Here at 360 on History we find tardigrades – also known as water bears – very very cool. These eight-legged extremophiles (organisms that live in extreme environments, under high pressure and temperature) are invertebrates related to arthropods (e.g., crustaceans and insects) and nematodes (e.g roundworms).
Extremophiles first evolved more than 40 million years ago and have continued to not only survive but thrive in the most extreme conditions this planet can provide. This ability has made them one of the most abundant lifeforms on Earth.
And tardigrades are the granddaddies of extermophile! They were first described in 1773 and have been found everywhere from mountaintops, to the deep sea and mud-volcanoes, from tropical rainforests to even Antarctica. But that’s not the only cool thing about them, They are also one of the most resilient animals known; able to survive exposure to even the most extreme conditions, such as extreme (both high and low) temperature and pressure, radiation, and dehydration. Deprive them of air and water and they will survive that too. Not only that, they have also lived after being exposed to outer-space! They can do this partly because of the shielding provided by a special ‘damage suppression’ protein called Dsup.
Tardigrades are usually about 0.5 mm (0.02 in) long when fully grown and have claws at the end of each of their eight legs. They are probably the smallest animals with legs, and one of the only soft-bodied animals that can walk. But we did not really know how they walked. Well, we do now. Scientist Jasmine A. Nirody and colleagues decided to find out. They recorded walking tardigrades of the species Hypsibius dujardini to analyze their gait and leg coordination, using high-speed video of the animals walking on gel substrates and on glass. They published their results (and the videos) in a study.
What they saw was tardigrades walking around by utilizing “a tetrapod-like stepping pattern remarkably similar to that observed in insects, despite significant disparities in size and skeletal structure between the two groups“. Plus, they also “adapt their locomotion to a “galloping” coordination pattern when walking on softer substrates” – similar to arthropods. Check this out in the video, you will love it!
Oh and one more thing. In 2019, Israeli spacecraft Beresheet tried to land on the Moon. On board it had tardigrades. Unfortunately, the spacecraft crashed on the lunar surface. The mission’s founder was of the opinion that its disk, as well as the tardigrades survived. Now considering that these creatures are so hardy, dare we think they are hanging about on the surface of the Moon, waiting to be awakened from their suspended animation state? Who knows.