The remarkable distributed nervous system of the octopus is discussed at an astrobiology conference.
- Unlike vertebrates, two-thirds of an octopus' neurons are in its tentacles.
- Tentacles respond to the surrounding environment without help from the head's brain.
- If something this weird is here on our own Earth, what could be out there in space?
The decentralized octopus nervous system<p>Sivitilli's emphasis is not on, "How intelligent are they?" he says, speaking to <a href="https://www.washington.edu/news/2019/06/18/of-octopuses-and-astrobiology-conference-talk-speculates-on-cognition-beyond-earth/?utm_source=UW%20News&utm_medium=tile&utm_campaign=UW%20NEWS" target="_blank">UW News</a>. "We are asking, '<em>How</em> are they intelligent?'" It's clear that "Their way of thinking is fundamentally different," representing "an alternative model for intelligence." He concludes that the octopus "gives us an understanding as to the diversity of cognition in the world, and perhaps the universe."</p><p>Though no one would claim the finer workings of our own human central nervous system are simple, its rough architecture at least — something we share with other vertebrates — seems pretty straightforward. There's the brain full of neurons to which receptors throughout our bodies provide information. The neurons process, interpret, store, and develop responses to the information, and the brain sends out signals that control our physical movements.</p><p>The cephalopod octopus nervous system is something else entirely. 350 million of its 500 million neurons are in its eight tentacles. At the tentacles' surface are many thousands of chemical and mechanical receptors. The octopus brain appears to offload interpretation of those inputs, decision-making, and even control of the tentacles <em>to</em> the tentacles, potentially allowing the cephalopods to react to multiple events and circumstances simultaneously. Sivitilli says, "When I do my work, I look at how the arms are acquiring information from the environment, and how they are collectively making decisions about that information."</p><iframe width="560" height="315" src="https://www.youtube.com/embed/6laZ9ad-D54" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
A different path to intelligence<p>The neurons of our central nervous systems are organized around a spinal cord and column, but the cephalopod nervous system coalesced from neurons collected in ganglia distributed throughout the body.</p><p>Sivitilli's advisor neurologist David Gire shares in a <a href="https://news.agu.org/press-release/researchers-model-how-octopus-arms-make-decisions/" target="_blank">conference press release</a>, "One of the big-picture questions we have is just how a distributed nervous system would work, especially when it's trying to do something complicated, like move through fluid and find food on a complex ocean floor. There are a lot of open questions about how these nodes in the nervous system are connected to each other."</p><p>One of the known mechanisms is a neural ring that allows the tentacle neurons to exchange information directly, bypassing the brain. "So while the brain isn't quite sure where the arms are in space," says Sivitilli, "the arms know where each other are, and this allows the arms to coordinate during actions like crawling locomotion."</p><p>His conclusions are based on laboratory research in which he and his colleagues gave octopuses challenges to overcome, in addition to observing them look for food in their tanks. According to Gire, "You're seeing a lot of little decisions being made by these distributed ganglia, just by watching the arm move, so one of the first things we're doing is trying to break down what that movement actually looks like, from a computational perspective."</p><iframe width="560" height="315" src="https://www.youtube.com/embed/h6cy46G8u3g" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
The story of Gaia<p>Sivitilli has written movingly in "<a href="https://psych.uw.edu/newsletter/winter-2018/graduate-program/across-the-evolutionary-divide-the-story-of-gaia" target="_blank">Across the Evolutionary Divide: the Story of Gaia</a>" about his experience, and relationship, with one particular octopus, a giant Pacific octopus, or <em>Enteroctopus dofleini</em>, whom he named "Gaia."</p><p>He describes the eerie moment they met, and their first impressions of each other. After weeks of diving in the dark, he says, "45 feet below San Juan County Park, my dive team at last methodically encircled a large, camouflaged, breathing mass, as it watched us intently." After transporting her back to his lab, things didn't get any less strange:</p><p>"Nightfall and finally alone in a quiet, dim lab, I felt my movements being watched. I sat facing my new model, observing her as she continued to fix her gaze upon me. About five feet separated the tips of her opposite arms when she reached them outward — she was young, yet, she seemed so old, reaching out to me from deep evolutionary time."</p><p>Gaia was eventually returned to the sea, leaving Sivitilli, it seems from his writing, with a feeing of profound connection:</p><p><em>"</em>Perceptive, curious, and above all, distant, Gaia manifested everything to me that makes the octopus model so attractive. Two cousins we are, meeting across the evolutionary divide of over 500 million years.<em>"</em></p><img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTYzMTM3MS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY1MDc3NDU1N30.ufN5B8T6YyKb_7EHwVvx6uSMZ6vI1jKhBo1hTuXVYEk/img.jpg?width=1245&coordinates=167%2C0%2C95%2C0&height=700" id="fc6b5" class="rm-shortcode" data-rm-shortcode-id="7a7a18e126ea5cfdebd58013074d482b" data-rm-shortcode-name="rebelmouse-image" />
Gaia in her first and second tanks
Image source: Dominic Sivitilli
A groundbreaking new study shows that octopuses seemed to exhibit uncharacteristically social behavior when given MDMA, the psychedelic drug commonly known as ecstasy.
- Octopuses, like humans, have genes that seem to code for serotonin transporters.
- Scientists gave MDMA to octopuses to see whether those genes translated into a binding site for serotonin, which regulates emotions and behavior in humans
- Octopuses, which are typically asocial creatures, seem to get friendlier while on MDMA, suggesting humans have more in common with the strange invertebrates than previously thought
A crucial difference<p>Despite this cognitive sophistication, many scientists have long thought octopuses and other invertebrates <a href="http://jeb.biologists.org/content/220/21/3856" target="_blank">lack the neural requirements needed to experience emotion</a> or practice social behaviors in the ways mammals do.<br></p><p>However, a new study published in the journal <a href="https://www.cell.com/current-biology/fulltext/S0960-9822(18)30991-6?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0960982218309916%3Fshowall%3Dtrue" target="_blank"><em>Current Biology</em></a> challenges that long-held presumption by showing that administering MDMA to octopuses seems to elicit social behavior in them, suggesting that the architecture for experiencing such phenomena extends farther back in evolutionary history than previously thought.</p><p class="caption">For the study, the researchers devised an experiment in which they placed a California two-spot octopus in a tank containing three rooms separated by two walls with slots. The middle room was empty, but the two rooms on either side contained either a "novel toy object" (a stormtrooper figurine) in a cage or another octopus in a cage, and the non-caged octopus was free to spend time in whichever room it liked. </p><p>All five of the octopuses that completed this part of the experiment spent far more time in the room with the toy, though both male and female octopuses did tentatively explore the other room when a female was in the cage.</p><p>The researchers then conducted this experiment again, but this time, each octopus was bathed in water containing MDMA before entering the three-zone tank. Unlike before, the octopuses on MDMA seemed far more interested in the room with the octopus, at times touching it in an exploratory manner, instead of the room with the lifeless toy.</p><img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xODY0Njc4Ni9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxNTkyMDk0Nn0.3NfTjNslw5jLDOe9Xi7Eg2Bx14o8akraeJT4y4bR1PU/img.jpg?width=980" id="feaa1" class="rm-shortcode" data-rm-shortcode-id="51f68b5636ec6f58e61f409dda630c90" data-rm-shortcode-name="rebelmouse-image" />
The three-zone tank used in the experiment. Cage with toy on left, cage with octopus on right.
(Eric Edsinger, Gül Dölen)
An eight-armed hug<p><a href="http://neuroscience.jhu.edu/research/faculty/23" target="_blank">Gül Dölen, Ph.D.</a>, an assistant professor of neuroscience at Johns Hopkins University and co-author of the study, told <em><a href="https://www.inverse.com/article/49157-mdma-octopus-serotonin-study" target="_blank">Inverse</a> </em>it was like watching an "eight-armed hug."</p><p>"They were very loose," Dölen said. "They just embraced with multiple arms."</p><p>It's impossible to know what the octopuses were experiencing, but Dölen offered her own personal observation (as anecdotal evidence, not scientific) to <em>Inverse</em>: the octopuses acted like humans do when they're on ecstasy. </p><p>On high doses, the octopuses breathed intensely and turned white. But on lower doses, the octopuses seemed to display more typical behavior of someone on a psychedelic: one became very interested in minor sounds and scents, another spent some time doing flips in the tank, and one octopus "looked like it was doing water ballet," swimming around with its arms extended.</p><p>In humans, MDMA acts on the brain mainly by stimulating activity of the neurotransmitter serotonin. The California two-spot octopus also possesses a serotonin transporter to which MDMA can bind. However, the researchers weren't sure whether this ancient feature was active in the octopuses.</p><p>"We needed to check the 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 octopuses even despite the fact that so much evolutionary time had passed," Dölen told <em>Inverse</em>.</p><p>"We performed phylogenetic tree mapping and found that, even though their whole serotonin transporter gene is only 50 to 60% similar to humans, the gene was still conserved. That told us that MDMA would have a place to go in the octopus brain and suggested it could encode sociality as it does in a human brain."</p><img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xODY0NjgwMC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYyMzkyNTU3N30.1aAKb1cucZzOl2QLLgCZ6s1l4b1vndI3bMDtqDL948Q/img.jpg?width=980" id="b047d" class="rm-shortcode" data-rm-shortcode-id="9673e8644a6d00c84b748bc3aff3c082" data-rm-shortcode-name="rebelmouse-image" />
Although they are about as alien from human life as it gets, Dölen's study shows that octopuses share some important characteristics with humans.
(FRED TANNEAU/AFP/Getty Images)
Familiar behavior in strange brain structures<p>The idea that octopus behavior might be regulated by serotonin, which largely controls human emotion, is especially interesting because of how different the creatures are from humans.</p><p>"This was such an incredible paper, with a completely unexpected and almost unbelievable outcome," said Judit Pungor, a postdoctoral researcher at the University of Oregon not involved in the study, in an interview with <a href="https://gizmodo.com/scientists-gave-mdma-to-octopuses-and-what-happened-was-1829191638" target="_blank"><em>Gizmodo</em></a>. "To think that an animal whose brain evolved completely independently from our own reacts behaviorally in the same way that we do to a drug is absolutely amazing."</p><p>To be sure, it's not exactly clear why the octopuses "opened up" while they were on MDMA. In addition to the study being limited by sample size, it's possible that the octopuses were more inclined to touch the other octopus because the drug made them more interested in touching in general, not necessarily social touching. </p><p>Still, Dölen said that the findings suggest that molecular and cellular genetic information, rather than anatomical data, are more important in deciding whether animals develop social behavior.</p><p>"Octopuses don't have the same parts of the brain that we think are important for social behavior, a region called the nucleus accumbens," Dölen told <em>Inverse</em>. "What we're arguing is that the brain regions don't matter. What matters is that they have the molecules, the neurotransmitters, and some configuration of neurons. They have the serotonin transporter and that's enough."</p>
There’s a special reason these generally solo cephalopods have decided to cohabitate.
If you’ve ever dreamed of visiting an octopus’s garden like the Beatles song portrays, you might get your chance—if you visit Australia. Common Sydney Octopuses, also known as gloomy octopuses (Octopus tetricus) were recently found cohabiting in Eastern Australia’s Jervis Bay, at a depth of 10-15m (30-45 ft.).