The tardigrade... often commonly called a water bear or moss piglet) is a very small but very interesting creature. My son spent the whole of last week telling anyone who would listen about "the toughest creatures on Earth"!
These little animals are usually about 0.5 to 1.2 milimetres in length, which means they are may be just visible to the naked eye but can easily be viewed under a low powered microscope. They are water dwelling organisms found in both marine and freshwater habitats. They are commonly found on lichens and mosses and must be surrounded by a film of water to prevent them from drying out. Tardigrades can be found in every continent of the world and in some very extreme enviornments.
These water bears are very cute little microscopic creatures, they have short, plump, segmented bodies with four pairs of lobopodial limbs (poorly articulated) with four to eight claws at the end of each. These small invertebrates move in a slow lumbering fashion, hence the name water bear.
Tardigrades feed on the fluids of plant or animal cells. Some species are even know to feed on other tardigrades. They pierce the cell wall and then ingest the fluid via a sucking pharynx.
There are a number of amazing features about these micro animals that have made them the interest of many studies over the years....
Tardigrades are extremophiles:
They can (for a short period of time) survive extremes of temperatures from -200 up to 150 degrees Celcius;
They can withstand pressures up to 1,200 times atmospheric pressure or the very low pressures of a vacuum;
They can withstand extreme levels of radiation - up to 1000 times the levels that would be lethal to most animals;
When exposed to environmental extremes they reduce their metabolic rate down (just 0.01%) to an almost death-like state called cryptobiosis.
In 2008 a number of tardigrades were launched into outer space for ten days where they were exposed to extremes of temperature, UV radiation from the Sun, the vacuum of space and dehydration. Amazingly, some of these creatures survived the ordeal and even went on to successfully reproduce.
They are the only creatures able to survive being photographed by a Scanning Electron Microscope (SEM) (which bombards them with a stream of electrons while placed within a vacuum).
It is easy to see now what my son was talking about; I am as impressed with these little creatures as he is. I imagine we will be going on a "Tardigrade Hunt" before the Summer holidays are out and we will see how they look under our family microscope.
If we have any luck I will be sure to share it all here!