The octopus is an extraordinary creature – and not just because of its eight limbs, three hearts, blue blood, ink splatter, camouflage ability and the tragic fact that it dies after mating.
A study by researchers in Brazil, published on Thursday, shows that this animal, already considered probably the most intelligent invertebrate, has two major states of alternative sleep, extremely similar to those of humans – and could even dream.
The findings, the researchers said, provide new evidence that the octopus possesses a complex and sophisticated neurobiology that underlies an equally sophisticated behavioral repertoire, while providing a broader perspective on the evolution of sleep, a crucial biological function.
Previously, it was known that octopuses experience sleep and change their colors while sleeping. In the new study, researchers observed a species called Octopus insularis in the laboratory. They found that these color changes are associated with two distinct sleep states: “quiet sleep” and “active sleep.”
During “quiet sleep”, the octopus remains motionless, with pale skin and pupils of the eye contracted in a slit. During “active sleep”, it dynamically changes the color and texture of the skin and moves both eyes as it contracts its suckers and body, with muscle twitching.
A repetition cycle was observed during sleep. “Quiet sleep” usually lasted about seven minutes. Subsequent “active sleep” usually lasted less than a minute.
This cycle seems similar, say the researchers, to alternating “rapid eye movement” or REM, and “non-rapid eye movement” or non-REM, sleep patterns experienced by humans, as well as other mammals, birds and reptiles.
Living dreams occur during REM sleep, as a person’s eyes move quickly, breathing becomes irregular, heart rate increases and muscles become paralyzed to not express dreams. Non-REM sleep has a deeper sleep and fewer dreams.
The study’s lead author, Sylvia Medeiros, said the findings suggest that octopuses may dream or experience something similar.
“If viscarps really dream, they are unlikely to experience complex symbolic plots like we do,” said Medeiros, a doctoral student in neuroscience at the Brain Institute at the Federal University of Rio Grande do Norte.
“The ‘active sleep’ in the octopus has a very short duration, usually from a few seconds to a minute. If dreams happen in this state, they should be rather small videos or even GIFs “, added Medeiros.
Scientists are looking for a better understanding of the origins and evolution of sleep.
Because the last common ancestor of vertebrates, including humans, and cephalopods, including octopuses, lived more than half a billion years ago, it seems unlikely that their similar sleep patterns were established before their evolutionary divergence. , the researchers said.
This would mean, they added, that this similar sleep pattern appeared independently in the two groups, a phenomenon called “convergent evolution”.
“The investigation of sleep and dream in the octopus gives us a point of view for psychological and neurobiological comparison with vertebrates, because the octopus has several sophisticated cognitive features, which are seen only in some species of vertebrates, but with a very different brain architecture.” said co-author of the study, Sidarta Ribeiro, founder of the Brain Institute.
Ribeiro noted that previous studies have shown that octopuses, with the most centralized nervous system of any invertebrate, possess exceptional learning skills, including spatial and social learning, as well as problem-solving abilities.
“Understanding how organisms as different as humans and octopuses can share fundamental traits, such as the sleep cycle, opens new avenues for investigating animal knowledge and understanding the general principles that shaped brain design in these highly intelligent groups of animals.” , ”Said Medeiros.