22 September 2018

Giving octopuses ecstasy

California two-spot octopus (Octopus bimaculoides)Nobody told me it was “Drug an invertebrate week.” But not only has a story of lobsters getting pot rather than going into pots made the round, now we have octopuses getting another recreational human drug. The story, according to headlines, is that giving ecstasy (MDMA) to octopuses makes them act more socially. And everyone’s comparing octopuses to ecstasy fueled partygoers at a rave.

It’s a nice narrative, but there isn’t enough evidence to conclude that.

There is some genetic analyses of MDMA receptors in this apaper, but all of the interest in the press is about the behaviour experiments. The authors gave the octopuses the drug. The octopuses’ behaviour changed. The popular press is interpreting that behaviour in a cutesy way, using terms like “hug” and “cuddle” in headlines. (Even publications like Nature who should know better.)

That’s a problem. Octopuses hunt prey by enveloping them with their web and tentacles — effectively “hugging” them, if you will. Being eaten is rather different than cuddling. The authors provide no videos in the paper, just two still images (below), so you can’t see the behaviour in detail.

Photograph of Octopus social interaction under the saline condition on left and MDMA condition on right.

The sample size for the behavioural experiments is 4 or 5, as far as I can see. That’s tiny.

It’s worth noting that the behavioural changes were not always the same.

In addition, pilot studies in 3 animals indicated that higher submersion doses of MDMA (ranging from 10-400 mg/Kg) induced severe behavioral changes (e.g., hyper or depressed ventilation, traveling color waves across the skin or blanching, as well as catatonia or hyper-arousal/vigilance) and these animals were excluded from further analysis.

Dose-dependent responses are not at all unusual, but again, it makes the simple story of “MDMA means social” more complicated.

I do appreciate that this paper has an Easter egg for people who read the methods:

Novel objects consisted of multiple configurations of 4 objects: 1) plastic orchid pot with red weight, 2) plastic bottle with green weight, 3) Galactic Heroes ‘Stormtrooper’ figurine, and 4) Galactic Heroes ‘Chewbacca’ figurine.

But which Stormtrooper, people?


Which Stormtrooper?!

The paper is interesting, but it’s not getting attention from popular press because it’s particularly informative about the evolution of social behaviour. It’s getting attention because of the novelty of giving drugs to animals, and the “Oh look, animals are like us!” narrative.

Additional, 24 September 2018: Another interpretive problem. Normally, in an interview on CBC’s Quirk and Quarks, Gul Dolen notes octopuses overcome their asocial behaviours for mating. Dolen cites this as reason to think that there could be a way to “switch” the octopuses’ behaviour using a drug. So mating behaviour is the natural “social” mode for these animals.

But the octopus under the basket was always male, because the researchers found octopuses avoided males more than females.

Three of the four octopuses tested were male. (I had to dig into the supplemental information for that.) So most of the observations were male-male behaviour. I don’t know that homosexual behaviour has ever been documented in octopuses. A quick Google Scholar search found nothing.

A Washington Post story revealed that the authors’ wouldn’t even talk about some of the behaviours they had seen:

The authors observed even stranger behavior that they did not report in the study, Edsinger said. He was reluctant, even after extensive questioning, to further describe what the octopuses did, because the scientists could not be sure if the MDMA had induced these actions.

This is problematic. This suggests the behaviours in the paper are deeply underdocumented at best. And it seems to be done on purpose, because it doesn’t fit the authors’s narrative. This, combined with the description of behaviours at different doses, it further suggests that rather than “prosocial” behaviour that the authors and headlines are pushing, the exposure to MDMA is making octopuses behave erratically, not socially.

Reference

Edsinger E, Dölen G. A conserved role for serotonergic neurotransmission in mediating social behavior in Octopus. Current Biology: in press. https://doi.org/10.1016/j.cub.2018.07.061

External links

Octopuses on ecstasy: The party drug leads to eight-armed hugs
This is what happens to a shy octopus on ecstasy
Octopuses on ecstasy just want a cuddle

Picture from here.

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