When The Beatles recorded the song “Octopus’s Garden”, they probably imagined a friendly octopus that invited humans to sing and dance around in their underwater garden (in the shade). In reality, however, octopuses are known to be asocial and solitary creatures. While several invertebrates (e.g., bees, ants, and shrimps) and vertebrates (e.g., fishes, birds, rodents) in the animal kingdom display social characteristics, an octopus only suspends its reclusiveness during mating season – indicating a suppression of social behavior outside the reproductive period. Separated by 500 million years of evolution, human beings also display similar emotional characteristics. We tend to enjoy our solitude and inhibitions, occasionally shedding them in pursuit of the opposite gender.
In fact – our mood, social behavior, sleep, and sexual desire are all regulated by the neurotransmitter serotonin. Multiple research into the psychoactive drug 3,4-Methylenedioxymethamphetamine (MDMA), commonly known by its street name Ecstasy, shows that it temporarily enhances the serotonin levels in humans – resulting in increased social behavior and elevated levels of happiness. So how would octopuses, who display similar emotional traits as a human, react under the influence of MDMA?
This was the question that Gül Dölen, assistant professor of neuroscience at Johns Hopkins University, and Eric Edsinger, a research fellow at the University of Chicago’s Marine Biological Laboratory set out to answer. Prior to the experiment, they had to perform a preliminary check on the California two-spot octopus that they selected for the study. “We needed to check it’s genome to make sure that the genes that encode the serotonin transporter, which is the protein that MDMA binds to, was still a binding site in the octopus despite the fact that so much evolutionary time had passed,” Dölen explains. By performing a phylogenetic tree mapping, the researchers found that even though their whole serotonin transporter gene was only 50-60% similar to humans, the gene in itself was still conserved. “That told us that MDMA would have a place to go in the octopus’s brain and suggested it could encode sociality as it does in a human brain”, she said.
The researchers set up the experiment by dividing a salt-water tank into three chambers. The chambers on either end contained an inanimate object and an octopus, both in cages. The control group consisted of five octopuses that were introduced in the center chamber, one at a time. The octopus’s explored the entirety of the tank before deciding to spend more time around the inanimate object. However, the MDMA trial group, consisting of four octopuses, showed significantly different behavior. They spend more time around the octopus in the cage, even spreading their limbs to symbolize “an eight-armed hug.”
“They were very loose,” Dölen says. “They just embraced with multiple arms.”
The researchers concluded from the experiment that, just like humans, MDMA enhanced the acute prosocial behaviors in California two-spot octopuses. They also stated that serotonin was an ancient neurotransmitter, whose function to regulate social behaviors may be conserved across evolution. The findings add evidence to the idea that social behavior has a long evolutionary history – and goes back much farther than researchers ever anticipated. Finally, the results could significantly impact what we know about the evolution of brains and why MDMA-assisted therapy seems to be such a useful tool in treating post-traumatic stress disorder and anxiety.
While there could be alternative explanations for the octopus’s friendliness, the conclusion provided by the researchers seem to be the most robust out of all of them. Octopuses are believed to be Earth’s first intelligent beings, and the study could kick-start research of linking intelligence with anti-social behavior. Nonetheless, an octopus under the influence of MDMA is very likely to invite you into their underwater garden, while singing and dancing to The Beatles.