Although the octopus is famous for its many weapons, it seems that most of the time the octopus does not know where the eight appendages are.
Nir Nesher, senior lecturer in marine science at the Ruppin Academic Center in Israel, said: “In an octopus, you have no bones and no joints, and every point on your arm can develop in all directions you can consider.” So even one arm , Also like endless degrees of freedom. “
So how can octopus get rid of all those limbs that are covered with suckers? According to a study published this month by Dr. Nesher and his colleagues in the Journal of Experimental Biology, the octopus̵
One of the authors of the study, Itamar Katz, first noticed the ability to detect light when studying a different phenomenon: how light changes the skin of an octopus. While with another author, Dr. Nesher and Tal Shomrat, Mr. Katz saw that the light on his arm made the Octopus withdraw, even though the animal was sleeping.
Further experiments have shown that when the octopus’s eyes are invisible, the arms will avoid light. Even if the octopus reaches out an arm from a small opening in the opaque covered aquarium, the arm will retract quickly when it is exposed to it 84% of the time.
Dr. Nesher said this was surprising, as if the octopus “can see the light passing through the arm, and can feel the light passing through the arm.” “They don’t need eyes.”
The light response behavior of the arm also adapts to changing conditions. When the octopus is left in the dark for a week or a month, the reflection of exiting light becomes faster, but it also needs brighter light to activate it.
This ability to perceive and adapt to light is likely to consume a lot of energy, indicating that behavior is essential for the survival of octopuses.
Dr. Shomrat said: “We speculate that this reflex is to protect the arm and keep it folded so that when crabs or fish think they are worms, no crabs or fish will bite it.”
However, how the octopus’s arm detects light is still a mystery, let alone the light. Katz said there is evidence that light-sensitive receptors exist in the skin, but there is no direct evidence that they are responsible for the behavior.
Surgical experiments performed under anesthesia and carefully minimized pain did provide some clues. When the octopus is separated from the body or anesthetized, the arm stops retracting from the light. Although vision is not required for behavioral responses, it still requires a complete brain. Still strange, the reflex also seems to depend on something in the arm muscles-only when the skin is cut, the reflex is still there, not when the underlying muscles are also cut.
Understanding how the octopus arm completely avoids light is the next step in understanding this unexpected behavior.
Dr. Nasr said: “But octopuses are always like this.” “You see very strange or very interesting phenomena, and then you say,’Oh, no one has seen it before.'”