Tardigrades turn into glass when they dry out | Hacker News Reader

Tardigrades turn into glass when they dry out

sciencealert.com

194 pointsDiabloD337 comments

For those needing to look up what Tardigrades are:

From Wikipedia: https://en.wikipedia.org/wiki/Tardigrade

> Tardigrades are notable for being perhaps the most durable of known organisms; they are able to survive extreme conditions that would be rapidly fatal to nearly all other known life forms. They can withstand temperature ranges from −272.222 °C (−458.000 °F) to 149 °C (300 °F),[7] pressures about six times greater than those found in the deepest ocean trenches, ionizing radiation at doses hundreds of times higher than the lethal dose for a human, and the vacuum of outer space.[8] They can go without food or water for more than 10 years, drying out to the point where they are 3% or less water, only to rehydrate, forage, and reproduce.

It's frustrating that Wikipedia editors ignore sig figs. [7] is a wired.com source which quotes 458F (3 sig figs) and thus should be converted to 272C. The quoted 300F is even more suspect, since it's a nicely rounded number.

Considering that -272 C is very close to absolute zero, it makes perfect sense. For example, 0.1 K and 0.5 K are both written as -273 C, but the latter is five times as hot as the former. For best consistency, we ought to use logarithmic Kelvins.

I don't really disagree, but that would make for a rather perverse unit, given that inverse temperatures are already on a logarithm scale relative to the probabilities of microscopic states.

Logarithms are like violence—if it's not flat yet, you need to use more.

Why don't you edit it?

Probably because somebody would just come through and revert it 5 minutes later anyway.

[Citation needed]

I can't tell if this is a joke to prove my point, or if you're serious, but I don't need a reference because I've had multiple personal experiences of this happening. At this point I don't bother any more, it's not really my problem if Wikipedia is inaccurate.

It is fortunate these things are so small, if they were the size of a small dog they would scare the crap out of me. An unkillable eating machine.

They'd make a great Dr Who enemy

Without spine they won't be able to function at that size. Gravitation is mean bitch - weight grows as x^3, but muscular power only as x^2. Mammals are probably the best you can do in "very large" form factor.

Indeed, even at their present size they are called "slow steppers".

On the other hand, actual biology: https://en.wikipedia.org/wiki/Coconut_crab (and re: the "mammals" comment: https://en.wikipedia.org/wiki/Argentinosaurus)

"Video of the most likely way Argentinosaurus walked" -> Very carefully.

No worse than a lobster.

So why/how does an animal evolve to survive hard vacuum and lethal ionizing radiation when you can't experience those conditions here (on Earth)?

This is an argument for panspermia according to Neil deGrasse Tyson. (Real Time with Bill Maher, S13E29)

I was going to say the same thing. Such a hardy species I would think would be the product of an incredible amount of evolutionary progress. How do they fit in with the rest of the living species taxonomy?

Don't get too excited - the Wikipedia article (very good) explores their genome and taxonomy. Fossilised records hard to come by but cambrian and Cretaceous records have been found. So probably boringly terrestrial

Or it could simply mean that they came to Earth a long time ago.

Sure, but as of now, there is no positive indication they are extraterrestrial. They fit into the species cladogram, they don't seem to suddenly appear as a time anomaly, they just seem like extremely tough little guys.

I read somewhere that they can absorb DNA from foreign sources (other animals, etc) into their cells when they rehydrate, leading to an accelerated rate of evolution.

Here's an article about that: http://phys.org/news/2015-11-huge-chunk-tardigrade-genome-fo...

Doesn't really solve the problem of how life first arose. It just pushed the whole thing back into space.

But pushing it into space does open up some interesting possibilities. There must be some very exotic chemistry during and after a supernova, or when a comet has an unusually close encounter with a star.

Being able to survive unearthly conditions may just be a side effect of being able to survive extreme, yet common conditions, such as dehydration.

Also, note that they don't thrive in these conditions, they're merely able to survive for a relatively long time.

Basically dehydration and radiation have the same effect on DNA and other large molecules. The major effect of a hard vacuum is dehydrations. Being able to survive both of these is just a side effect of being able survive dehydration.

I remember reading a"theory" that they might have been alien. Arrived on a meteor or something like that. Would make a cool animated movie with characters.

They thrive in water, but adapted to be able to withstand dry periods by desiccating and stopping their metabolism (you could say their life is suspended, really) and resuming when water returns. In their dry state (anhydrobiosis/cryptobiosis) there's not really anything that would violently evaporate in a vacuum and thus destroy cell structure, like there is in live cells, and they repair DNA damage after they rehydrate, so they're not harmed much by vacuum or ionizing radiation.

> capable of surviving ... prolonged desiccation and near-100 percent water loss

Aren't they the same thing?

One is prolonged, the other is intense.

So, any chance of this particular kind of auto-vitrification could work as a preservation method for human cells, alternative to cryopreservation or plastination?

Url changed from http://www.hexapolis.com/2015/12/23/new-research-shows-that-..., which points to this.

The title reads like a Radio Yerevan joke: they don't "turn into", they are "covered in", and it's not glass, it's protein.

One does not always have to take titles so literally. I expect there to be a bit of "sizzle" not "steak" in a title because it has to catch your eye and compete with other titles.

I had a chuckle yesterday because there was an HN News story that was briefly on the front page with a title something like "95 year old smashes world 200m record". About 80% of the posts complained that the title was misleading because it was the world record for his age group. I would have thought that was self evident - did they really expect a 95 year old to break the open WR for 200m?

It's not glass, but it may be a glass. https://en.m.wikipedia.org/wiki/Glass:

"Scientifically, the term "glass" is often defined in a broader sense, encompassing every solid that possesses a non-crystalline (that is, amorphous) structure at the atomic scale and that exhibits a glass transition when heated towards the liquid state."

Polystyrene is a glass, for example (https://en.m.wikipedia.org/wiki/Glass_transition)

Tardigrades rule!

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