Tardigrades are an amazing species of micro-animal that is known for recovering after being exposed to harsh environments. They are found in damp moss and in dewdrops. They have survived the last 5 mass extinctions. Looks like we have a bit to learn from the hardy water bear. 🙂
Anatomy:
Tardigrades are eukaryotic organisms, which means that their cells have a nucleus, just like in our cells. Eukaryotes tend to be more complex. They look a bit like an eight-legged maggot with wispy claws on the end and a circular mouth. In some species, the mouth extends outward, zenomorph-style. They do have an anus, like most animals do, and are renowned for their wondrous poops.
Distribution:
Tardigrades are found all over the world in damp environments. Tardigrades are capable of surviving environments that have changed relatively quickly. This is probably why tardies have survived the last 5 mass extinctions. Though environmentally resistant, they are not technically extremophiles. Tardigrades, water bears, or moss piglets, are very tolerant (at least temporarily) in many extreme environments; because of this fact, they are often misnomered as extremophiles. They don't thrive in extreme environments (such as on the moon). There are over 1150 species of tardigrade. See the family tree here. A new species has recently been found in Japan. https://news.nationalgeographic.com/2018/03/tardigrade-water-bear-parking-lot-japan-spd/
Tardies can withstand high temperatures, arid environments, freezing cold, dangerous radiation (enough to kill a human), and the intense vacuum of space. The record, in which a tardigrade retained the ability to reproduce after direct space exposure was 10 days. Tardigrades have the ability to form a hard cyst when exposed to extreme environments and remain dormant until the environment is more favorable. Though they suffer some DNA damage in space, water bears have special proteins that protect the integrity of their DNA. Their DNA repair mechanisms are being researched as possible insight into applications for cryogenics, cryonics, and radiation resistance in humans. There was a study investigating whether we can transfer the proteins that offer DNA protection in tardigrades, into human cultures to see if similar protective activity is shown, it was https://lnkd.in/dwh4m_8
Lifecycle:
The life cycle for tardigrades is similar in most species. They either reproduce sexually or via parthenogenesis (virgin life creating). They lay eggs in or on a substrate and tend to abandon them. The eggs usually hatch in about 14 days. Tardigrades molt about 14 times before adulthood and may live as long as 200 years in perfect conditions; however, they can go into a suspended form and be revived later. Scientists aren’t certain how long tardigrades can remain in this preserved form but factors such as just how much dryness, salination, radiation, etc is present all play a role in survivability. Numbers have ranged from a few hundred years to thousands and possibly even billions depending on the frequency of dormancy and environmental variables.
At one point, it was considered that tardigrades must be alien due to some unique genetic markers and proteins. But no, tardies are alien-like, but not aliens. Tardigrades evolved here on Earth possessing unique traits that have helped it survive for over 500 million years. We indeed are still learning new and amazing things about our micro-animal cousins. Perhaps, discoveries today could pave the way to deep space / extended travel for humans in the future.
Video:
Tardigrades in The Media:
1.) The Cosmos series Episode 2:
2.) SouthPark: NSFW or Children (but hilarious): Moss Piglets
3.) Tardigrades crashed on the moon? yes, but despite the hype, they will not survive.