Tardigrades: Nothing to do with Being Late

     Tardigrades have nothing to do with being late to school, though biology students often study these tiny invertebrates with a low-powered microscope. Tardigrades are also known as water bears or moss piglets:

      The critters, which average .5 mm long, were discovered in 1773 and are nick-named for their resemblance to bears, though their taxonomic name, Tardigrada, translates to "slow stepper." 

     Tardigrades thrive in moss, lichen, lakeshores, and other moist environments though they are also found in extreme environments like deserts, deep ocean trenches, and in high tree tops. Water bears have a full alimentary canal and digestive system. Mouth parts and a sucking pharynx (see Scanning Electron Microscope (SEM) image below) 

  

lead to an esophagus, stomach, intestine and anus. They have well-developed muscles and a single gonad. Tardigrades have a dorsal brain atop a paired ventral nervous system.

     Tardigrades can withstand temperatures from just above absolute zero to nearly 100 degrees F above the boiling point of water, pressures about 6 times greater than those found in deep ocean trenches, being plunged in rubbing alcohol, ionizing radiation at doses hundreds of times higher than the lethal dose for humans, and the vacuum of outer space:

     Water bears can go without food or water for more than ten years, drying out to the point where they are 3% or less water in a process known as cryptobiosis. It astounds me to think of something with a brain and nervous system being able to curl up into a ball for years, lose most of their water content, and still survive. They can then rehydrate and just carry on normal lives. 

     Water bears have been around since the Cambrian period, surviving major extinctions at the end of the Paleozoic and Mesozoic time periods. There are over 1000 species of tardigrades, most with 8 claws or disks:

     Bob Goldstein from the U of North Carolina, who has done SEMinal (pun intended) research on the little beasts, says of water bears, “There’s one thing that we know of, which is some animals that survive drying make a sugar called trehalose.” He continued, “And trehalose sort of replaces water as they dry down, so it will make glassy surfaces where normally water would be sitting. That probably helps prevent a lot of the damage that normally occurs when you dry something down or when you rehydrate it.” Not all of the >1,000 species of water bears produce this sugar though, he says, so there must be some other mechanism involved.

     This 3-minute clip on Water Bear Research shows the moss piglets in a state of cryptobiosis, in some of their environments, as well as disabled students climbing trees from and in wheelchairs to discover new species of tardigrades. 

    Neal DeGrasse Tyson featured tardigrades this spring on Cosmos. Are they old friends of yours or new acquaintances?

Better late to the tardi(grade) than never, 

Steph

(Word Woman)

Guess what is in these two false-colored SEM images:

                     

                SEM IMAGE 1

                 SEM IMAGE 2

And for comparison, the same thing without magnification:

Aren't fractal veggies cool?

And one more in black and white:

                        SEM IMAGE 3

Those mathematicians can be vicious: