Tardigrades Information and facts


Tardigrades, often called water bears or moss piglets, are near-microscopic animals with long, plump bodies and scrunched-up heads. They have eight legs, and hands with four to eight claws on each. While strangely cute, these tiny animals are almost indestructible and can even survive in outer space.

Size

These creatures look like the hookah-smoking caterpillar from "Alice in Wonderland." They can range from 0.05 millimeters to 1.2 mm (0.002 to 0.05 inches) long, but they usually don't get any bigger than 1 mm (0.04 inches) long.

diet


Tardigrades eat fluid to survive. They suck the juices from algae, lichens and moss.

habits

Tardigrades were discovered by a German pastor, Johann August Ephraim Goeze, in 1773. He named them Tardigrada, which means "slow stepper." In 1776, Italian clergyman and biologist Lazzaro Spallanzani discovered that water bears survive extreme conditions by making a transformation. 

In many conditions, they survive by going into an almost death-like state called cryptobiosis. They curl into a dehydrated ball, called a tun, by retracting their head and legs. If reintroduced to water, the tardigrade can come back to life in just a few hours.  

While in cryptobiosis, tardigrades' metabolic activity gets as low as 0.01 percent of normal levels, and their organs are protected by a sugary gel called trehalose. They also seem to make a large amount of antioxidants, which may be another way to protect vital organs. Water bears also produce a protein that protects their DNA from radiation damage, according to research by the University of Tokyo.

Tardigrades have been experimentally subjected to temperatures of 0.05 kelvins (–272.95 degrees Celsius or functional absolute zero) for 20 hours, then warmed, rehydrated and returned to active life. They have been stored at –200 degrees Celsius for 20 months and have survived. They have been exposed to 150 Celsius, far above the boiling point of water, and have been revived. They have been subjected to more than 40,000 kilopascals of pressure and excess concentrations of suffocating gasses (carbon monoxide, carbon dioxide, nitrogen, sulfur dioxide), and still they returned to active life. In the cryptobiotic state, the animals even survived the burning ultraviolet radiation of space.

Challenging student scientists to ponder the astonishing durability of tardigrades brings their understanding of physics, chemistry and biology into play. They recall that water expands as it approaches the freezing point, which is why ice floats. At 4 degrees celsius the expansion of water exerts sufficient force to split boulders, rupture metal containers and explode living cells. A cell is more than 95 percent water. The rupturing forces and icy microshards that form in frozen cells are the same that cause frost bite.

 Offspring

Tardigrades reproduce through sexual and asexual reproduction, depending on the species. They lay one to 30 eggs at a time. During sexual reproduction, the female will lay the eggs and the males will fertilize them. In asexual reproduction, the female will lay the eggs and then they will develop without fertilization. 

other facts



The water bear's mouth can telescope outward to reveal sharp teeth that are used to grab onto food.

They swim! Their multiple legs propel water bears forward to reach food.

Tardigrades must have at least a thin coating of water around their bodies to prevent turning into a tun.

Classification/taxonomy 
Here is the classification for tardigrades, according to ITIS:

Kingdom: Animalia
Subkingdom: Bilateria
Infrakingdom: Protostomia
Superphylum: Ecdysozoa
Phylum: Tardigrada


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