Tardigrade

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Tardigrada
The tardigrade Hypsibius dujardini
Conservation status
Scientific classification
Kingdom: Animalia
Superphylum: Ecdysozoa
Phylum: Tardigrada

Tardigrades ('water bears') form the phylum Tardigrada, part of the superphylum Ecdysozoa. They are microscopic, water-dwelling, segmented animals.[1]

Tardigrades were first described in 1773.[2] There are more than 1000 different species of tardigrade.[3]

Tardigrades have a cylindrical shape with four segments, each with two legs. Each of their limbs have little claws.[3] The biggest adults may reach a body length of 1.2 mm, the smallest below 0.1 mm. Freshly hatched larvae may be smaller than 0.05 mm.[2] Tardigrades feed on plant cells by penetrating the cell wall and eating what is inside. Some tardigrades are carnivores.[4][3]

Tardigrades can be found in many habitats: in moss,[4] freshwater,[4] the Himalayas,[2] and the ocean.[2] They are one of the few animals that can be found on the highest mountains and the deepest seas.[2] About 83 percent of the species live on land, the other 17 percent live in water.[3]

Tardigrades are able to live in environments that would kill most animals.[1] In 2007, scientists discovered that some tardigrades were able to survive 10 days in outer space.[5][6] Tardigrades can survive more than ten years without water.[7] Tardigrates can survive a few hours in temperatures close to absolute zero[4] and above boiling point.[7]

References[change | edit source]

  1. 1.0 1.1 Neuman, Yair (October 2006). "Cryptobiosis: A new theoretical perspective". Progress in Biophysics and Molecular Biology (Elsevier) 92 (2).
  2. 2.0 2.1 2.2 2.3 2.4 Riffenburgh, Beau (2007). Encyclopedia of the Antarctic. Encyclopedia of the Antarctic. 1 (illustrated ed.). CRC Press. pp. 983. ISBN 0415970245.
  3. 3.0 3.1 3.2 3.3 Margulis, Lynn; Schwartz, Karlene V. (1998). Five kingdoms: an illustrated guide to the phyla of life on earth (illustrated ed.). Elsevier. pp. 324. ISBN 0716730278.
  4. 4.0 4.1 4.2 4.3 "Tardigrade (animal)". Encyclopædia Britannica. http://www.britannica.com/EBchecked/topic/583460/tardigrade. Retrieved 2011-01-02.
  5. Jönsson, K. Ingema; Rabbow, Elke; Schill, Ralph O.; Harms-Ringdahl, Mats; Rettberg, Petra (9 September 2008). "Tardigrades survive exposure to space in low Earth orbit". Current Biology (Elsevier Ltd) 18 (17). ISSN R729-R731. http://www.cell.com/current-biology/abstract/S0960-9822%2808%2900805-1. Retrieved 1 January 2011.
  6. Whalen, Joann K.; Sampedro, Luis (2010). Soil Ecology and Management (illustrated ed.). CABI. pp. 73. ISBN 1845935632.
  7. 7.0 7.1 Grimaldi, David A.; Engel, Michael S. (2005). Michael S. Engel. ed. Evolution of the insects. Cambridge Evolution Series (illustrated, reprint ed.). Cambridge University Press. pp. 97. ISBN 0521821495.
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