The (almost immortal) animal of the day



Name : Tardigrades (Tardigrada) are a phylum within the animal kingdom. Also known as water bears, they are thrown together with arthropodes and velvet worms to form the clade of the panathorpodes. They are especially known for their  ability to adapt  and their extraordinary resistance.

Habitat : They can be found among lichen and mosses but also in the sand and on the sediments. Simply put, they can be found everywhere on Earth (who knows, there might be one in your backyard) !

Size : The adult size of tardigrades can vary between 0,1 mm and 1,5 mm depending on the species. Hence, it’s impossible to see them with the naked eye.

Way of life : Aquatic tardigrades live from 12 to 24 months, while terrestrial species live from 15 to 30 months. However, in reality this corresponds to their active lifespan, without cryptobiosis. Indeed, cryptobiosis periods give them the ability to survive for a far longer time. Their favourite food is lichen and nematodes. Little is known about their method of reproduction.


Possessing eight clawed legs, the tardigrade has a peculiar aspect. He has a short head and his mouth possesses a circular row of teeth. His body is covered with a cuticle. His last leg is directed backwards. This thus enables him to hang in a variety of acrobatic positions.

The interesting part about this species is not its anatomy, but rather its capacity to survive in the most extremes of conditions. Those famous water bears are called “extremophile”. They can resist the higher pressure of the seabed and temperatures ranging from absolute zero to 150 °C. They are found in the highest peaks and even in the most arid of deserts. However that is not all, they are resistant to numerous radiations, such as X-rays or ultraviolets, to a lack of oxygen and even to dehydration. They could even survive in space and repair their own DNA.

This incredible resistance can be explained by its capacity to enter cryptobiosis. They greatly reduce their metabolic process. This enables them to survive in even the harshest of conditions. Tardigrades can wait indefinitely in this cryptobiotic state while waiting for conditions to become more tolerable.
Tardigrades fascinates researchers and biologists because they are behind important advances in many fields. Indeed, studies have shown some tardigrade genes could potentially be transferred into human cells. This could be quite interesting in the field of cancerology, but also in the wider medical field (diabetes, Parkinson’s Disease for instance).

Article written by Alizée Fernandes Pereira
Translated by Matthias RUDEANU

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