Tardigrades are small animals ranging in length from 0.1 to1.2 millimetres. Tardigrades live all over the world, from the deep sea bed to the Himalayas and from the tropics to the poles. Because they are so small they can be blown around the world in the wind like particles of dust. This means that terrestrial species can be found distributed all around the world.
Like "higher" animals they have digestive, excretory, and nervous systems; separate sexes; and well-developed muscles. Like "lower" animals, they lack respiratory and circulatory systems, instead, they breathe through their skin or cuticle and the whole body acts as a pump to circulate fluids.
Tardigrades are what is called eutelic, meaning there is a fixed number of cells in the body of an adult of any given species, this is normally around 40,000 cells. They have a relatively large brain and a well developed nervous system with a double suboesophagal ganglia and 4 further ganglia along the body. Being small they have no need of and therefore no gaseous exchange system and no blood system.
Tardigrades are survivors par excellence, the best in the animal kingdom. They can survive many environmental extremes by converting themselves into a 'tun'. This involves them pulling in their legs to give their body a cylindrical shape and then shutting down all their metabolism. Any other animal that is exhibiting zero metabolism is considered to be dead. Only tardigrades regularly return to life again from this state.
They perform this miracle by replacing the water in their membrane lipids with a sugar called trehalose. Different species have different survival characteristics and not all species form a tun, deep sea species, which can survive pressures as great as 6000 atmospheres for instance do not. (BTW, from my calculations 6000 atmospheres = 88,200 PSI or pounds per square inch!!!)
Other species have been known to survive temperatures as low as -272 C for a few minutes which is as close to absolute zero as you ever want to get, colder than outer space. They have also survived temperatures as low as -200 for more than 20 days or months. Other species can go to the other extreme and survive temperatures as high as 125C well above the boiling point of water. Still others survive doses of X-rays 250 times greater than that which would kill a mammal.
Tardigrades are the only animals that can survive having their photo taken in an Scanning Electron Microscope which involves placing them in a vacuum and then bombarding them with electrons. Species which survive periods of drought i.e. extreme dehydration have been revived after lying dormant for 120 years amongst the dried mosses in a botanical museum. There is no doubt that tardigrades could travel to the stars amongst the dust on a piece of rock were the earth ever to be destroyed. Scientists don't really know what their limits are but we do know they are the toughest animals alive for sure.
Despite these "capabilities", tardigrades are still little understood. In the 200 years since the waterbear was first described, we have not identified any specific medical, commercial, or environmental effect of tardigrades.
Despite these "capabilities", tardigrades are still little understood.
In the 200 years since the waterbear was first described, we had not
identified any specific medical, commercial, or environmental effect of tardigrades.
Originally posted by Dasher
first, i have to say that i still see too many flaws in evolution to have faith in it, but i can say that i at least try to be open minded about "God's ways."
i think that this species is a good place to look for evolutionary consistencies, or fallacies. they could either defy all known understanding of evolution or establish a "seeds of life" theory. very interesting creature and thread.
Originally posted by mOjOm
I'm glad you liked the reference to Moss Piglet Taoism. I also find it to be yet another amusing & serendipitous clue toward understanding the deeper aspects of things. Irony can make a great sign post on the road of life. Showing those who are paying attention the grand magnificents to be found even in the smallest of things.
Originally posted by I See You
You watched Animal Planet the other night too huh? I'm a waterplant operator and have seen them in raw water samples before. They are amazing.
They can survive many environmental extremes by converting themselves into a 'tun'. This involves them pulling in their legs to give their body a cylindrical shape and then shutting down all their metabolism. Any other animal that is exhibiting zero metabolism is considered to be dead. Only tardigrades regularly return to life again from this state.
Already in the 1920s Ernst Marcus suspected glue mechanisms as he noted that some tardigrades appeared to trail sand grains linked to them with tiny fibers, similar to spider net fibers. He reported as well that the tardigrades used the sand grains to clean their body from surplus glue. So the sand grains are not only forming the maritime tardigrade living room but also serve as indispensible cleaning media.