The octopus is an extraordinary creature, and not just because of its eight limbs, three hearts, blue blood, splashes of ink, camouflage ability and the tragic fact that it dies after mating.
A study by Brazilian researchers published on Thursday shows that this animal, which is already considered perhaps the most intelligent invertebrate, experiences two important alternating states of sleep, very similar to humans, and could even dream.
The findings, according to the researchers, provide new evidence that pop possesses a complex and sophisticated neurobiology that is based on an equally sophisticated behavioral repertoire, while offering a broader view of the evolution of sleep, a crucial biological function.
Previously, octopuses were known to experience sleep and change color as they slept. In the new study, researchers observed a species called Octopus insularis in a laboratory. They found that these color changes were associated with two distinct sleep states: “calm sleep” and “active sleep.”
During “quiet sleep,” the octopus remains still, with pale skin and pupils of the eyes contracted to a crack. During “active sleep,” it dynamically changes skin color and texture and moves both eyes as it contracts the suction cups and body, with muscle contractions.
A repeated cycle was observed during sleep. The “quiet sleep” usually lasts about seven minutes. Subsequent “active sleep” used to last less than a minute.
According to the researchers, this cycle seems analogous to the sleep states experienced by humans, as well as other mammals, birds, and reptiles, alternating “rapid eye movement” or REM, and “non-rapid eye movement” or non-REM. .
Living sleep occurs during REM sleep, as a person’s eyes move rapidly, breathing becomes irregular, heart rate increases, and muscles become paralyzed to not represent dreams. Non-REM sleep presents a deeper sleep and fewer dreams.
The study’s lead author, Sylvia Medeiros, said the findings suggest that octopuses may be dreaming or experiencing something similar.
“If octopuses really dream, they are unlikely to experience complex symbolic plots like us,” said Medeiros, a doctoral student in neuroscience at the Brain Institute at the Federal University of Rio Grande do Norte.
“Active sleep” in pop lasts a very short time, usually from a few seconds to a minute. If during this state there is a dream, it should be more like small video clips or even GIFs “, added Medeiros.
Scientists are looking to better understand the origins and evolution of sleep.
Because the last common ancestor of vertebrates, including humans, and cephalopods, including octopuses, lived more than half a million years ago, it seems unlikely that their similar sleep patterns were established before their divergence. evolutionary, the researchers said.
This would mean, they added, that this similar sleep pattern arose independently in the two groups, a phenomenon called “convergent evolution.”
“Research on sleep and sleep in octopus provides us with a point of view for psychological and neurobiological comparison with vertebrates, as octopus possesses several sophisticated cognitive characteristics that are only seen in some vertebrate species but with a brain architecture very different, ”he said. co-author of the study Sidarta Ribeiro, founder of the Brain Institute.
Ribeiro noted that previous studies showed 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 animal cognition research and for understanding the general principles that shaped brain design in these groups of highly intelligent animals, ”Medeiros said.