Tardigrade
Tardigrades ('water bears') are microscopic, segmented animals.[1] They live in water. They are members of the tactopod phylum Tardigrada, part of the superphylum Ecdysozoa. They are also known as water bears or moss piglets.[2][3]
Tardigrades | |
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Milnesium tardigradum, a eutardigrade | |
Echiniscus succineus, a heterotardigrade | |
Scientific classification | |
Unrecognized taxon (fix): | Tardigrades |
Classes | |
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Tardigrades were first described in 1773.[4] Their name means "slow stepper". There are more than 1000 different species of tardigrade.[5]
Tardigrades have a cylindrical shape with four segments, each with two legs. Each leg has little claws.[5] 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.[4] Tardigrades feed on plant cells by penetrating the cell wall and eating what is inside. Some tardigrades are carnivores.[6][5]
Tardigrades are eutelic: all adult tardigrades of the same species have the same number of cells. Some species have as many as 40,000 cells in each adult, while others have far fewer.[7][8]
Tardigrades can be found in many habitats: in moss,[6] freshwater,[6] the Himalayas,[4] and the ocean.[4] They are one of the few animals that can be found on the highest mountains and the deepest seas.[4] About 83% of the known species live on land, the other 17% live in water.[5]
Survivability
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.[9][10] This meant living in a vacuum with severe radiation.[11][12][13]
Tardigrades can survive more than ten years without water.[14] Tardigrades can survive extreme temperatures. They can live for a few hours in temperatures close to absolute zero[6] and above boiling point.[14] They can survive a few minutes in temperatures as high as 151 °C (304 °F).[15][16] Some tardigrades can survive being frozen for over 30 years.[17]
Tardigrades can also survive radiation at hundreds of times a level that would be deadly to humans.[18][19] They can also survive in toxic environments[20] and during impact events.[21]
In 2019, a lander with Tardigrades on board crashed on the moon. It is believed that the Tardigrades survived and could live for a few years on the moon.[22][23]
The tardigrades slow their metabolism to survive these environments.[24] Rotifers have a similar agility to survive.
Tardigrade Media
SEM image of Hypsibius dujardini
Video of tardigrade under the microscope
Living tardigrades moving around
Hypsibius dujardini imaged with a scanning electron microscope
Tardigrade (unknown species, ventral view) imaged using scanning electron microscopy
References
- ↑ 1.0 1.1 Neuman, Yair (October 2006). "Cryptobiosis: A new theoretical perspective". Progress in Biophysics and Molecular Biology. Elsevier. 92 (2): 258–267. doi:10.1016/j.pbiomolbio.2005.11.001. PMID 16380155.
- ↑ Miller, William (2017-02-06). "Tardigrades". American Scientist. Archived from the original on 2018-04-14. Retrieved 2018-04-13.
- ↑ Simon, Matt (21 March 2014). "Absurd Creature of the Week: the incredible Ccritter that's tough enough to survive in the vacuum of space". Wired. https://www.wired.com/wiredscience/2014/03/absurd-creature-week-water-bear/. Retrieved 2014-03-21.
- ↑ 4.0 4.1 4.2 4.3 4.4 Riffenburgh, Beau (2007). Encyclopedia of the Antarctic. Vol. 1 (illustrated ed.). CRC Press. p. 983. ISBN 978-0-415-97024-2.
- ↑ 5.0 5.1 5.2 5.3 Margulis, Lynn; Schwartz, Karlene V. (1998). Five kingdoms: an illustrated guide to the phyla of life on earth (illustrated ed.). Elsevier. p. 324. ISBN 978-0-7167-3027-9.
- ↑ 6.0 6.1 6.2 6.3 "Tardigrade (animal)". Encyclopædia Britannica. Archived from the original on 2011-01-23. Retrieved 2011-01-02.
- ↑ Seki, Kunihiro; Toyoshima, Masato 1998. Preserving tardigrades under pressure. Nature 395 (6705): 853–854. Preserving tardigrades under pressure | Nature Archived 2021-02-14 at the Wayback Machine
- ↑ Kinchin, Ian M. 1994. The biology of tardigrades. Ashgate Publishing.
- ↑ Jönsso, K. Ingema; et al. (2008). "Tardigrades survive exposure to space in low Earth orbit". Current Biology. 18 (17): R729–R731. doi:10.1016/j.cub.2008.06.048. PMID 18786368. S2CID 8566993. Archived from the original on 9 April 2011. Retrieved 1 January 2011.
- ↑ Whalen, Joann K.; Sampedro, Luis (2010). Soil Ecology and Management (illustrated ed.). CABI. p. 73. ISBN 978-1-84593-563-4.
- ↑ "Creature survives naked in space". Space.com. 8 September 2008. Archived from the original on 2018-10-11. Retrieved 2011-12-22.
- ↑ Jönsson, K. Ingemar; Rabbow, Elke; Schill, Ralph O; Harms-Ringdahl, Mats; Rettberg, Petra (2008). "Tardigrades survive exposure to space in low Earth orbit". Current Biology. 18 (17): R729–R731. doi:10.1016/j.cub.2008.06.048. PMID 18786368. S2CID 8566993.
- ↑ Courtland, Rachel (8 September 2008). "'Water bears' are first animal to survive space vacuum". New Scientist. https://www.newscientist.com/article/dn14690-water-bears-are-first-animal-to-survive-space-vacuum.html. Retrieved 2011-05-22.
- ↑ 14.0 14.1 Grimaldi, David; Engel, Michael S. (2005). Michael S. Engel (ed.). Evolution of the insects. Cambridge Evolution Series (illustrated, reprint ed.). Cambridge University Press. p. 97. ISBN 978-0-521-82149-0.
- ↑ Horikawa, Daiki D (2012). "Survival of Tardigrades in Extreme Environments: A Model Animal for Astrobiology". In Altenbach, Alexander V.; Bernhard, Joan M.; Seckbach, Joseph (eds.). Anoxia. Cellular Origin: life in extreme habitats and astrobiology. Vol. 21. pp. 205–17. doi:10.1007/978-94-007-1896-8_12. ISBN 978-94-007-1895-1.
- ↑ (in en-US) Extreme animals - Astrobiology Magazine. 2002-09-01. https://www.astrobio.net/extreme-life/extreme-animals/. Retrieved 2018-02-12.
- ↑ BBC News: News from elewhere. Japan: 'Water bear' reproduces after 30 years on ice - BBC News Archived 2021-02-23 at the Wayback Machine
- ↑ "Radiation tolerance in the tardigrade Milnesium tardigradum" (PDF).[dead link]
- ↑ Horikawa, Daiki D.; Sakashita, Tetsuya; Katagiri, Chihiro; Watanabe, Masahiko; Kikawada, Takahiro; Nakahara, Yuichi; Hamada, Nobuyuki; Wada, Seiichi; Funayama, Tomoo (2006-01-01). "Radiation tolerance in the tardigrade Milnesium tardigradum". International Journal of Radiation Biology. 82 (12): 843–848. doi:10.1080/09553000600972956. ISSN 0955-3002. PMID 17178624. S2CID 25354328. Archived from the original on 2021-10-31. Retrieved 2021-10-31.
- ↑ Jönsson, K. Ingemar; Bertolani, Roberto (2001). "Facts and fiction about long-term survival in tardigrades". Journal of Zoology. 255 (1): 121–3. doi:10.1017/S0952836901001169. Archived from the original on 2021-10-31. Retrieved 2021-10-31.
- ↑ Sloan, David; Alves Batista, Rafael; Loeb, Abraham (2017). "The Resilience of Life to Astrophysical Events". Scientific Reports. 7 (1): 5419. arXiv:1707.04253. Bibcode:2017NatSR...7.5419S. doi:10.1038/s41598-017-05796-x. PMC 5511186. PMID 28710420.
- ↑ Sample, Ian (6 August 2019). Tardigrades may have survived spacecraft crashing on moon. https://www.theguardian.com/science/2019/aug/06/tardigrades-may-have-survived-spacecraft-crashing-on-moon. Retrieved 7 August 2019.
- ↑ Resnick, Brian (6 August 2019). Tardigrades, the toughest animals on Earth, have crash-landed on the moon. https://www.vox.com/science-and-health/2019/8/6/20756844/tardigrade-moon-beresheet-arch-mission. Retrieved 7 August 2019.
- ↑ "The almost indestructible water bear". Awake!. 88 (3): 30. March 2007. ISSN 0005-237X. Archived from the original on 7 August 2019. Retrieved 7 August 2019.