Have you ever observed your pets sleeping? Notice how their paws and whiskers twitch, and they make little sounds like yips and meows? Well, it turns out that cats and dogs experience REM sleep, which suggests that they dream. But have you ever witnessed an octopus sleeping? We came across a fascinating video clip featuring an octopus named Heidi, who undergoes color changes while she dreams.
While there is currently no definitive evidence of REM sleep in octopuses, they do have their own unique type of sleep twitch. Normally, octopuses undergo flickering movements when they sleep. When they are in a state of relaxation, their optic neurons become active, causing the chromatophores (pigment-containing cells) to be activated. Consequently, the octopus’s skin fluctuates between different colors and patterns while it snoozes, as if it is responding to its sensory experiences.
Sidarta Ribeiro and his colleagues, based at the Federal University of Rio Grande do Norte in Natal, Brazil, have discovered that octopuses experience two distinct stages of sleep: active and passive. The scientists recorded over 180 hours of video footage of four common octopuses (Octopus vulgaris) in a laboratory setting, spanning multiple days and nights.
According to Ribeiro, the animals spent more than half of the day sleeping. “They remain in the same position for extended periods, with closed pupils, extremely calm, and very pale. They also breathe quietly and regularly,” he explained.
During the passive sleep stage, which lasted for approximately 30 to 40 minutes, the octopuses occasionally experienced short bursts of active sleep lasting 1 to 2 minutes. Throughout this phase, the octopuses displayed changes in color and texture on their bodies, including the emergence of fine bumps known as papillae on their skin. The creatures’ eyes and arms also exhibited movement. “It’s quite remarkable to observe,” Ribeiro remarked.
To determine if the octopuses were truly asleep, the team conducted an experiment involving the presentation of a video clip featuring crabs. Ribeiro stated, “Contrary to what you might expect, when we stimulated the animals with visual or vibrant stimuli, they did not react.”
Heidi, the octopus featured in the video, transitions from a beautiful white color to a deep, dark violet before transforming into a fully camouflaged pattern. However, Heidi is not the only sleeping octopus documented to undergo color changes. In October 2017, Rebecca Otey, an intern at the Butterfly Pavilion invertebrate exhibit, filmed a sleeping Caribbean double-point octopus exhibiting similar color transformations.
Video Credit & More info: Nature on PBS