Does this octopus have a nightmare?

Costello the octopus slept while attached to the glass of his tank at Rockefeller University in New York. He slumbered peacefully for half an hour and then entered a more active sleep phase, his skin cycling through colors and textures used for camouflage – typical behavior for a cephalopod.

But soon things got strange.

A minute later Costello raced past the glass to the sand bottom of his tank, his arms curled over his body. Then it spun around like a twisting cyclone. Finally, Costello dove down and fogged up half his tank with ink. As the tank’s filtration system cleaned up the ink, Eric Angel Ramos, a marine scientist, noticed Costello gripping a pipe with unusual intensity, “it looked like he was trying to kill it,” he said.

“This was not normal octopus behavior,” said Dr. Ramos, who is now a student at the University of Vermont. It’s not clear when or if Costello woke up during the episode, Dr. Ramos. But after that, Costello returned to normal, eating and later playing with his toys.

“We were completely dumbfounded,” said Marcelo O. Magnasco, a biophysicist at Rockefeller. Perhaps Costello was having a nightmare, he and a team of researchers speculated. They shared this idea and other possible explanations in a study uploaded to the bioRxiv website this month. It has yet to be formally reviewed by other scientists.

After the incident, Dr. Ramos captured the footage of Costello’s activity, which was recorded as part of a behavioral and cognition study (the lab also observed another octopus, Abbott; both are named for the heptapod aliens in the movie “Arrival”). In total, the team found three more shorter specimens that resembled each other.

For dr. Magnasco, the behaviors displayed during Costello’s longest spell evoked the acting out of a dream. Curling the arms over his body resembled a defensive stance, he said. The footage shows that the animal may be trying to make itself look bigger, and then it tries an evasive maneuver – inking. When he fails to escape, it appears Costello is trying to quell a threat by strangling the pipe, Dr. Magnasco, adding, “This is the order of battle.”

But he also acknowledged that “this is an isolated case of an animal with its own idiosyncrasies.”

There are other explanations for the behavior, such as a seizure or neurological problems, that could be related to Costello losing parts of two limbs before being caught. But dr. Magnasco said he hoped that by reporting the incident, other scientists would watch out for the behavior his group observed by chance.

Tamar Gutnick, a neuroethologist at the University of Naples Federico II in Italy who was not part of the study, said the researchers had to answer questions in peer review, such as a question about what happened around the same time the next day. Her colleague at the same university, Michael Kuba, a marine behavioral biologist, also told them to describe Costello’s typical sleeping behavior.

The study’s researchers said they could explain such questions since they have images of the octopus’s entire life in the lab.

Another problem in interpreting this octopus’s behavior, said Dr. Kuba, is that Costello “wasn’t completely sane and healthy”: the animal had stomach parasites.

Dr. Kuba suggested that some behaviors, such as curling the arms, could be due to cramps, perhaps due to a problem with Costello’s digestive system or due to the parasites reaching part of his nervous system. Similar behaviors occur in captive octopuses, and they’re usually related to stress or age, he said. Costello died about six weeks into the longest episode.

Still, the idea of ​​dreaming in octopuses is compelling, said Dr. Gutnick. The Rockefeller team isn’t the first to propose the idea that cephalopods dream as they go through different stages of sleep. Because octopuses’ body patterns are controlled by the brain, researchers have wondered if patterns during sleep could be responses to a dreamlike repetition of events.

In their own research, Dr. Cuba and Dr. Gutnick recently received electrical signals from the brain of an octopus. That opens up the possibility that researchers could spy on octopuses’ brain activity during sleep, and perhaps connect behaviors and body patterns during sleep with brain wave shifts to study processes related to dreaming.

But that’s not necessarily related to this observation, said Dr. Gutnick, adding, “You have to show them they have dreams before you think about nightmares.”