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The mysteries of the planarian
February 5, 2014 2:50 PM   Subscribe

Animal Loses Head But Remembers Everything: "What we do know is that memory can be stored outside the brain - presumably in other body cells - so that memories can get imprinted onto the new brain as it regenerates."
posted by paleyellowwithorange (33 comments total) 19 users marked this as a favorite

 
In other words, it's totally reasonable that the ghola Duncan Idaho in the Dune series remembers his past each time he's reanimated. I think that means everything else in the books are plausible science fact as well, yeah?
posted by thedaniel at 2:55 PM on February 5 [21 favorites]


I'd be more amazed if a worm they grew from a single cell remembered that. But this is still pretty amazing.
posted by kafziel at 3:02 PM on February 5


It's been long known that certain French people can store their memories in pastries.
posted by benito.strauss at 3:03 PM on February 5 [32 favorites]


How much planarium do you need to retain the memory? Half? A quarter? Also, the head looks like a little devil's face from South Park.
posted by Joe in Australia at 3:08 PM on February 5


You've got to wonder how this is possible. But it reminds me of an experiment I read about somewhere where researchers taught planarians a behavior (I think it was how to navigate a maze), then blended 'em up and served them to other planarians, and the cannibals subsequently learned to navigate the maze much faster than their predecessors. So the memories must be stored or backed up somewhere that can survive blending and digestion, at least partially.
posted by Kevin Street at 3:09 PM on February 5 [2 favorites]


More proof that Alan Moore's run in Swamp Thing was prophecy
posted by The Whelk at 3:11 PM on February 5 [4 favorites]


Calling Dr. Herbert West, Dr. West to the white courtesy phone!
posted by Big_B at 3:12 PM on February 5 [3 favorites]


It's been long known that certain French people can store their memories in pastries.

Technically, that was just a memory trigger, like slipping on a stone. The memories were stored elsewhere; exactly where is an eternal mystery.
posted by GenjiandProust at 3:24 PM on February 5


Kevin Street: "But it reminds me of an experiment I read about somewhere where researchers taught planarians a behavior, then blended 'em up and served them to other planarians, and the cannibals subsequently learned to navigate the maze much faster than their predecessors."

I'm pretty sure that's how the training dept and the commissary function here at my workplace.
posted by Hairy Lobster at 3:44 PM on February 5 [11 favorites]


You've got to wonder how this is possible. But it reminds me of an experiment I read about somewhere where researchers taught planarians a behavior (I think it was how to navigate a maze), then blended 'em up and served them to other planarians, and the cannibals subsequently learned to navigate the maze much faster than their predecessors. So the memories must be stored or backed up somewhere that can survive blending and digestion, at least partially.

The experiment you're talking about was either a fluke or just a bias, the effects couldn't be reproduced.
posted by kafziel at 4:23 PM on February 5 [9 favorites]


Perhaps the planarians secrete a chemical marker after eating that indicates "good food found here". It probably smells like planarian farts.
posted by b1tr0t at 4:53 PM on February 5 [1 favorite]


Given how different this critter is from you and me, I have to wonder if there was any reason to believe that its "head" was the locus of its memory in the first place. Is there anything resembling a central nervous system the planarian "head"?
posted by baf at 4:59 PM on February 5 [2 favorites]


The experiment you're talking about was either a fluke or just a bias,

I was going to be all "I saw what you did there," but then I did a little research and found that, while planarians and flukes are related, it is a weird and complex relationship. Way to step on my joke, you legless regenerating killjoys!
posted by GenjiandProust at 5:03 PM on February 5 [14 favorites]


MetaFilter: legless regenerating killjoys.

Am I doing it right?
posted by Woodroar at 5:15 PM on February 5 [6 favorites]


No. You'll need to eat more MeFites if you intend to master that technique.
posted by notyou at 5:32 PM on February 5 [8 favorites]


Intelligence can be eaten: THE BEGINNING WAS THE END
posted by Strange Interlude at 5:47 PM on February 5 [2 favorites]


Thanks, GenjiandProust. I was about to go do the same research about the same joke and then experience the same disappointment.

This is pretty basic sci-fi where they clone or regenerate someone from a couple cells and the result already knows all the stuff the original did like English, object permanence, and the plot so far.
posted by aubilenon at 5:48 PM on February 5 [2 favorites]


No. You'll need to eat more MeFites if you intend to master that technique.

*Hannibal Lecter smirk*
posted by The Whelk at 6:18 PM on February 5 [4 favorites]


These researchers were really pulling this info out of their asses. I don't mean that in a snarky way, that's just where the information was stored in their bodies.
posted by The 10th Regiment of Foot at 6:31 PM on February 5 [3 favorites]


> But it reminds me of an experiment I read about somewhere where researchers taught planarians a behavior (I think it was how to navigate a maze), then blended 'em up and served them to other planarians, and the cannibals subsequently learned to navigate the maze much faster than their predecessors.

If it makes you feel better, the scientist who lead that study later founded Worm Runner's Digest, which became an antecedent of the Annals of Improbable Research.
posted by ardgedee at 7:04 PM on February 5


I think this was all covered back in the early nineties in a fine little documentary called The Borrower.
posted by metagnathous at 9:55 PM on February 5


See, it's all in this one book... THE BIBLE!
posted by mazola at 10:23 PM on February 5


I work in a planarian lab, so I was really excited to see this post!

> Is there anything resembling a central nervous system the planarian "head"?

Despite their simple appearance, planarians actually are quite complex with "brains" and other distinct tissue systems. They do have a central nervous system, consisting of two cephalic ganglia (similar to our brain lobes) at the head and two ventral nerve cords which run down the length of its body (like our spinal cord). They even express a variety of neuron types and neuropeptides: check out these really cool images of the planarian CNS from Collins et al in PLoS Biology!
posted by eikosi at 12:56 AM on February 6 [6 favorites]


According to National Geographic's account, after a short refresher course, these worms-with-new-heads "remembered where the light spot was, that it was safe, and that food could be found there. The worms' memories were just as accurate as those worms who had never lost their heads."

Short refresher course?

So these worms grew new heads with old memories, a remarkable finding, particularly when you consider it took 14 days or so for the head to grow back. How'd the worms do it? Once again, "We have no idea," Michael Levin told National Geographic. Since these animals were briefly brainless after their decapitation, he says, "What we do know is that memory can be stored outside the brain — presumably in other body cells — so that [memories] can get imprinted onto the new brain as it regenerates."

Presuming something is not knowing.

I don't understand the results after the use of the refresher course. The new heads ended up doing as well as the old heads afterwards. But there are so many things here which could lead to a more obvious answer than somatic cells retain memory info. Another way to pose a criticism would be to ask that if they did retain memory elsewhere in the body, why did they need a refresher course? Did they take another worm that learned light=good and not behead him and put him in the exact same conditions of no-head for 14 days and then compare it to new-heads behavior?


Given how different this critter is from you and me, I have to wonder if there was any reason to believe that its "head" was the locus of its memory in the first place. Is there anything resembling a central nervous system the planarian "head"?

True that. Why don't they take a cut off tail end, grow it into a full planarian and see if it has retained that long term memory?
posted by hal_c_on at 4:07 AM on February 6


Short refresher course?

PLN 99: Light Safety (Refresher). It used to be called Light Safety (Remedial), but that was seen as embarassing to new (or new-ish, being regenerates) planarians who already have problems with being dismissed as "lower order invertibrates" and "flats."
posted by GenjiandProust at 5:16 AM on February 6 [1 favorite]


I can't but worry that these animals get their memories back and the memories are all of times they made a fool of themselves. "Oh, God, when I was drunk at that party and made that racist joke, and, oh, Jeez, when I was texting shit talk about a friend and then I accidentally sent it to them, and, ah, man ...."
posted by Bunny Ultramod at 5:48 AM on February 6


You've got to wonder how this is possible. But it reminds me of an experiment I read about somewhere where researchers taught planarians a behavior (I think it was how to navigate a maze), then blended 'em up and served them to other planarians, and the cannibals subsequently learned to navigate the maze much faster than their predecessors. So the memories must be stored or backed up somewhere that can survive blending and digestion, at least partially.

I recall reading someone tried replicating this experiment, using a glass maze. Before testing the second set of planaria (the cannibals), the glass maze was cleaned with an acid solution. When the maze was thoroughly cleaned, the second set of planaria took as long to learn the maze as the first set had — i.e, no 'ingested memory' effect.

The acid wash removed traces left by the planaria which had become stronger as they re-inforced the 'solved maze' path.

I wonder if they cleaned the maze before each run, how long it would have taken any planaria to 'learn' the maze?
posted by rochrobbb at 8:10 AM on February 6 [1 favorite]


ANIMAL WITHOUT BRAIN STORES MEMORIES SOMEWHERE BESIDES THE BRAIN IT DOESN'T HAVE

(You can call the planarian cerebral ganglia a brain, but it's barely bigger than the peripheral ganglia.)
posted by straight at 8:29 AM on February 6 [2 favorites]


So, if a planarian happened to have certain information about an alleged crime and was going to testify in court, is there any possibility that its memory could be erased? I'm just curious.
posted by orme at 9:33 AM on February 6 [1 favorite]


So, if a planarian happened to have certain information about an alleged crime and was going to testify in court, is there any possibility that its memory could be erased?

More importantly, if a planarian knew the location of a bomb, would you be required to cut off its head and feed it to another, friendly planarian? To stop terror? I mean, the first one would grow its head back later, so, no biggie.
posted by GenjiandProust at 10:40 AM on February 6


Although ectoderm and endoderm layers may appear superficially similar, and both consist mostly of the same two types of cells, slender sensory cells and columnar epithelial cells with muscle fibrils in their bases, it has been shown that during development they have undergone a basic differentiation which cannot be reversed merely by changing their position in the hydra. In one experiment about sixty hydras were turned inside out (by manipulation with needles). About a third of the hydras did not adjust but underwent a period of "depression" followed by death. About a third were able to return themselves right side out. And about a third of the hydras remained turned but readjusted themselves by a migration of the cells of the ectoderm and endoderm past each other in opposite directions through the jelly-like material between. In one hydra the cells had migrated and taken up their normal positions within two hours after the hydra had been turned inside out. Such reorganized hydras ingested food two days after the time of turning.
- Ralph Buchsbaum in
Animals Without Backbones
posted by carsonb at 10:59 AM on February 6 [1 favorite]


More importantly, if a planarian knew the location of a bomb, would you be required to cut off its head and feed it to another, friendly planarian? To stop terror? I mean, the first one would grow its head back later, so, no biggie.
Don't forget all the dramatic tension that you get for free with the 14-day period it takes to regrow the head.
posted by b1tr0t at 3:57 PM on February 6 [1 favorite]


Neat.
posted by homunculus at 11:02 PM on February 6


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