Americans call tardigrades ‘water bears’ and Europeans call them ‘moss piglets’. I think Africans should call them micro-hippos. They’re obviously more closely related to hippopotamuses than bears or pigs. Just look at them. Anyone can see that’s a microscopic hippo wearing his old wrinkled khaki safari outfit.*
Anyway, they live in water, like bears and pigs don’t. Microscopic, blobby-bodied tardigrades measure mostly between 0.3 to 0.5 millimeters in length. The tiny creatures have endearing features if you have a good enough microscope: fat, lumpy bodies; oblong heads, sometimes with a tubular mouth; four pairs of chubby legs tipped with grasping claws like a sloth. The word tardigrada is Latin for ‘slow stepper’.
They are famed for their ability to survive in extreme conditions, even appearing to come back from the dead. They’re found around the world on damp moss and algae, but you can’t really see them with the naked eye. Yet somehow German dominee-zoologist Johann August Ephraim Goeze discovered them back in 1773. I love it. Back in the days when dominees were useful! I hope he mentioned them in his next sermon on fortitude.
Researchers have found that tardigrades can withstand searing heat up to 149 degrees Celsius and freezing cold as low as minus 200 degrees Celsius. They emerge unscathed after exposure to boiling, high pressure, and the radiation and vacuum of space. They expel the water from their bodies and enter a suspended state. In this state they’re called ‘tuns’. They retract their limbs and shrink into tiny, desiccated balls, emerging only when life-threatening conditions have passed. OK, so that’s not like hippos, but nor is it like piglets. Bears do their hibernation thing, true.
They come in various kinds. Here’s another one and a cute micro-hippo embryo:
Scientists are studying how these amazing beasts do what they do. One is Thomas C. Boothby of the University of North Carolina. He grew up in Africa, so I hope he calls them micro-hippos!
*Matt Simon on wired.com called them something like “cannons in wrinkled khaki”
dominee – preacher, pastor, pontificator