Tardigrade
A half-millimeter animal that survives the vacuum of space, boiling water, and 150 years of being completely dry
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Superpower
Tardigrades enter a state called cryptobiosis — expelling almost all body water, pulling their legs inside, contracting into a barrel shape called a tun, and reducing metabolism to 0.01% of normal. In this state they survive: temperatures from -273°C to 150°C, pressure from deep ocean trenches to six times that, ionizing radiation doses 1,000 times the human lethal dose, complete vacuum, and desiccation lasting up to 150 years. When rehydrated, they unfurl, resume walking, and begin eating within hours.
Overview
Tardigrades (meaning 'slow steppers') are microscopic eight-legged animals found in every habitat on Earth — from mountaintops to deep ocean trenches, Antarctic ice to tropical rainforests, and every garden with moss or lichen. Over 1,300 species are known. They were first described in 1773 and placed in their own phylum (Tardigrada). They eat by piercing plant cells and algae with stylets and sucking out the contents. They've been exposed to open space on the exterior of spacecraft and survived. They are almost certainly the most indestructible animals on Earth — yet they're present in virtually every patch of damp moss in the world.
Found in
Every terrestrial, freshwater, and marine environment on Earth — the most geographically widespread animal phylum. Most abundant in moss, lichen, and leaf litter where thin films of water collect. Present at every altitude and depth where moss or biofilm exists.
Things worth knowing
- 1
Tardigrades were exposed to outer space on the FOTON-M3 mission in 2007 — vacuum, cosmic radiation, and solar UV — for 10 days. A significant proportion survived and reproduced normally afterward.
- 2
Their radiation resistance comes partly from a unique protein (Dsup — 'damage suppressor') that physically wraps around DNA and absorbs radiation hits before they can cause strand breaks. Human cells engineered to express Dsup show 40% less DNA damage under radiation.
- 3
A tardigrade's four pairs of legs end in claws or sucking discs and are unjointed — they're more like stumps with attachments than true arthropod legs, placing tardigrades in their own evolutionary position near the arthropod ancestor.
- 4
Tardigrades in cryptobiosis can be revived after 150 years of being completely dried out. A 2016 study successfully revived specimens from Antarctic moss samples collected in 1983 — 30 years of desiccated dormancy.
- 5
Despite surviving conditions lethal to virtually every other animal, tardigrades are not immune to all threats — they're quite vulnerable to prolonged high temperatures when active (above ~35°C in moist conditions). Their superpower is dormancy, not invincibility.