9
TARDIGRADES
PHYLUM
TARDIGRADA
Lifespan: ten years or more
Size: 0.004–0.06 inches
(0.1–1.5 millimeters)
ALIENS
People have suggested
tardigrades might be
aliens from another
planet. But as they can
go without oxygen for
only a few days, this
isn’t likely.
SURVIVORS
Tardigrades can
survive pressure
almost six times
greater than that found
in the deepest ocean
trenches.
PUFFED UP
When starved of oxygen,
tardigrades swell up
(above)
until oxygen
levels return to normal.
This puffy state is called
anoxybiosis.
TARDIGRADES
The tiny tardigrade, or water bear, clambers through
damp plants, eating tinier animals or algae with its pump-
action snout. And it’s the toughest animal ever! In tests
it has survived being boiled, frozen, pressurized, oxygen-
starved, and blitzed with radiation. But its best trick, used
when there’s no water, is to go into a tun state, where it
shrivels like a dry sponge and simply waits—for years,
sometimes—to be wet again.
