Examine individual changes

'{{italictitle}} {{Taxobox | name = Immortal jellyfish | image = | image_caption = ''Turritopsis nutricula'' SEXY SEXY SEXY MONKEY | status = Not Evaluated | status_system = | status_ref = | regnum = [[Animal]]ia | phylum = [[Cnidaria]] | classis = [[Hydrozoa]] | ordo = [[Anthomedusae]] | familia = [[Oceanidae]] | genus = '''''Turritopsis''''' | species = '''''T. nutricula''''' | binomial = ''Turritopsis nutricula'' | binomial_authority = [[McCrady]], 1857<ref>[http://www.eol.org/pages/1015922 Turritopsis nutricula McCrady 1857] - Encyclopedia of Life</ref> }} '''''Turritopsis nutricula''''' , the potentially '''immortal jellyfish''', is a [[hydrozoa]]n whose medusa, or [[jellyfish]], form can revert to the [[polyp]] stage after becoming [[sexual reproduction|sexually mature]]. It is the only known case of a [[animal|metazoan]] capable of reverting completely to a sexually immature, colonial stage after having reached sexual maturity as a solitary stage.<ref>{{cite journal|last=Bavestrello|first=Giorgio|coauthors=Christian Sommer and Michele Sarà|year=1992|title=Bi-directional conversion in Turritopsis nutricula (Hydrozoa)|journal=Scientia Marina|volume=56|issue=2-3|pages=137–140}}</ref><ref name="piraino-96">{{cite journal|last=Piraino|first=Stefano|coauthors=F. Boero, B. Aeschbach, V. Schmid|year=1996|title=Reversing the life cycle: medusae transforming into polyps and cell transdifferentiation in Turritopsis nutricula (Cnidaria, Hydrozoa)|journal=Biological Bulletin|volume=190|issue=3|pages=302–312|doi=10.2307/1543022|url=http://jstor.org/stable/1543022|publisher=Biological Bulletin, Vol. 190, No. 3}}</ref> It does this through the cell development process of [[transdifferentiation]]. Cell transdifferentiation is when the jellyfish "alters the differentiated state of the cell and transforms it into a new cell." In this process the medusa of the immortal jellyfish is transformed into the polyps of a new polyp colony. First, the umbrella reverts itself and then the tentacles and mesoglea get resorbed. The reverted medusa then attaches itself to the substrate by the end that had been at the opposite end of the umbrella and starts giving rise to new polyps to form the new colony. Theoretically, this process can go on infinitely, effectively rendering the jellyfish [[Biological immortality|biologically immortal]],<ref name="piraino-96"/><ref name="CheatingDeath">{{cite web|url=http://8e.devbio.com/preview_article.php?ch=2&id=6|title=Cheating Death: The Immortal Life Cycle of Turritopsis|last=Gilbert|first=Scott F.|year=2006|accessdate=2009-03-22}}</ref> although in nature, most ''Turritopsis'', like other medusae, are likely to succumb to predation or disease in the [[plankton]] stage, without reverting to the polyp form.<ref name="National Geographic News">{{cite web |title="Immortal" Jellyfish Swarm World's Oceans |author=Ker Than |url=http://news.nationalgeographic.com/news/2009/01/090130-immortal-jellyfish-swarm.html |date=January 29, 2009 |publisher=[[National Geographic News]] |accessdate=2010-06-16 }}</ref>. No single specimen has been observed for any extended period, so it is impossible to estimate the age of an individual, and so even if this species has the potential for immortality, there is no laboratory evidence of many generations surviving from any individual. ==Description== The medusa of ''Turritopsis nutricula'' is bell-shaped, with a maximum diameter of about {{convert|4.5|mm|in}} and is about as tall as it is wide.<ref>{{cite journal|last=Kramp|first=P.L.|title=Synopsis of the medusae of the world.|journal=Journal of the Marine Biological Association of the United Kingdom|volume=40|pages=1–469}}</ref><ref name="TimesOnline26012009" /> The jelly in the walls of the bell is uniformly thin, except for some thickening at the apex. The relatively large stomach is bright red and has a cruciform shape in cross section. Young specimens 1 mm in diameter have only eight tentacles evenly spaced out along the edge, while adult specimens have 80-90 tentacles. The medusa (jellyfish) is free-living in the plankton. ''Turritopsis nutricula'' also has a bottom-living polyp form, or hydroid, which consists of stolons that run along the substrate, and upright branches with feeding polyps that can produce medusa buds.<ref>{{cite book|last=Fraser|first=C. McLean|title=Hydroids of the Pacific Coast of Canada and the United States|publisher=University of Toronto Press|year=1937|pages=201 plus 44 plates}}</ref> These buds develop over a few days into tiny 1 mm medusae, which are liberated and swim free from the parent hydroid colony. Images of both the medusa and polyp of the closely related species ''Turritopsis rubra'' from New Zealand can be found online.<ref name="schuchert-10">{{cite web|url=http://www.ville-ge.ch/mhng/hydrozoa/antho/turritopsis-rubra.htm|title=Turritopsis rubra|last=Schuchert|first=Peter|accessdate=23 January 2010}}</ref> Until a recent genetic study, it was thought that ''Turritopsis rubra'' and ''Turritopsis nutricula'' were the same. It is not known whether or not ''T. rubra'' medusae can also transform back into polyps. ==Distribution and range== ''Turritopsis'' is believed to have originated in the [[Caribbean]] but has spread all over the world, and has speciated into several populations that are difficult to distinguish morphologically, but whose species distinctions have recently been verified by a study and comparison of mitochondrial ribosomal gene sequences.<ref name="telegraph-09">{{cite web|url=http://www.telegraph.co.uk/earth/wildlife/4357829/Immortal-jellyfish-swarming-across-the-world.html|title='Immortal' jellyfish swarming across the world |date=January 27, 2009|publisher=[[Telegraph Media Group]]|accessdate=2010-06-16}}</ref><ref>{{cite journal|last=Miglietta|first=M. P.|coauthors=S. Piraino, S. Kubota, P. Schuchert|year=2006|title=Species in the genus Turritopsis (Cnidaria, Hydrozoa): a molecular evaluation|journal=Journal of Zoological Systematics and Evolutionary Research|volume=45|issue=1|pages=11–19|doi=10.1111/j.1439-0469.2006.00379.x}}</ref> ''Turritopsis'' are found in temperate to tropical regions in all of the world's oceans.<ref name="TimesOnline26012009">{{cite web|url=http://www.timesonline.co.uk/tol/news/uk/science/article5594539.ece|title=Turritopsis nutricula: the world's only 'immortal' creature|last=Mintowt-Czyz |first=Lech|date=26 January 2009|publisher=[[Times Online]]|accessdate=2009-03-22}}</ref> ''Turritopsis'' is believed to be spreading across the world as ships are [[Ballast water discharge and the environment|discharging]] [[ballast water]] in ports.<ref name="TimesOnline26012009" /> Since the species is immortal, the number of individuals could be spiking. "We are looking at a worldwide silent invasion" said [[Smithsonian Tropical Research Institute|Smithsonian Tropical Marine Institute]] scientist Dr. Maria Pia Miglietta.<ref name="telegraph-09"/> ==Life cycle== The eggs develop in gonads of female medusae, which are located in the walls of the manubrium (stomach). Mature eggs are presumably spawned and fertilized in the sea by sperm produced and released by male medusae, as is the case for most hydromedusae, although the related species ''Turritopsis rubra'' seems to retain fertilized eggs until the planula stage<ref name="schuchert-10"/>. Fertilized eggs develop into [[planula]] larvae, which settle onto the sea floor (or even the rich marine communities that live on floating docks), and develop into polyp colonies ([[hydroids]]). The hydroids bud new jellyfishes, which are released at about 1 mm in size and then grow and feed in the plankton, becoming sexually mature after a few weeks (the exact duration depends on the ocean temperature; at {{convert|20|C|F}} it is 25 to 30 days and at {{convert|22|C|F}} it is 18 to 22 days).<ref name="piraino-96"/> ===Biological immortality=== Most jellyfish species have a relatively fixed life span, which varies by species from hours to many months (long-lived mature jellyfish spawn every day or night [the time is also rather fixed and species-specific]<ref>{{cite journal|last=Mills|first=C. E.|year=1983|title=Vertical migration and diel activity patterns of hydromedusae: studies in a large tank.|journal=Journal of Plankton Research|volume=5|pages=619–635|doi=10.1093/plankt/5.5.619}}</ref>). The medusa of ''Turritopsis nutricula'' is the only form known to have developed the ability to return to a polyp state, by a specific transformation process that requires the presence of certain cell types (tissue from both the jellyfish bell surface and the circulatory canal system). Careful laboratory experiments have revealed that all stages of the medusae, from newly released to fully mature individuals, can transform back into polyps.<ref name="piraino-96"/> The transforming [[medusae|medusa]] is characterized first by deterioration of the bell and tentacles, with subsequent growth of a perisarc sheet (see [[hydroid]]) and stolons, and finally feeding polyps. Polyps further multiply by growing additional stolons, branches and then polyps, to form colonial [[hydroids]]. This ability to reverse the life cycle (in response to adverse conditions) is probably unique in the animal kingdom, and allows the jellyfish to bypass death, rendering ''Turritopsis nutricula'' potentially [[biological immortality|biologically immortal]]. Studies in the laboratory showed that 100% of specimens could revert to the polyp stage, but so far the process has not been observed in nature, in part because the process is quite rapid and field observations at the right moment in time are unlikely.<ref name="piraino-96" /> In spite of this remarkable ability, most ''Turritopsis'' medusae are likely to fall victim to the general hazards of life as plankton, including being eaten by other animals, or succumbing to disease. ==See also== *[[List of long-living organisms]] *[[Biological immortality]] *''[[Hydra (genus)|Hydra]]''&nbsp;– another kind of cnidarian that is claimed to be immortal ==References== {{reflist|2}} ==Further reading== * {{Cite journal | last1=Piraino | first1=S. | last2=Boero | first2=F. | last3=Aeschbach | first3=B. | last4=Schmid | first4=V. | title=Reversing the Life Cycle: Medusae Transforming into Polyps and Cell Transdifferentiation in Turritopsis nutricula (Cnidaria, Hydrozoa) | journal=The Biological Bulletin | volume=190 | issue=3 | year=1996 | url=http://www.biolbull.org/cgi/reprint/190/3/302 | doi=10.2307/1543022 | pages=302 | jstor=1543022 | publisher=Biological Bulletin, Vol. 190, No. 3 | postscript=<!--None-->}} ==External links== * [http://8e.devbio.com/preview_article.php?ch=2&id=6 Cheating Death: The Immortal Life Cycle of ''Turritopsis''] * [http://www.ncbi.nlm.nih.gov/pubmed/19000774?log$=activity Telomerase activity is not related to life history stage in the jellyfish Cassiopea sp.] *{{eol|1015922}} * [http://scienceray.com/biology/scientists-are-close-to-finding-a-way-to-be-immortal/ ] {{wikispecies|Clavidae}} {{Longevity}} [[Category:Hydrozoa]] [[Category:Immortality]] [[ca:Turritopsis nutricula]] [[cs:Turritopsis nutricula]] [[de:Turritopsis nutricula]] [[es:Turritopsis nutricula]] [[fr:Turritopsis nutricula]] [[ko:작은보호탑해파리]] [[it:Turritopsis nutricula]] [[he:Turritopsis nutricula]] [[hu:Turritopsis nutricula]] [[mk:Turritopsis nutricula]] [[nl:Turritopsis nutricula]] [[ja:ベニクラゲ]] [[no:Turritopsis nutricula]] [[pl:Turritopsis nutricula]] [[pt:Turritopsis nutricula]] [[ro:Turritopsis nutricula]] [[sr:Turritopsis nutricula]] [[fi:Turritopsis nutricula]] [[zh:灯塔水母]]'