Natures wonders: how tardigrades survive (Introduction)

by David Turell , Thursday, July 27, 2017, 22:09 (2674 days ago) @ David Turell

More research show that tardigrades replace missing water with protein to hold shapes:

https://www.newscientist.com/article/2142047-tardigrade-genomes-help-explain-how-they-s...

"For most animals, dehydration spells disaster. The membranes inside their cells collapse without water to hold them in place, causing the cells die. But for two species of tardigrade whose genomes were examined in the new study – Hypsibius dujardini and Ramazzottius varieornatus – a lack of water isn’t fatal.

"A team including Mark Blaxter at the University of Edinburgh, UK, and Kazuharu Arakawa at Keio University in Tokyo has confirmed that the two species make highly soluble, tardigrade-specific proteins. These help the insides of cells maintain their shape even in the absence of water and so avoid damage. But one of the two tardigrades needs a heads-up.

“'The strategies are the same, but H. dujardini needs 24 hours’ warning to make these proteins, and R. varieornatus is ready at all times,” says Blaxter.

"This difference relates to how fast they can dry out. R. varieornatus is often found in moss on concrete roads and can dry out within 30 minutes, while H. dujardini lives in ponds and takes 24 to 48 hours to dry. But the genome studies show that the two share an almost identical set of genes that kick in when water vanishes, says Arakawa. The only difference is how those genes are regulated, he says.

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"The findings indicate that tardigrades are more closely related to nematodes, despite their outward arthropod-like appearance. This comes from looking at the Hox genes in tardigrades and some of their invertebrate animal relatives. These genes are responsible for the position and alignment of body limbs in animals. Tardigrades are missing five of the genes – and nematodes lack exactly the same ones."

Comment: Life has some strange branches.

But there are still other tardigrade secrets to fully unravel. In their dried up state, they can remain dormant for years – withstanding freezing temperatures, radiation and even being sent into space.