What the World's Toughest Animal Is Really Made Of

Scientists investigating the genome of a tiny aquatic invertebrate called the tardigrade, or water bear, made a very peculiar discovery.

When humans are resilient, we say they’re made of sterner stuff.

But they've got nothing on tardigrades, tiny water-dwelling invertebrates that are considered the most robust animals on Earth.

Not only can the tough little guys—also known by the nicknames water bear and moss piglet—withstand freezing temperatures, long periods of drought, and high doses of radiation, they're the only animals known to have survived the vacuum of space.

That made us here at Saturday’s Weird Animal Question of the Week wonder—just what are these microscopic diehards made of?

Like everything about the tardigrade, the answer is startling.

Tardigrades have a huge amount—17.5 percent—of foreign DNA, a new study says.

A team sequenced the genome of a tardigrade species Hypsibius dujardini "to try to

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