Author Topic: Tardigrades - why can they survive in outer space?  (Read 234 times)

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Online One Above All

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Tardigrades - why can they survive in outer space?
« on: July 29, 2017, 04:55:52 PM »
This is something that's bothered me for a while. These little fuckers can apparently survive in the vacuum of space, even when exposed to solar winds. But how did they develop this ability in the first place? There's no reason why such a defense would propagate through their species, given that solar winds don't impact the Earth's surface. So, why should tardigrades - or any Earth species, in fact - have the ability to survive in an environment that's so different from Earth's, it's literally outer space? Any guesses?
« Last Edit: July 29, 2017, 05:02:03 PM by One Above All »
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Offline Azdgari

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Re: Tardigrades - why can they survive in outer space?
« Reply #1 on: July 29, 2017, 05:02:54 PM »
1. Ask "how" they manage to survive space.
2. Consider how that mechanism might have come about.
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Online One Above All

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Re: Tardigrades - why can they survive in outer space?
« Reply #2 on: July 29, 2017, 05:04:25 PM »
1. Ask "how" they manage to survive space.
2. Consider how that mechanism might have come about.

The only way I see this happening, according to what we know of the development and propagation of beneficial mutations, is that they're not native to Earth, which seems absurd to me.
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Offline Azdgari

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Re: Tardigrades - why can they survive in outer space?
« Reply #3 on: July 29, 2017, 05:05:45 PM »
By what mechanism does a tardigrade physically survive in a vacuum?
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Online One Above All

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Re: Tardigrades - why can they survive in outer space?
« Reply #4 on: July 29, 2017, 05:08:16 PM »
By what mechanism does a tardigrade physically survive in a vacuum?

If memory serves, they enter a sort of stasis, purging themselves of water and just staying dormant. This doesn't answer their remarkable resistance to solar radiation, though, which is something no species on Earth should be adapted to - even if they're shielded from less powerful forms of radiation.
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Offline shnozzola

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Re: Tardigrades - why can they survive in outer space?
« Reply #5 on: July 29, 2017, 05:18:00 PM »
https://www.newscientist.com/article/dn14690-water-bears-are-first-animal-to-survive-space-vacuum/

Quote
The vacuum itself seemed to have little effect on the creatures. But ultraviolet radiation, which can damage cellular material and DNA, did take its toll.
........
In one of the two species tested, 68% of specimens that were shielded from higher-energy radiation from the Sun were revived within 30 minutes of being rehydrated. Many of these tardigrades went on to lay eggs that successfully hatched.
But only a handful of animals survived full exposure to the Sun’s UV light, which is more than 1000 times stronger in space than on the Earth’s surface.

https://www.reddit.com/r/askscience/comments/3r40ro/how_is_it_physically_possible_for_tardigrades_to/
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Re: Tardigrades - why can they survive in outer space?
« Reply #6 on: July 29, 2017, 05:19:42 PM »
https://www.newscientist.com/article/dn14690-water-bears-are-first-animal-to-survive-space-vacuum/

Quote
The vacuum itself seemed to have little effect on the creatures. But ultraviolet radiation, which can damage cellular material and DNA, did take its toll.
........
In one of the two species tested, 68% of specimens that were shielded from higher-energy radiation from the Sun were revived within 30 minutes of being rehydrated. Many of these tardigrades went on to lay eggs that successfully hatched.
But only a handful of animals survived full exposure to the Sun’s UV light, which is more than 1000 times stronger in space than on the Earth’s surface.

https://www.reddit.com/r/askscience/comments/3r40ro/how_is_it_physically_possible_for_tardigrades_to/

Seems I was mistaken. I could've sworn more of them had survived - enough to make a statistical inference that it was a common defense among their species.
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Offline shnozzola

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Offline shnozzola

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Re: Tardigrades - why can they survive in outer space?
« Reply #9 on: July 29, 2017, 05:27:13 PM »
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Offline Azdgari

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Re: Tardigrades - why can they survive in outer space?
« Reply #10 on: July 29, 2017, 07:15:09 PM »
Their dessication abilities would be the key to surviving both the vacuum and the radiation, the latter less directly.  Tardigrades can be dried out almost completely without dying.  One of the main reasons why a vacuum is so dangerous is that it lowers the boiling point of water enough that body temperature is above boiling.  Hell, even room temperature is.  So being able to lose the water from one's body really helps one to survive a vacuum.

The radiation resistance can be explained, at least in part, by the tardigrade's more relaxed relationship with its own DNA.  When a dessicated tardigrade re-hydrates, it takes on the DNA of other organisms into its cells.  A lot.  And it survives this, just fine.  So it's likely that the same amount of radiation damage that would kill the cell of another organism would be par for the course for a tardigrade...to a point.

So, the tardigrade's resistance to the environment of space is a side-effect of its survival mechanisms that it evolved for life on Earth.
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Re: Tardigrades - why can they survive in outer space?
« Reply #11 on: July 30, 2017, 03:42:03 AM »
The radiation resistance can be explained, at least in part, by the tardigrade's more relaxed relationship with its own DNA. When a dessicated tardigrade re-hydrates, it takes on the DNA of other organisms into its cells. A lot. And it survives this, just fine. So it's likely that the same amount of radiation damage that would kill the cell of another organism would be par for the course for a tardigrade...to a point.

So, the tardigrade's resistance to the environment of space is a side-effect of its survival mechanisms that it evolved for life on Earth.

I can accept the way they survive hard vacuum, but not the way they survive radiation. There's a big difference between "let's incorporate this (mostly) intact foreign DNA into our own" and "this DNA has been shredded by radiation to the point it's unrecognizable, but it'll work anyway".
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Online jaimehlers

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Re: Tardigrades - why can they survive in outer space?
« Reply #12 on: July 30, 2017, 06:48:37 AM »
Much of radiation damage to DNA is actually caused by water-based radicals (radiation hits water molecules, and the resulting radicals actually do the damage).  So lack of water would pretty much eliminate that.  And while DNA can be affected directly by radiation as well, it's much easier to hit water inside a cell (normally) than it is to hit the DNA inside the cell.

Lack of water in a dessicated tardigrade probably makes it easier for ionizing radiation to hit the DNA or other critical cell mechanisms, but probably not all that much easier.  And that's probably gonna be outweighed by the reduced likelihood of oxydation due to the aforementioned lack of water molecules to hit.

http://www.rerf.jp/radefx/basickno_e/radcell.htm
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Re: Tardigrades - why can they survive in outer space?
« Reply #13 on: August 01, 2017, 12:52:49 PM »
Much of radiation damage to DNA is actually caused by water-based radicals (radiation hits water molecules, and the resulting radicals actually do the damage). So lack of water would pretty much eliminate that. And while DNA can be affected directly by radiation as well, it's much easier to hit water inside a cell (normally) than it is to hit the DNA inside the cell.

Lack of water in a dessicated tardigrade probably makes it easier for ionizing radiation to hit the DNA or other critical cell mechanisms, but probably not all that much easier. And that's probably gonna be outweighed by the reduced likelihood of oxydation due to the aforementioned lack of water molecules to hit.

http://www.rerf.jp/radefx/basickno_e/radcell.htm

So these little bastards actually did just win the genetic lottery? Wow.
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Re: Tardigrades - why can they survive in outer space?
« Reply #14 on: August 01, 2017, 01:34:08 PM »
It sure seems that way, yeah.  I couldn't help but be curious about it since you were making a good point - traits like that seldom appear in the absence of environmental cues.  But apparently, they really were just that lucky.
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Offline lpetrich

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Re: Tardigrades - why can they survive in outer space?
« Reply #15 on: August 02, 2017, 02:27:42 PM »
A similar case is Deinococcus radiodurans - Wikipedia -- this bacterium can survive 1000 times our lethal dose of ionizing radiation, an amount that is enough to kill a tardigrade. This organism does it by maintaining multiple copies of its genome and rapidly fixing damage to it.

This ability evolved for surviving drying out while still being active -- strains of D. radiodurans that do not survive radiation very well do not survive drying out very well.

I add the qualifier of being active since many organisms can survive dryness by suspended animation, as tardigrades do.

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Re: Tardigrades - why can they survive in outer space?
« Reply #16 on: August 03, 2017, 09:48:02 PM »
It makes me wonder about the evolutionary history of extremophiles in general. I would expect (and could well be wrong) that organisms like radiodurans would have to be under great pressure for their ancestors to be rolling the mutational dice so often that such a string of favorable ones would accumulate.

Or is it simply luck over a more prolonged period? Is there any way to gauge just when a certain genetic change or changes took place in a species' past?
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