Animals dream like humans too

Can you dream too? : Octopus sleep phases similar to humans

Similar to humans and other mammals, octopuses alternate between two different sleep phases: A quiet sleep phase is interrupted by an active one in which the animals suddenly change their skin color, move their eyes or contract their suckers. This is what Brazilian scientists report in the specialist magazine “iScience”.

The active sleep phase is similar to what is known as REM sleep in humans, during which most dreams occur. The scientists speculate that octopuses may also have dream-like experiences in their sleep, which should, however, resemble "rather short video clips or gifs" than detailed dream stories, as main author Sylvia Medeiros from the University do Rio Grande do Norte explains in a communication.

The researchers had filmed four octopuses of the species Octopus insularis sleeping in an aquarium. It was already known that the animals sleep at all and occasionally change their skin color. To sleep, the octopuses seek a preferred resting place, drop their heads and wrap their eight arms around their bodies.

The evaluation of the recordings showed that the animals lie largely motionless during the quiet phases of sleep, the skin is pale and their pupils are narrowed to a slit. Such phases lasted an average of more than six minutes.

This was followed by a short active phase lasting only about 40 seconds. In a video by the researchers you can see how the skin color of the animals changes at lightning speed, for example turning from a light orange to a deep red.

Octopuses sleep soundly

The eyes and various muscles of the body move and the suction cups contract. In this active phase, too, the animals were difficult to reach with visual or vibration stimuli - they actually slept soundly.

In mammals such as humans, birds or some reptiles, REM and non-REM sleep phases alternate during sleep. REM stands for Rapid Eye Movement, because during this phase the eyes move violently behind the closed lids. During non-REM sleep, blood pressure and body temperature drop, the sleeper hardly dreams.

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"The change in sleep states observed in Octopus insularis seems to be quite similar to ours, although the lineages separated about 500 million years ago and thus there is an enormous evolutionary distance between cephalopods and vertebrates," explains Medeiros.

Certain nervous systems may make sleep necessary

If this sleep pattern actually developed independently of one another in vertebrates and invertebrates, the question arises as to which evolutionary forces are responsible for it. The property may develop when a centralized nervous system has reached a certain level of complexity.

Whether the octopuses actually dream during the active sleep phase cannot be answered. "If octopuses are actually dreaming, they are unlikely to experience complex symbolic acts like us," says Medeiros.

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"Active sleep" in the octopus has a very short duration - usually from a few seconds to a minute. If one dreams in this state, then the dreams are more likely to resemble short video clips or gifs. It is tempting to speculate that dreams also help octopuses to learn and adapt to the environment, says study director Sidarta Ribeiro.

Researchers want to measure brain activity in octopuses

Do octopuses have nightmares? Are your dreams reflected on the dynamically changing skin patterns? Could we learn to read their dreams by measuring these changes? In order to get closer to answering these and numerous other questions, the scientists want to conduct further studies, among other things, to measure the brain activity of the animals during sleep - a challenge for the molluscs living underwater.

Octopuses are a genus within the family of real octopuses that are considered to be very intelligent animals. You can loosen screw caps on glasses or assess whether your body will fit through an opening or not. In addition, they are able to adapt their body color and pattern to the respective environment in a flash.(dpa)

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