The ecstatic octopus

Looking back, there are many examples of scientists giving recreational drugs to animals. Usually, these have consisted of giving a psychedelic drug (such as LSD) to a subject, be it cat, rat, dog, dolphin, fish, or elephant. The aim of these studies was to test how the animal responded and the psychological effects induced by psychedelics. There are not many incidences of administering an illegal substance to an animal to study evolutionary biology. Recently, however, Eric Edsinger and Gül Dölen, from John Hopkins University in Boston, did just that.

In a paper published in Current Biology (Cell Press) this month, the authors detail experiments in which they administered (+/-)-3,4-methylenedioxymethamphetamine (MDMA or ‘ecstasy’) to a group of unsuspecting octopi.

Much to the delight of the researchers, and those who have read about it, the cephalopods responded to the drug in a manner that is equivalent to the human response. Usually antisocial, solitary creatures, the subjects increased social interaction and touching – even putting their mouthparts against the cage containing another of their species. These ‘entactogenic’ (these are drugs that induce feelings of emotional openness and empathy) properties were common to all the test animals. Unfortunately, the other stereotypical MDMA response of an increase in locomotor activity was not replicated–there were no gurning octopi who flailed their eight limbs around.

As fun as the study sounds, there was a more important point than watching octopi trip. In humans, MDMA acts upon serotonin transporters in the brain, which leads to the intense feeling of happiness and an increase in social behaviour. This study demonstrated that, despite their brains being more similar to a snail’s than a human’s, the octopi have serotonin receptors that are similar enough to be stimulated by the same drug.

The paper further confirmed the similarities with whole-genome sequencing. Octopi are invertebrates and their lineages separated from humans roughly 500 million years ago. Having a neurological pathway in common, despite several hundred million years of evolution, gives an incredible insight into developmental history. The paper suggests that the serotonin transporters may even have had an ancient role in nervous system centralization and formation. This is big news in the world of evolutionary biology.

In addition to the evolutionary side, the study gives an insight into the social interactions of a very antisocial animal. In the natural world, octopi will only abandon their solitary lifestyle to mate, immediately recovering their unfriendly attitude as soon as the deed is done. Edsinger and Dölen theorise that the serotonin pathways may be suppressed and lie dormant until a mating opportunity presents itself. It is triggered long enough for a pair of octopi to make the beast with two backs (and 16 legs) and then return to dormancy post-coitus. As they aren’t the easiest animal to study, providing an understanding of their psychology and lifestyle is an exciting addition to the study.

As ridiculous as a scientific paper about tripping octopi sounds, the insights gained by the study are numerous. It is possible that studies such as these will continue, trying to elucidate exactly where in the evolutionary tree is the point that serotonin transporters stop being part of an animal’s neurological makeup. So, watch this space – there could be an article about tripping starfish next.

 

Image Credit: cocoparisienne via Pixabay

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