This is exactly the kind of setup that neuroscientists use to test social behavior in mice, but Dölen had no idea whether it would work with octopuses. “It might be that they are so smart that the kind of task we’d use for a mouse would be boring to them,” she says. “Maybe they’d take one lap around the chambers and stop.” Fortunately, that wasn’t the case. The free-moving individuals thoroughly explored the chambers, and from their movements, Dölen realized that individuals of any sex gravitate toward females, but avoid males.
Next, she dosed the animals with ecstasy. Again, there’s no precedent for this, but researchers often anesthetize octopuses by dunking them in ethanol—a humane procedure with no lasting side effects. So Dölen and Edsinger submerged their octopuses in an MDMA solution, allowing them to absorb the drug through their gills. At first they used too high a dose, and the animals “freaked out and did all these color changes,” Dölen says. But once the team found a more suitable dose, the animals behaved more calmly—and more sociably.
With ecstasy in their system, the five octopuses spent far more time in the company of the same trapped male they once shunned. Even without a stopwatch, the change was obvious. Before the drug, they explored the chamber with the other octopus very tentatively. “They mashed themselves against one wall, very slowly extended one arm, touched the [other animal], and went back to the other side,” Dölen says. “But when they had MDMA, they had this very relaxed posture. They floated around, they wrapped their arms around the chamber, and they interacted with the other octopus in a much more fluid and generous way. They even exposed their [underside], where their mouth is, which is not something octopuses usually do.”
But most octopuses, with some exceptions, are solitary hermits, and Jennifer Mather from the University of Lethbridge isn’t convinced that ecstasy is making them sociable. Instead, the drug might just mess with their ability to detect the chemical cues of potential mates. “There’s no proof that it is anything more than attraction,” she says.
Harriet de Wit from the University of Chicago, who has studied ecstasy’s effects on animals, has other concerns. “It’s an innovative and exciting study,” she says, but it’s unfortunate that the duo always tested the octopuses first after a dunk in normal salt water and then after an ecstasy bath. In pharmacology studies, scientists normally mix up the order in which animals receive the drug and the saline control. Without that counterbalancing, it’s hard to say why the octopuses were behaving differently the second time around: Was it because of the ecstasy, or simply because they had become familiar with the arena, the plastic toy, or the other octopus?
Dölen admits that the study is just a pilot, and one with a very small sample size. “We would obviously want other people to try and repeat it in a much larger group of animals,” she says. “But we wanted to publish it, because there really aren’t established protocols for delivering drugs to octopuses or doing social tests with them.” She hopes that her findings will encourage more neuroscientists to study these beguiling animals.