Octupi Sleep Patterns

In a recent Brazilian study, scientists discovered that octopi enter two sleep cycles at night. When they sleep, Octopi alternate between "quiet sleep" and twitchy, active sleep" in which vibrant colors flash across the animals' skin. These findings may provide clues to a big scientific mystery: Why do animals sleep? Sleep is vital to every species. Sleep patterns have been cataloged and tracked across myriad species - reptiles, birds, fish. Scientists have yet to find a species that doesn't sleep.

During this experiment, four wild octopuses, Octopus insularis, were caught and brought back laboratory to be studied. As the scientists recorded Ocupi behavior, two distinct states emerged. In the first stage of sleep, called quiet sleep, the octopi were pale and motionless with the pupils of their eyes narrowed to slits. In the second phase, active sleep, scientists observed the octopus's eyes dart around, suckers contract, muscles twitch, skin textures change, and, most dramatically, bright colors race across octopuses’ bodies. This wild sleep is rhythmic, happening every half an hour or so, and brief. Active sleep is also rare; the octopuses spent less than 1 percent of their days in active sleep, the researchers found.

Active sleep in octopuses is somewhat like REM sleep in people. But because octopuses’ active sleep is so short, their sleep cycles more closely resemble the sleep of reptiles and birds.

For people, REM sleep is packed with dreams. Scientists are tempted to try to read octopuses’ dreams on their skin. But as fun, as it is to speculate, no one knows what the octopuses experience during these active sessions of vibrant, flickering color. Researchers have a lot more work to do before they can say that octopuses dream. And even if it turns out that they do, those dreams might not make much sense to a human.

Scientists believe that in people, sleep is a way for the brain to organize its memory store, internalizing important, helpful memories and discarding irrelevant ones. Scientists hypothesize that a similar memory sorting process happens when an octopus sleeps. Perhaps the octopus is smarter than we had previously thought.

Sources:

S. Medeiros et al. Cyclic alternation of quiet and active sleep states in the octopus. iScience. Published online March 25, 2021. doi: 10.1016/j.isci.2021.102223.