Octopuses Change Colours While Slumbering, Have 2 Sleep Cycles Eerily Similar to Humans, Finds Study

The octopus is an extraordinary creature – and not only because of its eight limbs, three hearts, blue blood, ink squirting, camouflage capacity and the tragic fact that it dies after mating. They found that these color changes are associated with two distinct sleep states: “quiet sleep” and “active sleep.” During “quiet sleep,” the octopus remains still, with pale skin and eye pupils contracted to a slit. This cycle appears analogous, the researchers said, to the alternating “rapid eye movement,” or REM, and “non-rapid eye movement,” or non-REM, sleep states experienced by people, as well as other mammals, birds and reptiles. That would mean, they added, that this similar sleep pattern arose independently in the two groups, a phenomenon called “convergent evolution.” “The investigation of sleep and dreaming in the octopus gives us a vantage point for the psychological and neurobiological comparison with vertebrates, since the octopus possesses several sophisticated cognitive features that are only seen in some vertebrate species but with a very different brain architecture,” said study co-author Sidarta Ribeiro, founder of the Brain Institute. “The understanding of how organisms as different as humans and octopuses can share fundamental traits such as the sleep cycle opens new avenues for the investigation of animal cognition and for the understanding of the general principles that shaped brain design in these groups of highly intelligent animals,” Medeiros said.