The only animal that looks with ... legs

Since there were no eyes, sea urchins used light-sensitive cells in tassel tubes like tentacles at its feet to feel and see everything around them.

According to the Daily Mail, sea urchins are by far the only animal that can see without eyes. Researchers have found that the legs with the tentacles attached to them help the sea urchin look just enough to meet its basic needs.

Sea urchins - (Photo: AFP).

In fact, everyone knows that when threatened, sea ​​urchins will pry their feathers to protect themselves. But how do these animals know they are threatened when there are no eyes? That is the question that has been a headache for the world's marine biologists.

It was not until 2011 that scientists discovered sea urchins could see with their feet. But now, with the latest research results, researchers at Lund University in Sweden also know how good sea urchins can look.

Researcher John Kirwan explains: "Sea urchins are currently the only animal that has been shown to be able to see without eyes . They look by using light-sensitive cells in tubular legs, like contact. You can say that the whole body of a sea urchin merges into a single eye. "

Researchers learned about the ability of long-haired sea urchins to look, giving them the same "eye test" as humans. Accordingly, they placed these porcupines in a illuminated cylindrical tube and many dark images on the wall.

The visibility of sea urchins is very limited.(Photo: GETTY IMAGES).

"Normally, sea urchins tend to move towards dark areas to find cover. When I realize they react to images of this size and not other dimensions, I can measure how their "sophistication" is " - Kirwan said.

He projected many different images on the wall and then the shadows of those images covered the sea urchins similar to a predatory object approaching the hedgehog.

Next, Kirwan can calculate how big these shadows begin to envelop the new sea urchin with self-defense moves by ruffling towards the shadow above.

However, the researcher also found that the ability of sea urchins to see is very limited. In the 360-degree space of the environment surrounding sea urchins, an object must cover at a projection angle of 30-70 degrees before the sea urchin is discovered.

Meanwhile human vision is much better. An object that only needs to fall into a view angle of about 1/60 degrees, humans can detect it immediately.

"However, this vision is sufficient for the animal's needs and behavior. It's obviously not poor vision for an animal without eyes," concluded researcher John Kirwan.