What they are: More commonly known as “Water Bear” or “Moss Piglet”, the tardigrade is classified as an arthropod within the animal kingdom. The tardigrade’s physical traits are similar to the well-known arthropods we call “insects”. These invertebrate animals have bodies consisting of multiple sections, a skeleton external to their body, and many jointed limbs.
Environment: Tardigrades are found in any water dwelling or moisture rich environments such as fresh water lakes, oceans, or even in damp land areas; these types of environments provide the amount of water needed for water bears to remain active. Yet, water bears’ ability to adapt to many environmental pressures allow them to live in a wide variety of areas around the world. Different species of tardigrades have been known to live in extremely warm or cold environments, within the deep depths of the ocean, and upon the highest elevations of mountains.
The Life: Different environmental pressures, such as cold temperatures and low oxygen level, cause tardigrades to go into a state known as “cryptobiosis”. There are different and specific latent states of cryptobiosis that water bears enter, depending on the environmental pressure the water bears are exposed to. While in these states, the processes that occur within the water bear are temporarily reduced or stoped, allowing for resistance to environmental pressures. Being able to change states provides water bears with advantages over environmental changes.
Life Expectancy: Between 3 to 30 months is the average life expectancy of water bears in their normal state. However, the life expectancy of each individual can vary based upon periods of latent/crytopbiotic states. Life expectancy could be greatly extended or reduced based on the states of an individual tardigrade throughout its lifetime.
All of the facts are related to the tardigrade’s ability to change states in relation to environmental conditions.
Freeze Tolerance: In extremely cold conditions water bears will increase their production of proteins that act as antifreeze and agents that increase the production of ice crystals. These proteins lower the temperature that must be reached for water bears to freeze. Production of ice crystals around the outside of water bears decreases the internal stress cause by the extreme cold.
Desiccation Tolerance: Tardigrades are able to survive in dry environments byproducing various compounds. Trehalose, often found in waterproof makeup, is one compound produced by water bears that aids in the retention of water. Trehalos keeps water within the body of a tardigrade to prevent it from drying out. First Non-Human Organism in Space: In 2007, two tardigrade species were launched into space via the European Space Agency's FOTON- M3 spacecraft. Although in low orbit while in space, the species were still exposed to solar and cosmic radiation. Most of the individuals were able to conquer the high stress of the radiation by changing their cryptobiosis stages, making them the first non-human organism to arrive and survive in space.
Sources:
Nelson, Diane R. "Integrative and Comparative Biology." Current Status of the Tardigrada: Evolution and Ecology. Oxford University Press, 2015. Web. 21 Sept. 2015.
Stone, Jonathon. "Journal of Astrobiology & Outreach." Tardigrade Exposure to Outer Space Conditions. Journal of Astrobiology & Outreach, 31 Oct. 2014. Web. 21 Sept. 2015.
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