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Scientists discover the first brainless animal that sleeps
- Khanthulhu 9y agoTitle is technically correct (the best kind of correct) but jellies do have a nervous system. Its a net if a few hundred neurons. Here's to hoping this research helps is discover why we evolved to sleep.
- pstuart 9y agoIsn't the latest thought that it's to take the brain down for maintenance to flush out debris from processing done during the day? (citation needed)
- ringaroundthetx 9y agoits one thought and it answers nothing
- pstuart 9y agohttp://www.npr.org/sections/health-shots/2013/10/18/236211811/brains-sweep-themselves-clean-of-toxins-during-sleep http://www.npr.org/sections/health-shots/2013/10/18/23621181...
- amelius 9y agoBut why didn't our brain evolve to take the debris out while it s working?
- pstuart 9y agoUnqualified anonymous internet answer: it's probably too busy. I believe the brain actually shrinks slightly and channels expand to aid in the flushing. Anectdata: note how when you're really tired you can't think clearly? Also, how (apparently) if one goes without sleep for too long then the brain suffers irreparable damage.
- deleted 9y ago[deleted]
- Khanthulhu 9y agoBut what if we evolved sleep before we evolved brains? Might it then have a different benefit and the brain ones came later?
- pbhjpbhj 9y agoThe nervous system is mentioned in the OP: >Cassiopea has no brain to speak of — just a diffuse “net” of nerve cells distributed across their small, squishy bodies. These jellyfish barely even behave like animals. Instead of mouths, they suck in food through pores in their tentacles. They also get energy via a symbiotic relationship with tiny photosynthetic organisms that live inside their cells. // From a very cursory glance I can't see how they're differentiating low energy level from lack of "sleep" when they're keeping the jellies "awake". Can that behaviour (resting more the next day) just be explained by low energy reserves, and the jellies needing more time to glean energy from the photosynthesising organisms/cells? Don't plants in winter "sleep" according to their definition; they can wake with a "false spring".
- tzs 9y agoModerators: the title should be changed to the actual article title, which is: "Scientists just discovered the first brainless animal that sleeps" The submitted title, "Scientists just discovered the first animal without a brain that sleeps", is ambiguous. In addition to the correct meaning, it could also have meant the first animal whoe brain does not sleep.
- GuiA 9y agoAre there animals who sleep but whose brains don’t sleep? Are there animals who don’t sleep but whose brains sleep? While ambiguous from a purely grammatical point of view, it does not seem ambiguous from a “common sense” point of view.
- wavefunction 9y agoIt seems that a variety of animals exhibit at least phases of sleep where one hemisphere or part of a brain is asleep while the other is awake: https://en.wikipedia.org/wiki/Unihemispheric_slow-wave_sleep https://en.wikipedia.org/wiki/Unihemispheric_slow-wave_sleep
- tzs 9y ago1. It is not known whether or not pelagic fish sleep. They do not show any of the external signs that are used to infer sleep in other species. Many scientists believe that to solidify and organize memory and learning the brain needs a period with little or no environmental distractions, and that the purpose of sleep is to provide such a period. Pelagic fish live in an environment with such a sparse environment that their brains may be able to do that processing without disconnecting and so do not need to sleep. This means it is plausible that there are animals with brains whose brains do not sleep. If such an animal is shown to exist, it will be the first such case, and so a headline saying that the first animal with a brain where the brain does not sleep is a plausible headline. 2. There are a variety of externally observable behaviors of animals that indicate that the sleeping (especially when "externally observable" includes "observable when hooked up to a variety of instruments"). Not all of these are associated with functions that require a brain. Hence, it is plausible that there is a brainless animal that exhibits some of these sleep-associated behaviors, perhaps even enough of them that it would make sense to say they sleep, even though they have no brain. Hence, a headline saying the first animal that does not have a brain yet sleeps has been found is plausible. If we have to decide that one of these interpretations is the one people would expect by "common sense", I would argue that it is the first one. Yes, I realize that most people will not know about our uncertainty over the sleep or lack of sleep in pelagic fish, so would not come to the first interpretation by that route. However, most people's experience with sleep is based on their first hand knowledge from doing it themselves almost every day, and from talking to other people who do it, and from observing it in fairly intelligent animals such as dogs and cats. They are going to think of sleep as a cognitive thing, something that only animals with brains can do. Since they will have dismissed sleep without a brain as not even possible, they would go for the other interpretation--a brain that does not sleep. So even if we conclude that the submitted title really only has one "common sense" reading, that reading is the wrong one, so the headline is still a bad headline and should be changed.
- yourkin 9y agoNot an expert on jellyfish physiology, but might there be a distinction between "a sleep-like state" and being plain "tired"? After doing some physical activity animals tend to need some rest. Exhaustion is much less of an exciting phenomenon than sleep is.
- jldugger 9y agoIf it were simply physical exhaustion, you'd expect to see some sleeping during the day, or be able to induce exhaustion.
- yourkin 9y agoInduced exhaustion is one way to test it, yes. Can't say from the article if they ruled it out. Correlation of the rest pattern with a day-night cycle does not necessarily imply that the "sleep-like" state is indeed sleep, and not just a power-down low-metabolical wait-state used for the bio-chemistry to catch up after a day of activity is over.
- cetalingua 9y agoSleep is typically defined by the brain waves activities, delta waves, theta waves, etc., each corresponding to a specific sleep stage. These are physiological markers of sleep. There are also states of "quiet wakefulness" that share behavioral characteristics of sleep, like immobility, for example, but are not sleep per se. Many "simple animals" like a fly, or a caterpillar or a bee have periods of inactivity that could be an example of rest. But sleep and rest are not the same. If we put brain waves aside, we are left with the behavioral definition of sleep: it is a state of reduced awareness of the surroundings, there will be some latency in arousal, it is reversable, and it is associated either with immobility or at least reduced activity. This study obviously used this definition, so it is not exactly being "tired".
- yourkin 9y agoThank you for articulating the difference between the two. Can it not be the case with exhaustion also, that awareness and/or reaction times are reduced? Cognition certainly is affected after strain in higher order animals and muscle cells need to replenish ATP. Removing brain waves from the equation, it seems like the whole question of what attests for sleep gets blurry.
- ehutch79 9y agospoiler: it's merely the avatar of a 4th dimensional eldritch horror and is actually studying the scientists before treating our realm as a cheap buffet.
- nub3 9y agoIn my humble opinion every animal consistent of multiple cells alive on this planet developed sleep for just one reason: the very same reason plants sleep. Our planet has a night phase and without sun little energy is left. So as a consequence the best one can do is to clean up internal processes or go into some sort of energy saving mode. Ofc this is heretic to some individuals... But Ockham's razor tells me I'm right.
- ColanR 9y ago> But Ockham's razor tells me I'm right. _probably_ right. Wikipedia: "Since one can always burden failing explanations with ad hoc hypotheses to prevent them from being falsified, simpler theories are preferable to more complex ones because they are more testable." [1] [1] https://en.wikipedia.org/wiki/Occam%27s_razor https://en.wikipedia.org/wiki/Occam%27s_razor
- fcbrooklyn 9y agoAnd this is easily testable. We just house a population of animals who sleep in a hermetically sealed environment that provides all that they need, but is never in darkness. After a couple of hundred million years we open the door and see if anyone is napping.
- hnzix 9y agoNot even "probably" right. Eg Quantum Physics is more complex than Newtonian. OcRaz is a heuristic that advises that simpler hypotheses should be tested first. It's not a magic SCIENCE! gun.
- itchyjunk 9y agoMaybe sleep is linked to neurons? I did read a comment about plants sleeping but i haven't researched it yet.
- meri_dian 9y agoSo what this may be telling us is that sleep is required for beings with nerve cells, rather than solely for those with concentrated and clearly defined brains. This would make sense. All animals with brains sleep, but diversity of brain configuration and design exhibited across all of these different animal species would indicate that there's no single aspect of a brain that demands sleep, and therefore sleep is not an emergent property of collections of neurons forming brains but something the neurons themselves demand in order to function.
- jldugger 9y agoPossible. Or it could just be light as a confounding signal -- they get energy from it, after all, and animals with brains and eyes will spend energy more efficiently during the day. A much older article on jellyfish sleep suggests this proposed advantage, at least: https://search.proquest.com/openview/c958b584511e462a64623c59b7a6bd0a/1?pq-origsite=gscholar&cbl=40810 https://search.proquest.com/openview/c958b584511e462a64623c5...
- meri_dian 9y agoWell I was thinking that light could impact the availability of their food source and so what the researchers interpret as sleep is just some other form of energy conservation, but the 'groggy' behavior of the jellyfish in their one experiment made me think that their energy conserving state does involve their neurons and so at that point it's hard to distinguish energy conservation from sleep.
- Obi_Juan_Kenobi 9y agoThe three criteria mentioned are designed specifically to avoid confusion with general metabolic factors like you suggest.
- shpongled 9y agoI think this is a good guess. I'm not a neuroscientist (but I am a biochemist), but I could see a valid hypothesis involving receptor desensitization.
- deleted 9y ago
- ColanR 9y ago> “When you start working on something totally crazy, it's good to get data before you tell anybody,” Abrams said. It's too bad that this seems to be the environment that our up-and-coming generation of scientists operate in.
- deleted 9y ago[deleted]
- cetalingua 9y agoWhat is even more interesting is why exactly do they "sleep" at night? Do they have some sort of circadian rhythm? They are filter feeders, so the time of the day should not be that important, after all they can filter feed at night? Maybe it is a byproduct of being in lab? Since they are fed during the daytime, they might have "adjusted" to the lab schedule? They need light though, for their photosynthesizing symbionts.
- Someone 9y agoThey (http://travelnq.com/australian-box-jellyfish/ http://travelnq.com/australian-box-jellyfish/) or their food (https://www.nature.com/scitable/blog/saltwater-science/what_makes_plankton_migrate https://www.nature.com/scitable/blog/saltwater-science/what_...) might move vertically between day and night, with the jellyfish being unable to follow their food on part of their depth range. For example, jellyfish might get sunburn at low depths. (Aside: that first link, from 2014, already states that box jellyfish sleep, so this doesn’t seem to be as new as this article claims it to be. What (I guesstimate) is new is that they did pharmacological work to show that the jellyfish didn’t simply ‘not move’)
- siproprio 9y agoThey only found out now about teenagers?
- rayalez 9y agoSomewhere I've heard a cool idea that sleep might be the "default" state of the living organisms. Most of the time you want to rest and conserve energy, so sleeping is just how we are, it's waking up to get food and procreate is the "strange" thing we do. No idea if this makes sense scientifically, but it's fun to think about. Or maybe animals that walk around during the time when there's no light just get themselves into trouble more often and end up dying out of the gene pool. Might as well shut down during the dangerous time and use it for repair.
- blubb-fish 9y agoIt's fun to think about but I don't think it makes sense b/c sleep obviously serves (at least for human beings) the awake state.
- tpeo 9y agoThe only issue with this idea is that it really ... doesn't tie in with evolution. Because ultimately, the default state of any organism should be to be attempting to reproduce. But I stress "ultimately", because there's nothing which impels us to think that needs to be the case at all times. Idling can be a successful short-term strategy, even if not in perpetuity.
- peterburkimsher 9y agoThe researchers lost sleep to research sleep. A follow-up question I'd like to see researched is jet lag. Why do the jellyfish sleep during those hours? Can they adjust their circadian rhythm to a different time zone?