A recent study may prove marine invertebrates such as octopuses are capable of having both dreams and nightmares.

One morning, when researchers from Rockefeller University in New York City arrived at their lab, they discovered a male Brazilian reef octopus with his arms wrapped around a piece of PVC pipe, as if he were trying to strangle it. As well as the creature's strange behaviour, researchers noticed the tank's water was discoloured, so out of curiosity the team looked at the day's camera footage.

They were astonished by what they saw: the octopus seemed to awaken from his nap and began to act defensively before inking his tank.

The study — which has not yet been peer-reviewed — was done on a male octopus named Costello that lives at the university. He was captured a few years ago off the coast of Brazil and moved to his tank.

For three months, cameras tracked Costello's every move, 24 hours a day, seven days a week. He frequently changed colours and patterns while he slept, which led scientists who were watching the video to conclude that he was "dreaming and physically reflecting the contents of its dream through its body language."

But on some footage, the scientists saw that Costello would sometimes startle awake, flail his arms, and spray ink, much as he would in the wild if he were trying to flee a predator.

“The behavioral sequences displayed by this octopus upon emerging from disturbed sleep were similar to behavioral responses to nightmares, night terrors, and other parasomnias in humans, with a narrative structure resembling waking defense behaviors in octopuses,” the authors of the study explained.

“We speculate that the complex behavioral sequences displayed in these episodes suggest octopuses experience parasomnias which may include nightmares with the potential to disrupt their sleep.”

This study is important as octopuses are considered to be one of the most intelligent animals on the planet and play a significant role in the ecosystem. They have a large brain-to-body ratio, which is similar to that of other intelligent animals such as primates and cetaceans.

They also have a complex nervous system and are able to learn and solve problems. In addition, octopuses are apex predators who keep populations of other animals in check, which helps to maintain a healthy ecosystem.

Since the study only looked at the solitary octopus, it is not possible to say whether this behaviour affects all of them, let alone other cephalopods. However, given their intelligence, it isn't hard to believe that octopuses do indeed have dreams about good and bad things, just as we do.