Mammals and octopuses have evolved very differently evolutionarily.
A new study may show that their sleep cycles are similar to each other.
Brazilian researchers made video recordings of four octopuses of the species Octopus insularis.
In the recordings, two different sleep states could be identified - a calm phase of sleep and an active one.
Like human sleep
During the calm sleep phase, which is similar to humans' deep sleep, the octopuses lay still in their cages with colorless skin and closed eyes.
During the active phase, something happened to the octopuses.
Their skin varied in both color and texture and their eyes also seemed to move, much like how human eyes move during REM sleep or dream sleep as it is also called.
- An octopus brain does not look at all like a brain in a vertebrate animal.
When you compare the components of the different brains, you can see that they are very similar, even though they are structured in completely different ways, explains Dan E. Nilsson, who is a professor of functional zoology at Lund University and has read the study.
Dream sleep sign of intelligence
It is possible that octopuses experience something like dreams during the active sleep phase, according to the study.
- Dream sleep is special and has enough to do with more advanced intelligence.
For further research, it would be interesting to look at exactly what is happening in the octopus brain, says Dan E. Nilsson.
Play the clip to see how the octopuses change color.