can be called eyes. One example is this marine worm. Although, they are still quite different from our human eyes.