Scientists discover the first brainless animal that sleeps
washingtonpost.com
washingtonpost.com
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.
A much older article on jellyfish sleep suggests this proposed advantage, at least: https://search.proquest.com/openview/c958b584511e462a64623c5...
But I thought that was the obvious part? Brains are made of neurons and (I thought) neurons produce biproducts that have to be "cleaned up" or they slow down/stop working. Isn't that also why (or one possible reason they think why) people with Alzheimer lose their brains? That it was somehow related to the brain's neuron "clean up" helpers that stop working or die off.
Then again, the less obvious thing is that the spinal cord has neurons. So I wonder if this comes into play there...
Here's to hoping this research helps is discover why we evolved to sleep.
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.
>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".
(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’)
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".
Removing brain waves from the equation, it seems like the whole question of what attests for sleep gets blurry.
Now, with "lower" animals it gets tricky, because all we have is a behavioral definition of sleep. But still, it makes a distinction of reduced awareness, arousal latency. Can we call it "sleep" in these animals, jellies included? Maybe not, maybe it is some sort of proto-sleep state?
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?
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]
You're quite right to note it's heuristic nature, some people use it as if it's truth generating.
This doesn't explain the huge number of nocturnal animals that sleep during the day and are active at night.
Seriously though, the existence of nocturnal animals kinda puts that argument to bed. While there might be selection pressure to specialise within day or night cycles, it's simply not plausible that no animal, in the vastness of the biospehere, has not generalised to do both, without some critical and fundamental flaw.
Point in case, bats as my primary example seem to be pretty archaic, with highly developed specializations, but nothing really highly developed. Which I see as an expression of the low entropy in the dark (the signal to noise ratio for sound is rather good at night though). Deep see animals are mostly outliers inhabiting a niche, as well. Whereas people as the highest developed species, if I may say so myself, don't even quite get along with crossing the day-night boundaries, I don't see your argument at all. You are rather proving the point.
Predators which hunt at night occured later (another heretic thought).
I'm curious why you keep presenting your opinions as extreme outliers when they aren't particularly outside mainstream scientific thought?
It's too bad that this seems to be the environment that our up-and-coming generation of scientists operate in.
"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.
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.
https://en.wikipedia.org/wiki/Unihemispheric_slow-wave_sleep
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.
Very interesting topic.