認識緩步動物：抵抗太空、高溫和輻射的微型超級倖存者！

Tardigrades, also known as water bears or moss piglets, are some of the most resilient creatures on Earth. These tiny animals, measuring only about 1 millimeter long, have amazed scientists with their ability to survive in extreme environments. Tardigrades can withstand being baked, frozen, shot from a gun, and even sent into outer space. Some experts believe that tardigrades could outlive all other species, including humans, and survive until the Sun dies.

Under a microscope, tardigrades look quite unusual. They have pudgy faces, sharp claws, and teeth that resemble daggers, making them appear more like monsters than animals. Despite their odd appearance, tardigrades are closely related to arthropods, such as insects and crustaceans. They are commonly found in places with moss, lichen, and leaves, and you might even spot them in your backyard. However, they are also known for surviving in harsh environments, such as high mountains, deep oceans, and acidic hot springs. In 2007, tardigrades became the first known animals to survive being sent into space. Some of the females even laid eggs while in space, and the young hatched healthy.

Scientists have conducted many experiments to test the limits of tardigrades. These creatures can survive temperatures as high as 150 degrees Celsius and as low as minus 272 degrees Celsius. In one experiment, tardigrades were fired from a gun at speeds faster than a bullet, and many survived. Tardigrades have developed several survival strategies. When they dry out, they enter a state called a tun, where their metabolism slows down to almost nothing. In this state, they can remain dormant for decades and revive when exposed to water.

One of the secrets to their survival is the production of special proteins called TDPs (tardigrade-specific intrinsically disordered proteins). These proteins help protect their cells when they dry out by forming a gel-like substance that cushions the cell contents. Other animals, like tree frogs and brine shrimp, use a sugar called trehalose for similar protection, but tardigrades rely on TDPs.

Tardigrades can also survive extreme heat, but only when they are in their tun state. If they are exposed to high temperatures while active, they die like other organisms. This suggests that even tardigrades are vulnerable to climate change. Some studies show that tardigrades can boost soil health by eating other tiny creatures.

Tardigrades have other ways to survive freezing, radiation, and low-oxygen conditions. For example, they can enter a state called anhydrobiosis, which allows them to survive without water. They also produce a protein called Dsup (damage-suppressor protein) that wraps around their DNA and protects it from radiation. Scientists have even engineered human cells to produce Dsup, making them more resistant to radiation.

Researchers are exploring how tardigrade proteins could help humans. For instance, Dsup might protect cancer patients from the harmful effects of radiation therapy. TDPs could help preserve vaccines and medicines that need to be stored for long periods. NASA is interested in using tardigrade survival strategies to protect food and medicine during space missions.

The reason tardigrades have evolved these abilities is still a mystery. One theory is that because they are so small, they can be carried by the wind to different environments, so they need to be able to survive many types of stress. By studying tardigrades, scientists hope to find new ways to help humans and protect the environment. Tardigrades remind us that even the tiniest creatures can teach us important lessons about survival.