Water Bears Can Survive Being Boiled and Frozen

The incredible resilience of the tardigrade, or water bear, stems from its ability to enter a death-like state of suspended animation known as cryptobiosis. When faced with life-threatening environmental changes, such as extreme heat or cold, these microscopic invertebrates can contract into a desiccated ball called a "tun". In this state, their metabolism slows to a near-complete standstill, allowing them to endure conditions that would be instantly fatal to almost any other life form. This remarkable adaptation is not a recent evolutionary quirk; evidence suggests it may have developed hundreds of millions of years ago, potentially allowing these creatures to survive multiple mass extinctions.

The secret to this survival superpower lies in a process called anhydrobiosis, where the tardigrade expels up to 98% of its body's water. To prevent cellular collapse and fatal damage during this dehydration, they produce unique proteins that transform their cellular fluid into a protective, glass-like substance. This vitrified state holds essential molecules and organelles in place, preventing them from denaturing or rupturing, which is especially critical in freezing temperatures where ice crystal formation would typically shred cells. First noted by scientists in the 19th century, this ability allows certain species to withstand temperatures ranging from a scorching 151 degrees Celsius down to a frigid minus 272 degrees Celsius, just a single degree above absolute zero.