Scientists in Israel, in a serendipitous discovery while studying the causes of skin colour changes in the cephalopod due to light, have made a shocking discovery. They found that octopus arms can sense a beam of light and evade it even when its eyes cannot see the light. 

In a series of tests and investigation, the scientists discovered that shining a light on an octopus's arm caused the animal to repudiate it, even when it was slumbering, and while the source of the light was present on the other side of a small opening into which its arms could fit but the light was unseen to its eyes.

(Photo : Pia)

Research Findings

These findings are published in the Journal of Experimental Biology this month. The research was authored by Itamar Katz, Tal Shomrat, together with Nir Nesher of the Ruppin Academic Center in Israel. 

Past studies have revealed that octopuses display a phenomenon known as light-activated chromatophore expansion (LACE), which is independent of the eye. This means that when light is beamed on an octopus arms, they show the potential of expanding colour-producing cells or chromatophores. 

The scientists in Israel had built up experiments to look into this phenomenon when they realized that upon shining light on an arm of an octopus, it repudiated its arm like a reflex, folding and moving away from the beam of discharged light, even when it was sleeping. 

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The Color-producing Cells 

The researchers set up more experiments to determine how this procedure works.

This includes experimental build-ups where octopuses had to extend their arm through a small opening in an intransparent, enclosed container for food. When the light was beamed on the arm, despite the fact that the animal's eyes could not see it, the animal still retracted its arms about 84 percent of the time. 

As circumstances changed, the behaviour and responses also adjusted. When octopuses were kept in the dark for a week, their reflexes became faster and stronger, but the brightness of light needed to initiate this response increased. 

Safe surgical experiments offered more insights: octopus arms stopped responding when they were either detached from the body or the animal was under anaesthesia, signalling that the brain was coordinating this response. Furthermore, when a slight cut was made on the skin, the reflex remained, but cuts made to the muscle underneath led to its loss.

(Photo : Ann Antonova)

What Findings Reveals About Octopuses 

Octopuses are believed to have poor ability for the understanding of position and movement of the body. Researchers believe these cephalopods do not always know where their tentacles or free-moving arms are. This brought up questions on how they can effectively and efficiently hide or camouflage when a situation emanates.

The researchers now conceive this ability to reflexively retract from light guides the octopus when hiding from predators, or hunting for animals, or keeping safe while sleeping.

Nevertheless, the science following the octopus arm response to light is still a mystery. Researchers hope future investigations can provide more views into this highly intelligent animal's unique evolutionary adaptations. 

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