Octopuses can ‘see’ with their arms, even when they are in total darkness at the bottom of the sea. This is the conclusion reached by a group of researchers from the Ruppin Academic Center (Israel). Also, when octopuses detect light, they bring their eight arms closer to their body. Since octopuses don’t have a good sense of space, this instinctive behavior could help them protect their arms from the pincers of nearby predators that they might not otherwise be able to perceive.
Also, scientists have known for quite some time that octopus arms react with light. Their skin is covered with pigment cells called chromatophores that instinctively change color by reflex when exposed to light. In addition, thanks to these cells, octopuses can also camouflage themselves and change color.
Investigation Development
During an investigation, the scientists were shining a flashlight on the octopus’s arms to elicit a response from the chromatophores. However, they discovered by accident that when they shone a strong light on the animal, it would always drift away and be uncooperative. For this reason, they decided to change the research to better understand how they could ‘see’ through the arms.
The new experiment consisted of placing the octopus in a tank covered with an opaque canvas. The animal, which was completely in the dark, was trained to reach an arm through a small hole in the top of the tank, and thus find pieces of fish.
As the octopus blindly searched for its food, the researchers illuminated the octopus’s arm with bright light at random times. About 84% of the time when the octopus was illuminated, it would quickly withdraw its arm, suggesting that the animal is capable of reacting to light with its arms even when it cannot see it with its own eyes.
The scientists also took into account temperature changes, since people can feel the heat of an intense light. However, this was not the case for octopuses, as the researchers used pure light and checked for changes in temperature.
Now scientists are focused on understanding the evolution of this behavior.
