 | 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. |
There are about 1,000 different species of tardigrades, some more resilient than others. Tardigrades are found everywhere on Earth, from mountaintops to mud volcanoes, in stone walls and roofs, from tropical rainforests to deserts to the icy Antarctic. They’re common in lichens and mosses (hence the name moss piglet), and feed on plants, bacteria, and smaller invertebrates.
Fun fact: Tardigrades are visible using a common microscope.
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. |  |
Because tardigrades have survived experiments in space, they might provide evidence of extraterrestrial life. The (fringe) theory of panspermia suggests extremophiles that can survive in space (such as tardigrades) may have become trapped in debris from planetary collisions then reached Earth on an asteroid. The next time you come across damp moss, beware of alien moss piglets!
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