Do you remember the birch looper in the junior high school biology textbook? Its larvae use their skin to "see" the world

Boas once said that eyes are the windows to the soul, and a person's intelligence and will can be seen through them.

For human beings, eyes are extremely important. They can see into the inner world as well as the external world.

But in this vast world, eyes do not seem to be very important to some animals, because they can see the world without using eyes.

Just like this caterpillar - the birch looper.

Perhaps you are unfamiliar with this little guy, but I believe many people have an impression of its adult form.

After all, it has appeared in everyone's junior high school biology textbook. I remember it appeared in the topic of evolution. As an example, it talks about the changes in the local environment in Manchester, England due to the emergence of industrialization. In order to avoid natural enemies, black individuals evolved from the originally white birch moth group.

The larvae of the birch looper can actually change color. The professional term for this is mimicry, which refers to the phenomenon whereby one organism imitates another organism or other objects in the environment to gain benefits.

It can change its own color according to the color of the plants it is in, brown, green, white, etc. To this extent, it can be called an expert in biological color change.

Scientists have also conducted special experiments on birch looper larvae. They placed the birch looper larvae on poles of different colors for observation. The results showed that the birch looper can indeed change color according to the different colors of the poles it is on. Even on poles of different shades of green, subtle color changes will occur. Such color changes are really very precise.

In order to better hide itself, this little guy sometimes even imitates tree branches. You know what, the imitation is quite realistic and you can't tell it unless you look carefully.

Of course, there is a prerequisite for the birch looper larvae to perform these mimicry. They must first sense the outside world. Especially this kind of color change, they must first sense the color of the external environment.

In this case, eyes are definitely needed.

But scientists have discovered that the eyes of birch looper larvae are not only small, but also have a smaller role, because the structure of the eyes of birch looper larvae is too simple.

It has only one simple photoreceptor - a single eye (an eye system consisting of visual cells, a hexagonal cornea and a conical lens). This single eye cannot see the color and shape of external objects, but can only perceive the intensity of light.

Since these eyes are so "irresponsible", what do the birch moth larvae use to accurately perceive the colors of the outside world and complete the mimicry changes?

To this end, scientists conducted a test.

They first tested whether there was opsin (a protein with light-sensing ability) in the eyes of the birch looper, and as expected, the protein was present.

Then they tested whether the skin of the birch moth larvae, which has the most contact with the outside world, contained visual proteins. The result was really unexpected, because the skin had a similar level of visual protein expression as the eyes, which means that its skin can "see" things like the eyes.

In order to further confirm that the birch looper has photosensitive organs other than eyes, scientists conducted an experiment.

Scientists painted black acrylic paint on the eyes of birch moth larvae to prevent them from receiving information through their eyes and eliminate their ability to sense light, and then placed them on poles of different colors for observation.

Painting the eyes of birch looper larvae may sound simple, but it's a big project.

Because the eyes of these larvae are too small, scientists can only stare at them under a microscope to color them. The key is that the growing larvae will shed their skin many times, and the paint will fall off during the molting process, so they have to be re-colored every time they molt. However, this also ensures that the birch looper will not become blind after the experiment.

After painting the eyes, scientists placed these "invisible" birch looper larvae and normal birch looper larvae on poles of different colors for observation.

The results showed that even if the birch looper larvae are "invisible", they can still successfully change color and complete mimicry like normal birch looper larvae.

Moreover, it can not only change into the solid color of the corresponding rod, but also change into stripes according to the striped rod. From this, it can be determined that the birch looper larvae can use skin without eyes to complete the color perception of the outside world and complete mimicry.

I have to say this skin is quite strong, the skills are perfect!