Tardigrade genome has been sequenced – most foreign DNA of any animal | Hacker News Reader

Tardigrade genome has been sequenced – most foreign DNA of any animal

sciencealert.com

115 pointshenriquemaia17 comments

Key quotes

>Before this, the rotifer – another microscopic water creature – was believed to have the most foreign genes of any animal, with 8 or 9 percent. But the new research has shown that approximately 6,000 of the tardigrade’s genes come from foreign species, which equates to around 17.5 percent.

>The team hasn't investigated exactly how this gene-stealing is happening just yet, but they propose that it's a result of one of the tardigrade's other crazy survival mechanisms – the ability to dry out until its body is less than 3 percent water, and then come bounce back once they're rehydrated.

> When this desiccation happens, scientists know that their DNA breaks down into tiny pieces. They also know that when their cells rehydrate, there's a point in time when the cell nucleus is leaky, allowing DNA and other molecules to pass through. That means that while the tardigrade is quickly patching up its own genome, it may accidentally be stitching in another organism's genes.

Ah, so that's where Cixin Liu got the idea from for Three Body aliens.

That's incredible!

All adult tardigrades of the same species have the exact same number of cells in their bodies [1] – for some reason, I find that extremely fascinating. I wonder how this interacts with the large amount of foreign DNA in their genes.

[1] https://en.wikipedia.org/wiki/Tardigrade#Anatomy_and_morphol...

> The foreign DNA comes primarily from bacteria, but also from plants, fungi, and Archaea.

Or it's the other way around. Maybe singular cell life on Earth were just tardigrade cancer cells that managed to survive outside of their bodies.

Tardigrades arrived via comet and we're the descendants of their cancers?

Maybe[1]. Scientists don't like to waste time on alien life origin theory as it doesn't really solve anything, we still would want to know how tardigrades' home planet created life.

[1] with chance damn close to zero

If there was a competition to find the craziest idea that will one day be found to be true - I'd pick panspermia. Although all life being descended from tardigrade cancer is a little out there even for me.

Worth it just for the water bear gif. Fascinating history.

Unsourced gif appears to be from the series "Cosmos: A Spacetime Odyssey", episode 2, "Some of the Things That Molecules Do". Clip: https://www.youtube.com/watch?v=2I-PQxuPkjA

I believe it's a mock-up from NDT's Cosmos.

That’s CG, not a microscope.

Here's a short documentary shot with microscopes: https://www.youtube.com/watch?v=o9kPQ0GY_W8

This is beautiful

Look at it go, weee!

My kid loves the PBS show "cat in a hat". There is an episode about the Tardigrade (#207):

> Synopsis: Nick and Sally are trying to guess what animal is the toughest one — is it a lion? Oh no, it must be the enormous elephant! Why not at all, says The Cat. The toughest of all is a teeny tiny Waterbear. Huh?

> Educational Objective: How TARDIGRADES (also known as Waterbears) survive extreme heat, cold and even being a trip into space.

Zerg collecting the "essence". Nice.

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