Have you ever observed your pets asleep? Witnessed their twitching feet and whiskers, accompanied by occasional yips and mewls? Well, it's commonly known that cats and dogs experience REM sleep, suggesting they may dream. However, have you ever witnessed an octopus in slumber? We've stumbled upon a video featuring an octopus named Heidi, and as she dreams, she undergoes a mesmerizing color-changing phenomenon.
Although there's currently no definitive evidence of REM sleep in octopuses, they do exhibit a unique sleep twitch. Typically, octopuses experience flickering movements during their sleep. When in a relaxed state, neuronal activity in their optic system triggers the activation of chromatophores, the cells responsible for holding pigments. Consequently, the skin of the octopus transitions between various colors and designs while snoozing, almost as if responding to sensations.
Sidarta Ribeiro and his team from the Federal University of Rio Grande do Norte in Natal, Brazil, have identified two distinct sleep stages in octopuses-active and passive. Conducting extensive video documentation of four common laboratory octopuses (Octopus Vulgaris), totaling over 180 hours of footage spanning multiple days and nights, the researchers made intriguing observations.
Ribeiro notes that during more than half of the day the octopuses spent in slumber, they maintained a static position-closed pupils, extreme stillness, a very pale appearance, and almost inaudible respiration. “They remain in the same position for a long time, the pupils have closed, extremely quiet, very pale – and they respire very quietly regularly,” he explained.
This prolonged passive sleep was periodically interrupted every 30 to 40 minutes by a brief episode of active sleep lasting 1 to 2 minutes. During this phase, the octopuses displayed changes in body color and texture, including the emergence of fine skin bumps known as papillae. The creatures' eyes and arms also exhibited movement. Ribeiro describes this phase as notably dynamic, stating, “It's obviously quite busy.”
To assess whether octopuses are truly asleep, the team conducted an experiment involving visual and vibrant stimuli. Contrary to expectations, Ribeiro reported, “If we stimulated the animal with visual or vibrant stimuli, they did not react.”
Heidi, the color-changing octopus in the video, transitions from a lovely white to a deep, dark violet before adopting a full-blown camouflage pattern. Interestingly, Heidi is not the only sleeping octopus documented with such color-changing behavior. In October 2017, a Caribbean double-point octopus was captured on film by Rebecca Otey, an intern at the Butterfly Pavilion invertebrate exhibit.
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