Tardigrades: The Toughest Animals on Earth
They are barely visible to the naked eye, they live in the moss on your roof, and they may be the most indestructible animals ever discovered. Meet the tardigrade — affectionately known as the "water bear" or "moss piglet" — a microscopic creature that has survived conditions that would obliterate almost anything else alive, including a trip into open space.
Meet the Water Bear
Tardigrades are tiny eight-legged animals, typically under a millimetre long, that lumber through droplets of water on mosses, lichens, soil, and seabeds worldwide. Under a microscope they really do resemble plump, clawed bears ambling in slow motion. Ordinary in appearance — extraordinary in resilience.
The Secret: Becoming Glass
Their superpower is a survival trick called cryptobiosis. When their world dries out or turns deadly, a tardigrade pulls in its legs, expels almost all the water from its body, and curls into a barrel-shaped husk called a tun. Inside its cells the contents thicken and set like glass, and its metabolism falls to something very close to zero — effectively pausing life itself (The Scientist). In this state it can wait, sometimes for years, until water returns and revives it.
Tested to the Extreme — and Into Space
In the tun state, tardigrades have endured almost unbelievable punishment: temperatures from around −237 °C to over 150 °C, pressures several times greater than the deepest ocean, and intense radiation. Most famously, on the 2007 FOTON-M3 mission they became the first animals known to survive direct exposure to the vacuum of space, along with its cosmic and ultraviolet radiation (Wikipedia — Tardigrades in space).
The Molecular Toolkit
Scientists are now uncovering how they do it. Tardigrades produce a protein nicknamed Dsup ("damage suppressor") that physically shields their DNA from radiation, and special CAHS proteins that form a protective gel as the animal dries, cushioning its cellular machinery. Researchers hope these molecules could one day help protect human cells, stabilise medicines without refrigeration, or safeguard astronauts.
Key Takeaways
- Tardigrades are microscopic eight-legged animals found in moss, soil, and water worldwide.
- Via cryptobiosis they dry into a "tun," nearly halting their metabolism.
- They have survived extreme heat, cold, pressure, radiation, and the vacuum of space.
- Proteins like Dsup and CAHS underpin their resilience and inspire medical research.
Frequently Asked Questions
Can tardigrades really survive in space? Yes — in 2007 they became the first animals shown to survive exposure to space vacuum and radiation.
Are tardigrades immortal? No. They can pause life in the tun state for long periods, but they die under sustained lethal conditions.
Where can I find them? In damp moss and lichen almost anywhere — though you need a microscope to see them.
The toughest animal on Earth is one you have almost certainly walked past without noticing. Discover more astonishing creatures in the Creature Atlas encyclopedia.