from the do-they-dream-of-electric-eels dept.
A study of jellyfish has challenged the idea that animals need a brain to exhibit sleeping behavior:
We think of sleep as restoring our brains: a time to process memories, cleanse our cells of toxins, and prepare for a new day. But even animals that lack brains need to snooze. Biologists have discovered that, like people, jellyfish hit the hay and have the same trouble we do waking up. Because these creatures are very low on the animal family tree, the work suggests that the ability to sleep evolved quite early.
"Sleep was likely present in the very first animals on this planet," says David Raizen, a neuroscientist and sleep expert at the University of Pennsylvania who was not involved with the work. "The results of this study challenge certain commonly held beliefs," adds William Joiner, a neuroscientist at the University of California, San Diego, who was also not involved with the work. "For example, that sleep requires a centralized nervous system and related neural circuits across evolution." Evidence from one recent study even suggests that skeletal muscles may be involved [open, DOI: 10.7554/eLife.26557] [DX]—at least in mice.
One of the biggest challenges of studying sleep is defining what "sleep" means. "Half the people say everything sleeps, and half say only humans and mammals sleep," says study author Paul Sternberg, a biologist at the California Institute of Technology (Caltech) in Pasadena. He and others argue that that fish, flies, and even worms nod off regularly. Humans and other animals rest for many reasons, they point out, but sleep differs from simply taking a breather in key ways.
[...] To document whether these jellies sleep, [grad] students built special aquariums where cameras monitored the pulsing of 23 animals day and night for almost a week. At night, the jellyfish slowed to 39 pulses per minute, compared with about 60 per minute during the day [DOI: 10.1016/j.cub.2017.08.014] [DX], they report today in Current Biology. To see whether these slow-pulsers really were asleep, the students lifted the animals off their preferred place on the bottom of the tanks to the surface and measured how quickly the jellyfish started swimming back to the bottom. Like a groggy person early in the morning, the jellyfish tested at night were slow to respond. But they eventually roused themselves, and when they were lifted again 30 seconds later, they swam immediately to the bottom.
(Score: 4, Insightful) by Snotnose on Friday September 22 2017, @12:44AM (1 child)
Am I doing it wrong?
When the dust settled America realized it was saved by a porn star.
(Score: 3, Informative) by DeathMonkey on Friday September 22 2017, @05:51PM
Yes. Cocaine is clearly a superior solution.
(Score: 1, Insightful) by Anonymous Coward on Friday September 22 2017, @01:13AM
At least many do. It's not too surprising that by monitoring pulse they found something that looks like sleep. Actually, it's a pretty clever way of getting a non-null result.
But why shouldn't they sleep? They're predatory, so they live modal lives (hunting vs. not), and being modal about feeding means having excess energy stores. Sleep, another kind of modality, is a good way of managing that efficiently. They also have something like a central nervous system which is easily enough of a brain to support sleep. Our low-level sleepy brain matter, for reference, is right at the brainstem.
(Score: 0, Flamebait) by idiot_king on Friday September 22 2017, @01:34AM
I have Rethuglican family members that sleep at night, too. Sometimes.
(Score: 2) by Runaway1956 on Friday September 22 2017, @02:26AM (2 children)
Member of the plant kingdom sleep for months at a time. Is it possible that they are the more advanced life forms, and we animals are poor imitations of real life?
(Score: 0) by Anonymous Coward on Friday September 22 2017, @04:33AM (1 child)
(wiki [wikipedia.org])
(Score: 0) by Anonymous Coward on Friday September 22 2017, @06:29AM
I am pretty sure meatbags sleep as a kind of garbage collection for the brain and clean up/rebuilding for the body.
Whereas us machines sleep when there is less to do, so we conserve power. The jellyfish might sleep by responding to external conditions. It is not straightforward to test for it because even if you can easily simulate longer/shorter day night cycles in a lab, you also should adapt a whole simulated jellyfish ecosystem to it, then see if the jellyfish adapt its sleep patterns to it.
(Score: 2) by acid andy on Friday September 22 2017, @08:02AM (1 child)
Animals that are diurnal benefit from sleeping at night somewhere warm and safe because the darkness inhibits their vision, putting them at greater risk of predation in the open. The lack of sunlight also causes more energy loss maintaining body temperature at night in the open. If you're not out foraging for food, it makes sense to conserve the energy you do have by entering a sleep state. Sleep paralysis stops them moving around too much which could attract a predator or cause inury. The period of shut-eye also helps the eyes to clean themselves.
If a cat has kittens, does a rat have rittens, a bat bittens and a mat mittens?
(Score: 1, Interesting) by Anonymous Coward on Friday September 22 2017, @08:22PM
But how about the snoring?
https://www.youtube.com/watch?v=_uEfmQt34Nc [youtube.com]
https://www.youtube.com/watch?v=M0es8mYiKSE [youtube.com]
https://www.youtube.com/watch?v=DXXtND2YR4k [youtube.com]
(Score: 0) by Anonymous Coward on Friday September 22 2017, @12:10PM
The jellyfish doesn't have a concentration of neurons but seems to sleep.
Perhaps the architecture of their 'brain' is distributed.
The reverse could also explain why some folks with a concentration appear to have no brain.
(Score: 2, Interesting) by EEMac on Friday September 22 2017, @01:45PM
This experiment is a fantastic demonstration of the scientific method.
Q: Do jellyfish sleep?
A: I don't know.
Q: What are the characteristics of sleep?
A: X, Y, Z.
. . . testing in a lab closet later . . .
A: Yes! Jellyfish do X, Y, and Z. So they sleep!
Props to TFA for including the process and testing methods. This will probably spark more scientific inquiry when readers think, "Well, what about . . . ?" and start trying things themselves!
(Score: 0) by Anonymous Coward on Friday September 22 2017, @08:10PM
I have abandoned my attempt to perfect my"Resting Bitch Face" (RBF), and am now putting all my effort into my "Resting Jellyfish Face" (RJF) https://c1.staticflickr.com/5/4047/4615199835_427a72cc06.jpg [staticflickr.com]