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Science

Spiders Seem To Have REM-Like Sleep and May Even Dream (scientificamerican.com) 49

Posted by BeauHD from the never-before-observed-in-arachnids dept.
An anonymous reader quotes a report from Scientific American: Barred from her lab by pandemic restrictions, behavioral ecologist Daniela C. Robler caught local jumping spiders and kept them in clear plastic boxes on her windowsill, planning to test their reactions to 3-D-printed models of predatory spiders. When she came home from dinner one night, though, she noticed something strange. "They were all hanging from the lids of their boxes," says Robler, a postdoctoral researcher at the University of Konstanz in Germany. She had never seen jumping spiders suspended motionless on silk lines like this before. "I had no idea what happened," Robler says. "I thought they were dead." It turns out the jumping spiders were simply asleep -- and that Robler had discovered an alternate sleeping habit of the species Evarcha arcuata, which had been known to build silk sleeping dens in curled-up dead leaves. But the real surprise came when she decided to spy on them all night. [...]

Mostly the spider just hung there. But then her legs started to twitch, and her abdomen and even her silk-producing spinnerets did so as well. Sometimes her legs curled in toward her sternum. With every spider Robler recorded, these odd movements only appeared during distinct bouts that lasted a little more than a minute and occurred periodically throughout the night. "They were just uncontrollably twitching in a way that really looked a lot like when dogs or cats dream and have their little REM phases," she says. [...] Robler and her colleagues wondered if the twitching spiders could be experiencing something like an REM phase of sleep and possibly even having dreams. "We were like, 'Okay, that would be insane,'" she says. Then she thought, "Let's figure it out," and immediately changed her research plans for the spiders.

[...] When Robler recorded 34 sleeping spiderlings, she found that their twitches were accompanied by unmistakable eye-tube movements that did not happen during other phases of sleep. [...] But it is too soon to say for sure that the spiders are experiencing something akin to REM sleep in humans. The researchers first need to confirm the spiders are actually asleep during this phase by showing that they are less responsive to their environment. Robler and her "dream team" of co-authors have already started those tests. And she points out that the leg curling is a particularly striking aspect of the spiders' REM-like phase because that pose is typically only seen in dead spiders. Spiders use hydraulic pressure maintained by muscles to keep their legs extended, and the curling could result from the muscle paralysis that typifies REM sleep. The team's initial findings were published in Proceedings of the National Academy of Sciences USA.
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Spiders Seem To Have REM-Like Sleep and May Even Dream More

Spiders Seem To Have REM-Like Sleep and May Even Dream

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  • I mean, it's arguable whether you should even refer to their small cluster of somewhat specialized nerve cells as a brain.

    • Re:Hard to believe (Score:4, Interesting)

      by JanSand ( 5746424 ) on Wednesday August 10, 2022 @12:33AM (#62776678) Homepage
      As someone who has had multiple dreams almost every night throughout a very long life, I have tried to figure why my nervous system indulges in this exercise and have come to the conclusion that the process of dream fantasies is an extension of the same processes we practice when being awake. Our nervous system captures experiences as associative packages of patterns of sense input which are stored as memories, Our minds must continually guess which patterns represent useful representations of the limited reality we are capable of realizing that are fundamentally necessary to survive and prosper. When awake, these guesses at reality can be tested for correctness continuously. When asleep, our nervous system utilizes memorized experiences to fabricate wild variations of reality which are our dreams and experience these variations to give us some grasp of what might happen if these fictions might be real. Immense joys and horrors are experienced safely to test our fabrications of reality with no way to test them as actual, but they are valuable in establishing an emotional continuum of possibility. Whatever nervous system a spider might have might have similar processes active in their minds.

      • Re:Hard to believe (Score:5, Interesting)

        by sg_oneill ( 159032 ) on Wednesday August 10, 2022 @01:49AM (#62776728)

        Heres what I SUSPECT is going on (and this does match much of the current thinking on the mechanics of dreaming), and its that is they are a by product of how we process signals and the Shannonâ"Hartley theorem (Roughly that rate of signal transfer, the noise floor and the amplitude are intrinsically linked in a channel)

          As an analogy, think of a modern digital camera. When theres lots of light, the aperature restricts, and the sensor (or whatever) starts pulling back on its sensitivity. As the light decreases, the aperature widens, and the sensitivity goes way up on the sensor. Eventually with low enough light, the aperature is at full width but all the sensor is picking up is electrical noise. At full light, the signal is strong enough to overpower any noise, but at low or no light, that noise starts taking over until its the majority of the signal.

        Neurons work similarly. Highly simplified buy roughly they have a bunch of inputs, and then they basically multiply them with a bunch of weightings and output the result out the end of it. If the signals are strong, they increase the threshold for firing and the weighting of those inputs, but if the signals are all week that threshold drops away and it only takes a tiny signal for that input to triger the gate potential and fire.

        Now the brain is filled with noise. Transient electrical currents, stray neurotransmitter molecules just kinda floating around the brain (it should be observed that SSRIs can ramp the hell out of dreaming, here) and so on.

        Basically theres a lot of noise in the brain, and when you go to sleep, the brain blocks signals from the senses meaning all these sensory signal processing channels have lots of noise in them, and when you cut the signal, noise starts to dominate them, and when you have neurons the first thing those little guys are gonna want to do is find patterns in them (Much in the same way image generation and "deep dreaming" algorithms in neural networks make surrealistic imagery out of noise).

        So basically yeah, viewed that way as a system of signals following basic signal physics, it would be wierd if a brain didnt dream. In fact it would seem evolutionarily it would be more efficient to deal with dreams generating gibberish by denying them access to long term memory and paralysing the body, then it would be to "design" dreams out of the system.

        And thus we behold surrealist vistas at night once the light goes out.

        • Fascinating at your effort to generate emotional aggression. My effort at figuring out the practical approach to explain the mechanics and utility of dreaming and how it might relate to the functional actions of a brain awake is taken as an attack on intellectual effort. I wonder why the fierce reaction to my attempt to understand something created such a negative posture. I certainly have no ambitions to establish any intellectual altitude for my curiosities.

          • Re:Hard to believe (Score:4, Interesting)

            by AleRunner ( 4556245 ) on Wednesday August 10, 2022 @04:50AM (#62776864)

            Fascinating at your effort to generate emotional aggression.

            I don't think you should take it like that. There's always a certain "emotional aggression" in science because true science only happens when someone is wrong and some theory gets excluded. Humans seem to be bad at being wrong and often don't take it well, but it's actually a good thing. You both put forward scientific theories - things that could be wrong and could be properly tested. In your case, for example, by showing that people who can't dream have damaged emotional development and in sg_oneill's case maybe by showing that spider dreams are a form of parallel evolution.

            The funny thing is that you could both be right in some sense. Maybe dreams started as a way of dealing with system noise and have now adapted in humans to help some kind of development. Maybe spiders only have the random dreams and don't deal in emotions? Maybe dreams will be the way that we show that parallel evolution has made emotions in jumping spiders?

            • My thoughts on the matter, just as any thoughts on any matter, may or may not have scientific relevance. Not being a scientist, I cannot say. All I can hope is that the procedure I proposed may be useful and universal enough to apply to any sort of functional approach to a form of life attempting to survive, whether or not it is involved with a nervous system. A recent study reported at https://www.washingtonpost.com... [washingtonpost.com] seems to indicate that various forms of life can act intelligently and even a slime mol

            • Re: (Score:3)

              by La Gris ( 531858 )

              Not only that, but dreaming is part of the learning process and all living entities, even without a nervous system, do have some kind of memory.

              A nervous system, be it very primitive and limited, is still a very advanced memory and processing system (if you compare with plants for example, even though plants don't have neurons, they do have some systems to memorize and interact with the world)

              Now for species with a nervous system of neurons and especially for predatory species. There is need for fast decisi

              • all living entities, even without a nervous system, do have some kind of memory.

                You're going to have to first define memory to support that.

                Start with how it applies to the archaebacteria.

                • Re: (Score:3)

                  by La Gris ( 531858 )

                  all living entities, even without a nervous system, do have some kind of memory.

                  You're going to have to first define memory to support that.

                  Start with how it applies to the archaebacteria.

                  This is why I mentioned they have some kind of memory, because this surely vary in proportional complexity and for the type of living entity.

                  Archaebacteria is close to the edge of what we commonly define as living with viruses and prions. Are prions alive?
                  With that all proportion of memory may differ by definition.

                  As a software person I'd define memory for a living as the capability to change part of its internal state from interactions feed-back. Keep this internal state over time, and have newer interacti

          • Its a little hairier now, but thanks to our high vacciation rate were not seeing the higher infection rates reflected in high hospitalization rates.

            Huh? Am I missing a hidden post or something? Who's trying to generate "emotional aggression?

      • Good comment, this is the kind of thinking I come here to find still.

        Thank you.

        • No. Thank you for being passionately interested. I usually write crazy stuff like this. Linguistobalistics Two B or knot can be questionable Or forgot in quizzy exploration since, As existence goes it is philosophically A pose theoretically most probable. To tear apart the simple there from here Is the standard exercise where elementary Reductions leave one on a stair that, Most frequently, goes up to nowhere. But, admissively, nowhere is always Ubiquitous, a locational fuss of then and thus. . In quantu
    • The bigger question here is: are they psychic? I feel like we need to create a thick-walled sleep study chamber, tell the researchers they're checking for orgonite effects or something with a bunch of hippy volunteers, but actually have millions of jumping spiders in little boxes with lighting designed to trigger their REM sleep cycle at roughly the same time. Have the subject of the study go in to sleep, wired up to determine when they are dreaming, then click the switch to flip the millions of spiders i
    • Spiders say the same thing about you.

    • I think it's quite interesting since that would put the genetics of sleep back in the evolution quite a bit.

      When did sleep evolve?

      • When did sleep evolve?

        Because the simlation can't keep all of us up and running at the same time.

    • Seems much more workable than a misplaced, badly malformed, and dyspeptic liver, as far as brains go.

    • Re: (Score:2)

      by gweihir ( 88907 )

      Well given what spiders can do complexity-wise, that dismissive comment seems not very much connected to reality. Spiders seem to be at 100k braincells and probably around 10M synapses.
       

  • Jumping Spiders Are Not Average Spiders (Score:5, Informative)

    by FeltLion ( 1289024 ) on Wednesday August 10, 2022 @12:11AM (#62776654) Journal
    To reach the food, the spider had to crawl down the tower onto a platform, and then cross one of two pillars leading to separate suspended walkways â" one to the food and one to the leaves. To make the course more challenging, once the spider started its descent down the tower, the researchers emptied the boxes to remove the spiderâ(TM)s visual reminders of where the food is located. Amazingly, each species of jumping spider completed the obstacle course extremely well and made it to the box containing the food, according to the study published in the Journal of the Experimental Analysis of Behavior. Even if the spider chose the wrong path, it paused and seemed confused. âoeTheir expectations for what they were going to werenâ(TM)t met,â said Cross to National Geographic. âoeIt wasnâ(TM)t part of their plan.â The results of the paper seem to indicate that jumping spiders demonstrate âoegenuine cognition.â In other words, they think before they act, and when their plan doesnâ(TM)t work out, they adapt and take a detour. http://thescienceexplorer.com/... [thescienceexplorer.com]

    • Re:Jumping Spiders Are Not Average Spiders (Score:5, Interesting)

      by systemd-anonymousd ( 6652324 ) on Wednesday August 10, 2022 @12:19AM (#62776668)

      I saw a beetle dragging a dead spider across my driveway. It dropped it, flew about 20 feet away, then came back to the area and circled around, apparently looking for where it left the spider. It found it again and then resumed laboriously dragging it, now more in the direction of where it had flown and landed. I found it amazing that this beetle had a task, short term memory, flew around to better find the direction to its destination, then returned and refined the direction it was dragging the corpse. This also was taking many minutes to do.

    • Interesting. Also interesting is that apparently almost all slightly complex species need sleep, and that if they exhibit anything more than just instinct, they also have REM sleep. That means it's a really really basic process.

      To bad we still don't know much about sleep or REM sleep, despite decades of study.

      • "Just instinct" is a lot more complicated than you suggest. The spider needs to build a world model to navigate in, and have notions like "friend", "enemy", "victim", "food", etc.

        • Re: (Score:1)

          by Anonymous Coward

          Notions can be approximated without cognition. Beetles try humping beer bottles (till starvation iirc) because they "identify" with simpler hard-wired means. Instinct. Pre-programmed with designs that can be "stacked into the deck" of DNA and grown in, not conclusions assembled during lifespan.

          Animals that can store and analyze memory are likely to have advantage in many (not all) scenarios, at a cost. One cost is probably sleep. You can approximate notions without sleep. An ant can do mapping, but it might

  • Spider REM. (Score:5, Funny)

    by The Evil Atheist ( 2484676 ) on Wednesday August 10, 2022 @12:18AM (#62776664)
    That's it in the corner.

  • Spiders dream of sheep flies ?

  • than seeing a spider running in their sleep like a dog.

  • "Look Ma, I invented the World Wide Web!"

    Ma: "Don't be silly, this is only a dream. Now wake up son..."

  • Itâ(TM)s not Robler. It should be spelled Roessler. Probably pronounced a bit like English âoewrestlerâ. The umlaut o is oe and the ÃY is ss.

  • Oh, wait, wrong kind of spider, nvm.

  • Now we know why everyone thinks they are creepy.
    Good to know if they are itching and twisting: they are just sleeping and you can smash them!

  • Well, they sure have eyes enough to rapidly move. Also way too many legs.
  • Now they should interrupt the presumed REM sleep and see if the result conforms to that of higher animals whose REM sleep has been disturbed.

  • they are not dreaming, but entering dreams to torment us

  • Daniela might want to see a doctor about that.

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