Imagine a being that can thrive in extremely complex environments; in an environment beyond our imagination. That’s right, folks! I am talking about an organism that loiters in regions of composite conditions like in a volcano, vacuum of space and the like. Nothing could cease its existence. The organism which I am talking about is called a tardigrade, whom we simply refer to as a water bear or moss piglets. Hard to believe, right? I, too, was shocked when I first found out about them.
Tardigrades are tiny organisms that can be observed only under a microscope. Short in size, their dimensions vary between 0.5mm and 1.2 mm in body length. These eight-legged creatures belong to the kingdom Animalia and subkingdom Eumetazoa. Belonging to the Phylum Tardigrada, they are invertebrates and related to arthropods and nematodes. Tardigrades are heterotrophs that consume plant/animal cells and bacteria. They were discovered by German Pastor J.A.E. Goeze in 1773 and were later given the name Tardigrada by Italian Biologist Lazzaro Spallanzani. Fascinating, aren’t they? It is said that there are 1300 different species of tardigrades on our planet. Tardigrades are unique creatures on their own. They are champions of space radiation. Space radiation is immensely harmful to living organisms as it can destroy molecules and DNA at a rate faster than it can be repaired but these creatures are known to remain unaffected.
Now the question is, how do they remain alive in such harsh conditions?
Tardigrades are known to adapt to high levels of environmental stress through a process which is known as Cryptobiosis. Cryptobiosis is characterized as a reversible state in which metabolic activity can come to a halt. It is genuinely a death-like state; most organisms die when their metabolism stops working. There are various Cryptobiosis, but the most common ones are:
- Anhydrobiosis (lack of water)
- Cryobiosis (low temperature)
- Osmobiosis (increased solute concentration, such as saltwater)
- Anoxybiosis (lack of oxygen)
Anhydrobiosis is the most common kind of cryptobiosis studied in tardigrades. In 1702, Anton van Leeuwenhoek discovered minute animalcules in dirt gathered from house roofs, which he named cryptobiosis. When he dried them out and reapplied water, the animals began to move around again. Nematodes or rotifers, or other cryptobiotic creatures, were most likely the animalcules. Tardigrades may withstand periods of drought by rolling up into a little ball known as a tun. Tun creation necessitates the metabolism and production of trehalose, a protecting sugar that goes into cells and replenishes lost water. Their metabolism can drop to less than 0.01 per cent of normal while in a tun. Depending on how long the tardigrade has been in the cryptobiotic stage, restoration can take a few hours.
But every being has a weakness, and so do tardigrades.
Tardigrades do adapt to difficult environments but their survival rate diminishes the longer they are present in those difficult environments. In a study, it was also seen that Tardigrades are fatal to heat over time. Acclimation (the process of adapting to a new environment) helped the tiny organism to an extremely low extent. Their survival also depends on their current state, depending on whether they are in the active or tun state. The study results weren’t significant as there are over 1000+ species of tardigrades known to live and this might not apply to all of them.
Tardigrades are strong beings. Their body and structure act in a mysterious way. These creatures never tend to amaze us. A lot of information about them is still to be dawned upon us. That’s all for now! We’ll get back to you with more interesting stuff like this.
Stay Tuned!
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