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'''Tardigrades''' are invertebrate microscopic animals popularly known as '''water bears'''. These organisms measure between 0.3 mm and 0.5 mm, although some can reach up to 1 mm. They are characterised by a cylindrical body, segmented into four pairs of legs with claws at the ends. | '''Tardigrades''' are invertebrate microscopic animals popularly known as '''water bears''' and notorious for their incredible ability to survive in extreme conditions. These organisms measure between 0.3 mm and 0.5 mm, although some can reach up to 1 mm. They are characterised by a cylindrical body, segmented into four pairs of legs with claws at the ends. | ||
Their body is covered by an external cuticle, which they shed periodically. They are bilaterally symmetrical and have a complete digestive system, but lack a respiratory and circulatory system. Instead, they obtain oxygen by diffusion through their skin. They are aquatic animals and live in humid enviromets such as '''mosses''', lichens, wet soils and even in seawater and freshwater, where they feed on plant cells or small invertebrates.[[File:Istockphoto-1295483613-612x612.jpg|thumb]]They have become truly remarkable for their '''high resistance''' to extreme environments such as freezing at temperatures close to absolute zero, high temperatures up to 150°C, extreme dehydration, starvation for decades, high levels of radiation and space vacuum, extreme pressures, both high and low... This is made possible by their ability to shut down their organs and stop their metabolism when environmental conditions are not suitable (this is called '''cryptobiosis''') and come back to life when optimal conditions are restored. | Their body is covered by an external cuticle, which they shed periodically. They are bilaterally symmetrical and have a complete digestive system, but lack a respiratory and circulatory system. Instead, they obtain oxygen by diffusion through their skin. They are aquatic animals and live in humid enviromets such as '''mosses''', lichens, wet soils and even in seawater and freshwater, where they feed on plant cells or small invertebrates.[[File:Istockphoto-1295483613-612x612.jpg|thumb]]They have become truly remarkable for their '''high resistance''' to extreme environments such as freezing at temperatures close to absolute zero, high temperatures up to 150°C, extreme dehydration, starvation for decades, high levels of radiation and space vacuum, extreme pressures, both high and low... This is made possible by their ability to shut down their organs and stop their metabolism when environmental conditions are not suitable (this is called '''cryptobiosis''') and come back to life when optimal conditions are restored. | ||