Eyes close, you get drowsy and suddenly you’re in dreamland. For a long time it was thought that only humans could do this. But now new research shows that even spiders probably dream when they sleep. This means that researchers now suspect that dreaming is a characteristic that all animals have in common. – Shows signs of REM sleep This week, researchers from Germany made a surprising discovery in jumping spiders. A team at the University of Konstanz in Germany observed the spiders when they were sleeping. – What we have seen is that jumping spiders show signs of something similar to REM sleep, says behavioral and evolutionary ecologist Daniela C. Roessler to news agency Ap. The German researchers observed the spiders in night light while they slept. This way they could observe movement in the pupils. Photo: Daniela C. Roessler / AP REM sleep is often called dream sleep. But does that mean that spiders dream when they sleep? – I personally think that they have visual dreams. But it will be difficult to prove scientifically, says the researcher. Important for preparing feelings Sleep researcher Rune Enger says that dreams are a way to clear impressions and stimulate the nervous system during REM sleep. Then the body is completely relaxed and one lies motionless, but the pupils move a lot. – In humans, REM sleep seems to be important for processing feelings and can therefore be important for fine-tuning social interactions, says Enger. But the spider is a more primitive creature than man. Spiders have about 100,000 nerve cells. Humans have about 100 billion brain cells. Photo: Iselin Fjeld / news In addition, spiders are not very social. – Why is REM sleep important for spiders? – One can imagine that there are certain types of memories that have to be played out in the spiders in order for them to think, but that they have to turn off their bodies so they don’t jump into a dangerous situation, says the researcher. – It could be that this is something similar to REM sleep and carries out the same functions. Sleep researcher Rune Enger says that you find something you think represents sleep in all the species they have checked. Even in animals that do not have a central nervous system. In other words, sleep can be important for animals such as spiders to remember and learn from things they have experienced. – Thinking of something will be of great value even for a simple creature, says Enger. During sleep, the researchers believe that the nerve cells that were active when you were awake are played again. In that way, memories are stored. Photo: Glenn Halvor Morka Octopuses change color when they dream And there are several animals that fell into such a dreamlike sleep. Also at the bottom of the sea. – We know that octopuses have REM sleep, says researcher Gro van der Meeren at the Institute of Marine Research. They never slept for more than an hour and a half, but during that time they always slept well. It is not certain whether all octopuses sleep and dream. The octopuses that swim constantly cannot be kept in an aquarium for research. Therefore, they do not know how they slept. Photo: Nils Aukran / And how do you know that squid have REM sleep? They change colour. – The pupils move and the suction cups pull out and together. The muscles do the same and the color changes in waves over the body, says the researcher. Octopuses also use their colors to communicate during the day when they are hunting, hiding or looking for a mate. Photo: Erling Svensen – There is hardly any doubt that octopuses also use sleep to filter and clear nerve impulses and impressions, says van der Meeren. Do you think all animals dream When one has discovered REM sleep in both mammals such as humans, in molluscs such as squid and arthropods such as spiders, the researcher believes that one can no longer think of dreams as unique to humans. Researcher Gro van der Meeren at the Marine Research Institute Photo: Tom Kjøde – When you see so many different animals in REM sleep, you start to wonder if dream sleep is something that most animal groups have. – If it comes from a common place in evolution, it has started early, says the researcher. Torbjørn Ekrem, professor of evolutionary biology at NTNU, believes it is more likely that dreams have evolved several times in the development of life. He thinks it has developed in animals when brain capacity has increased. – Mammals, molluscs and arthropods are completely different branches on the tree of life. Perhaps those with advanced brains have a greater opportunity to have such dream activity, he says. Researchers have studied toothaches to find out if they have REM sleep. But since they slept with one half of their brain at a time, the researchers do not think they are dreaming. Photo: Inge Wegge / One Whale Professor of zoophysiology, Lars Folkow, nevertheless points out that there is probably one mammal that does not dream: the whale. – If there are any species that do not dream, they are likely to be found in the ants, says Folkow. Kval only slept with one half of his brain at a time. – They must be present to come up to, for example, breathe. Then they need partial awareness. Therefore, they are not allowed to experience dreams. When the fur seal is on land, it shows signs of REM sleep, but in the sea, one half of the brain will have lower activity than the other, such as anguish. Photo: Tor Ivan Karlsen / Norwegian Polar Institute The researchers from Germany believe that the discovery of REM sleep in spiders can also provide more answers about human REM sleep. Sleep researcher Rune Enger agrees. – It might say something about why REM sleep arose in evolution. If you have it in both a spider and a human, you can imagine that sleep has several functions.
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Spiders dream, new research shows. Researchers believe that this applies to all animals. – news Nordland
