Tardigrade

    What do you think the world’s toughest animal is? Is it a bear? How about a lion? If you guessed any land animal, you’re wrong. The world’s toughest animal is actually an extremely small organism that cannot be seen from the naked eye called a tardigrade. Tardigrades are so small, that 90,000 of them can fit into one droplet of water! Usually tardigrades are filtered out when drinking bottled water, but if you have ever drank unfiltered water (from a river or stream or something of that sort), chances are, you probably have digested over three billion tardigrades! But don’t worry about it, tardigrades are completely harmless. Right now, you may be thinking: “how could this tiny animal possibly be the toughest animal in the world?” Well, I’m glad you asked.

    Tardigrades are much tougher than you and I. For starters, they can withstand temperatures as low as -200 degrees Celsius, and as high as 304 degrees Celsius! If you thought that was impressive, then you won’t believe this next fact. Tardigrades can survive without oxygen for up to ten years. They can also withstand pressure six times greater than a human can! You know that feeling your ears get when you go high up in the air or to the very bottom of a swimming pool? Imagine the feeling being one hundred times stronger. Tardigrades are also able to withstand pressures six times the amount of the deepest parts of the ocean, that much pressure could destroy a metal ship!

    Although tardigrades thrive in water, they can go without it for two years straight. They can also go two years without anything to drink, and three years without anything to eat! Tardigrades have adapted to environmental stress by undergoing a process called cryptobiosis. Cryptobiosis is a state in which metabolic activities come to a reversible standstill. It is truly a death-like state; most organisms die by a cessation of metabolism. Several types of cryptobiosis exist, the most common include:

• anhydrobiosis (lack of water);
• cryobiosis (low temperature);
• osmobiosis (increased solute concentration, such as salt water);
• anoxybiosis (lack of oxygen).

Tardigrades can survive dry periods by curling up into a little ball called a tun. Tun formation requires metabolism and synthesis of a protective sugar known as trehalose, which moves into the cells and replaces lost water. While in a tun, their metabolism can lower to less than 0.01% of normal. Revival typically takes a few hours, depending on how long the tardigrade has been in the cryptobiotic state. The longest known time that a tardigrade has spent in this tun is one hundred years!

Vocabulary:

Tardigrade: a minute animal of the phylum Tardigrada; a water bear.

Cryptobiosis: a physiological state in which metabolic activity is reduced to an undetectable level without disappearing altogether. It is known in certain plant and animal groups adapted to survive periods of extremely dry conditions.

Anhydrobiosis: of a usually aquatic organism :  life away from water

Cryobiosis: an ametabolic state of life entered by an organism in response to adverse environmental conditions such as desiccation, freezing, and oxygen deficiency. In the cryptobiotic state, all metabolic processes stop, preventing reproduction, development, and repair

Osmobiosis: a drastic increase of a solute in a concentration

Anoxybiosis: life in the absence of free or atmospheric oxygen

Tun: A cryptobiotic state where an organism remains in a coma-like status until it is removed or removes itself

Metabolism: the chemical processes that occur within a living organism in order to maintain life.

Synthesis: combination or composition, in particular.

Trehalose: a sugar of the disaccharide class produced by some fungi, yeasts, and similar organisms.