They call them tardigrades, aka “water bears.” They are 0.2 to 1.5 mm in length. they live literally everywhere and there are all kinds of different ones (notice the variation in the number of claws on the “feet”). They are not related to anything; they have their own biological phylum. I think they look like Mini-Manatees. That’s what they should call them. They can survive anywhere, including space.