Octopuses can alter the color and texture of their skin in the blink of an eye. Sometimes, they rely on their color-changing capability to conceal themselves from predators and prey alike.
Other times, they communicate their intentions to others of their kind through colorful displays. But recent footage of a sleeping octopus showed that the animal could also change color unconsciously.
First posted on Twitter in 2018, the video starred a Caribbean two-spot octopus (Octopus hummelincki) in a brightly lit aquarium at the Butterfly Pavilion in Westminster, Colorado. The footage got recorded by Rebecca Otey, an intern at the zoo, back in 2017.
Normally, octopuses look for a secluded spot where they might sleep undisturbed. In this rare instance, the octopus felt either safe or tired enough to doze out in the open water.
As it slept, the color of its skin shifted from its normal white to the exact opposite before returning to a light coloration.
The beginning of the clip showed the octopus in a pearly white state. As the seconds ticked by, grey markings formed on its skin in line with its breathing patterns.
Eventually, most of its body adopted a speckled brown color before it returned to its paler scheme. During the entire time, the octopus remained asleep, as evidenced by its tightly shut eyes.
The chromatophores of the octopus are responsible for this and other changes in color. By altering their size through expansion or contraction, the highly developed pigment cells change the colors of the skin and form intricate patterns across the body.
Interestingly, Butterfly Pavilion researcher Sara Stevens pointed out that octopuses happen to be colorblind. Their eyes cannot detect the colors they are trying to copy.
Instead, they have specialized cells called iridophores and leucophores. These structures sense colors on their behalf, and octopuses adjust their chromatophores accordingly.
“The exact processes of how they match colors is still not fully understood, though it's being very thoroughly studied,” Stevens explained in an interview. “But current research suggests that the actual cells themselves can match colors.”
Octopuses and other cephalopods typically changed their coloration in reaction to their environment. Since the octopus in the video was asleep, experts wondered if it dreamed – and if its dream prompted the shift in color.
Researchers have grown more interested in the sleep and dreaming of cephalopods in recent years. A 2012 study by Washington State University (WSU) researchers showed that sleeping cuttlefish displayed rapid eye movement (REM).
In humans, REM sleep leads to dreams. In cuttlefish, this stage of sleep causes the color of their skin to shift at random.
“It's been hypothesized that octopus species can exhibit something very similar to REM cycles in humans — but the jury's still out on whether they're achieving REM sleep,” explained Stevens.
An octopus lacks the central nervous system of vertebrates like humans. Instead, it has large groups of nerve cells in each of its eight tentacles.
These eight “brains” give an octopus incredible control over its body, including its chromatophores. But it seems that the animal doesn't always assume direct control of its color-changing cells.
Researchers like Stevens continue to wonder if these fascinating animals dream. Some even dare hope that octopuses dream of electric-green leaf sheep.