Tardigrades, known as moss piglets or water bears, are extremophiles, organisms capable of surviving “the crushing pressure of the ocean floor, the DNA-shredding powers of radiation, temperatures just one degree above absolute zero (the temperature at which molecular motion ceases), and even the vacuum of space.” Dehydration, starvation, and air deprivation can’t kill these remarkable animals. A flexible protein allowing tardigrades to suspend metabolism is key to their survival.
Fun fact: Tardigrades are visible using a common microscope.
Believed to have evolved at least 500 million years ago, tardigrades have survived five mass extinctions that killed off other species, including the dinosaurs. They’re distant relatives of spiders, crabs, and velvet worms.
Females are usually larger and more common than males, and some species can reproduce by parthenogenesis, meaning the females can lay self-fertilized eggs without male sperm.