Octopuses are typically antisocial and treat each other with aggression.
Scientists wanted to know whether invertebrate and vertebrate neurotransmitter systems still share some similarities after hundreds of millions of years of evolution.
As a result of testing of the drug revealed the similarity of the biochemical basis of this marine life and humans, which is very unusual for these non-native organisms. "They looked like they were freaked out", Johns Hopkins neuroscientist Gül Dölen told NPR.
It turns out that octopuses and people have nearly identical genes for a protein that binds the signaling molecule serotonin to brain cells. And this hasn't just been observed in humans - mice and rats also want to bond with each other when under the influence. The octopuses then ingested the MDMA through their gills. But after the genome of the California two-spot octopus (Octopus bimaculoides) was sequenced and published, scientists suspected that human and octopus brains may work the same - in one specific way.
One octopus was doing back flips, according to Dr Dolen, who said that some of the behaviours were so odd the research team couldn't quantify them.
"They really didn't like it". So they weren't super-social, but they were more social than they had previously been thought. "They would sit in the corner of the tank and stare at everything".
But lower doses - the sort a person might take - produced a profound change in behavior. Initially, the octopuses loitered more in the tank with the toy with it.
Based on what the scientists said, the goal of this demonstration is to see how serotonin can affect social interaction. "A small lobster given serotonin will become a more aggressive, socially dominant lobster". A similar feature is present also in humans.
This could explain why MDMA has a similar effect on both species.
"An octopus doesn't have a cortex, and doesn't have a reward circuit", Dölen said. The octopus's explored the entirety of the tank before deciding to spend more time around the inanimate object. The research, which, yes, means giving octopuses ecstasy, can definitely be seen by some as a little unethical, but the experts say they make sure to take care of the animals. NPR's Nell Greenfieldboyce has been diving into this important story.
The design of the experiment testing the octopus' interaction with novel objects and other another octopus. Professor Harriet de Wit from the University of Chicago, who has studied how ecstasy affects animals, said it was "innovative and exciting" - but that we can't be certain the drugs were fully responsible. This allowed for comparisons to be made between human and octopus genes.
Scientists gave several female and male octopuses a bath laced with the drug.
DOLEN: And what we did is we put that MDMA in a beaker that had a known volume of seawater in it. They then returned them to the sectioned-off chambered areas in the aquarium. When "high", the octopuses went straight to the caged solitary male. When it comes to the furry character from Star Wars, it seems that the octopuses only spent some time with Chewbacca throughout the control test, when they were not on drugs.
GREENFIELDBOYCE: Without the drug, octopuses acted reserved and aloof and might only reach out one of their eight arms to touch the cooped up animal. Current Biology, Sept. 20, 2018.
While octopuses are intelligent creatures, their brains are physically very differently to those of humans.
"They have this huge complex brain that they've built, that has absolutely no business acting like ours does - but here they show that it does", said Pungor.
ZACHARY MAINEN: Is it really affection? So it's really - it's totally fascinating.