Tardigrades - The Amazing Water Bear!

The Water Bear:  

Toughest Animal Alive!!

The tardigrades, or water bears, have to be one of the most amazing creatures on this Earth.  I thought about them just this week in my biology class when we were discussing two evolutionary problems that had to be solved before plants and animals could colonize the land masses (dehydration and reproduction).  While thinking about dehydration, I mentioned the water bears to my classes.  I try to throw out fun factoids to my students whenever possible.  My students love hearing snippets of amazing "science stuff" and I love how it stimulates their scientific curiosity.  The mention of water bears caused a ripple of questions by my students, so I did a bit more research in order to satisfy their curiosity.

The Amazing Facts About Water Bears!

(Drum roll, please!)

• Tardigrades are commonly called "water bears" or "moss piglets".  They look like chubby little microscopic bears!
• They are animals with 8 legs. Each leg ends with 4 to 8 claws.
• They are very small.  They range in size from a quarter of a millimeter to a half a millimeter.
• Tardigrades are the toughest animal around. They can survive in extreme environments that would kill almost any other animal.
• Tardigrades are famous for their ability to perform "cryptobiosis". They can survive for years without water.  Normally their body is 85% water.  Their body composition can drop from 85% water down to 3% water and still survive.

• They can spend years in this dehydrated state.
• While in a dehydrated state, the metabolic rate drops to .01% of normal.
• They can survive extreme temperatures.  They have been known to survive in temperatures as low as -273 degrees Celsius and as high as 151 degrees Celsius.
• They can survive 1000 times more radiation than any other animal.
• Tardigrades are the first known animals that can survive the vacuum of space!  Tardigrades have returned alive when exposed to the vacuum of space for a few days in low Earth orbit.
• They can remain in the state of suspended animation for years. When placed in water, they become active again.
• Tardigrades can survive in the extremely low pressure of a vacuum as well as high pressure of 1200 atmospheres.

• Tardigrades have been discovered in hot springs, on top of the Himalayas, and under layers of solid ice.  
• They may be found living on land or in fresh or salt water.
• They belong to the phylum Tardigrada and the superphylum Ecdysozoa.
• Their body is covered with a cuticle composed of chitin.  They molt periodically.

Here is a fun idea that I am going to try.  (I just read about this on the internet, and I am definitely going to give this a try!!)  Collect a few samples of moss.  You might ask your students to bring in samples that they find around their homes.  Soak the moss in a Petri dish for a few hours. Remove the moss and place the Petri dish under a dissecting microscope. You should find water bears!

Here is a pretty amazing video that I found on youtube.  This will definitely get the attention of your biology students!

Have fun teaching!!