You know how people like to say that, after a nuclear apocalypse, cockroaches will be the only survivors? Not likely. Cockroaches are tropical insects and in higher latitudes can live only in artificially warm places, like your basement. Shut the heat down, and they’ll die off. No, the smart money for nuclear survivors is on tardigrades, which are microscopic animals that can handle almost anything you throw at them, and are also very cute.
|Tardigrade. Don't say it's not cute.|
In contrast to most microscopic creatures, which rush around frantically, tardigrades lumber about with a slow, bear-like gait, feeding on the fluids of plant and animal cells. More than 1100 species have been described. They live everywhere anyone has looked, in both salt and fresh water and on land, where they usually inhabit damp vegetation such as moss or lichens. They’ve been found in tropical forests, in the Arctic Ocean, in the Himalayas at altitudes above 20,000 feet, and in the ocean depths below 13,000 feet. And boy, are they cute.
Terrestrial tardigrades are famous for their ability to withstand extreme conditions. Despite dwelling on land, these little critters are actually aquatic, living within a thin film of water maintained by the damp pockets and pools in the moss and lichens they call home. When their habitat dries out, tardigrades are able to enter cryptobiosis, a hibernation-like state in which their metabolic rate is lowered to .01% of normal, the water content of their bodies drops below 1%, and they shrivel to about one-third their regular size. When their environment becomes damp again, they rehydrate and come back to life.
In cryptobiosis, tardigrades can survive temperatures, pressure, and radiation that would be lethal to almost any other animal. They have been found in the Antarctic at -80° Celsius. Under experimental conditions they have survived being cooled to -200° C for 20 months and being heated to +151° C. They can go without food or water for ten years. They’ve been subjected to as much as 570,000 roentgens of ionizing radiation (500 roentgens would kill a person), pressure of 5800 pounds per square inch, and extreme levels of carbon monoxide, carbon dioxide, nitrogen, and sulfur dioxide, and have come out of it smiling. In 2007, they became the first multicellular animal to survive in outer space when researchers from the European Space Agency launched them in a vehicle 260 kilometers above the Earth and opened the window, exposing them to direct solar radiation and vacuum conditions. They came back fine. And just as cute as ever.
That’s why tardigrades get my vote for most likely to survive a nuclear war. What other living creature can go without eating for ten years, endure high levels of toxic substances, and survive in outer space? Okay, Keith Richards. But you can’t call him cute.