Tardigrades (Water Bears, Moss Piglets)

Tardigrades:

Tardigrades belong to the phylum Tardigrada of kingdom Animalia.

Lazzaro Spallanzani in 1777 named them Tardigradum which means "slow walker". Tardigrades are eight legged microscopic animals. They’re commonly known as water bears or moss piglets.

We have discovered 1000+ species of tardigrades till now.  The name "water-bear" comes from the way of their gait, as they look like a bear walking; Mosses and lichens are their preferred habitat hence their nickname, moss piglet.

 Tardigrades are naturally found on mountaintops, in the deep sea, in tropical rain forests and even the frigid Antarctic.

Most species are found to be living in freshwater or semiaquatic terrestrial environments. They’re considered aquatic because they need water around their bodies for gaseous exchanges as well as to prevent themselves from drying out (desiccation). 

Tardigrades are covered in a tough cuticle, similar to the exoskeletons of grasshoppers, praying mantises, and other insects to which they are related. They have four to six claws on each foot, which helps them cling to plant matter, and a mouthpart known as bucco-pharyngeal apparatus, which helps to suck nutrients from plants and microorganisms.

                   

 

Tiny, tough and resilient:

Tardigrades belong to an elite category of animals known as extremophiles (or critters). They can live at temperatures as cold as absolute zero or above boiling, at pressures six times that of the ocean’s deepest trenches, and even in the vacuum of space. They can even survive up to 30 years without food or water.  

In 2007, scientists discovered the water bears can survive an extended stay in the highly radioactive vacuum of outer space.

A European team of researchers sent a group of living tardigrades to orbit the earth on the outside of a FOTON-M3 rocket for 10 days.

When the water bears returned to Earth, the scientists discovered that 68% lived through the ordeal. Their resiliency is in part due to a unique protein in their bodies called D-sup (Damage - suppresor protein) which protects their DNA from being harmed by ionizing radiation present in soil, water, and vegetation.

Cryptobiosis in tardigrades:

Another amazing survival trick that water bears have down their sleeves is cryptobiosis, a state of inactivity which is triggered in a dry environment. They shrivel up, losing all but around 3% of their body's water and slow down their metabolism down to just 0.01 % of its normal rate.

In this state, the tardigrade just persists against the conditions, doing nothing, until it's exposed to water again. When that happens, the creature pops back to life like a re-wetted sponge and continues onward as if nothing had happened.

How are tardigrades useful to us?

Tardigrades can survive being in cryptobiosis for more a decade. According to some researchers some species of tardigrades might even be able to survive desiccation for up to a century.

Yet the average lifespan of a (continuously hydrated) tardigrade is rarely longer than a few months.

If we humans can replicate cryptobiosis in the way tardigrades do, we'd live far longer than the average life expectancy which might prove helpful in future interstellar travels.