Tardigrades water bears

[Huskisson]

Hi
I have a student who wants to dehydrate and rehydrate tardigrades. We have ordered them have been able to find them easily under the microscope and then leave them overnight on the slide to dehydrate but they all die and will not come back to life. What are we doing wrong? We have tried spring, purified and distiller water. Any help or advice would be appreciated.

[SciB]

I don't know why your water bears died when you let the water evaporate. They are certainly known for their ability to withstand desiccation, extreme cold and even the vacuum of space.

I read the wiki on tardigrades (https://en.wikipedia.org/wiki/Tardigrade) which is the family name of water bears and it says that: "Several species of tardigrade regularly survive in a dehydrated state for nearly 10 years. Depending on the environment, they may enter this state via anhydrobiosis, cryobiosis, osmobiosis, or anoxybiosis. While in this state, their metabolism lowers to less than 0.01% of normal and their water content can drop to 1% of normal.[8] Their ability to remain desiccated for such a long period is largely dependent on the high levels of the nonreducing sugar trehalose, which protects their membranes. In this cryptobiotic state, the tardigrade is known as a tun.[31]"

There are over 1000 species of water bear and I don't know if they are all equally able to withstand drying. Also, the way they enter the dried state may be important. There's a term for this state that I did not know and it is 'cryptobiosis' (https://en.wikipedia.org/wiki/Cryptobio ... ydrobiosis). It means that all metabolic activity has stopped and the organism has gone into suspended animation until conditions improve. When cryptobiosis is achieved by drying, it is called anhydrobiosis.

I did a Google search for how to put water bears into a cryptobiotic (anhydrobiotic) state. There is a lot of information and you may have to just sift through it until you find a description of how to dry them out. I found one paper that cited a reference in which a cryptobiotic state was induced in one species of water bear, but only 84 out of 139 animals survived. If you only tested a few water bears, you may have had the bad luck to get ones that were unable to achieve cryptobiosis for some reason. According to the paper, smaller, younger animals are better able to withstand drying than larger, older ones. https://www.google.com/url?sa=t&rct=j&q ... 6085,d.dmo

The American Museum of Natural History has an exhibit on tardigrades with great pictures: http://www.amnh.org/explore/news-blogs/ ... ardigrades

I found a long chapter about tardigrades that has a lot of information but is quite technical: https://www.google.com/url?sa=t&rct=j&q ... mo&cad=rja

One thing I discovered in quickly reading parts of the above chapter was that the water bears need to synthesize some sugars to protect their bodies from drying, and this takes a little time. They didn't say how long. It probably varies with the species. Maybe your water bears dried out too fast and weren't ready to go into the anydrobiotic state before all their water was gone. Maybe you could cover the slide so that the water evaporates more slowly.

Do you know what species of tardigrade you have? Did you take a picture of it? Photos would be really helpful. If you have a low power microscope you can take a picture through the eyepiece with a phone camera or any digital camera then compare it to pictures on Google.

Try again with more water bears and let them dry out more slowly so they have time to adapt. This is a really interesting project so please keep posting to let us know what happens!

Sybee