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Turritopsis nutricula

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posted on Aug, 29 2008 @ 01:25 PM
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Turritopsis nutricula is a hydrozoan with a life cycle in which it reverts back to the polyp stage after becoming sexually mature. It is the only known case of a metazoan (animal) capable of reverting completely to a sexually immature, colonial stage after having reached sexual maturity as a solitary stage . It does this through the cell development process of transdifferentiation. Theoretically, this cycle can repeat indefinitely, rendering it effectively immortal.


en.wikipedia.org...

[edit on 29-8-2008 by CzErased]

Mod Edit: Added Ex tags

[edit on 29-8-2008 by Gemwolf]




posted on Aug, 29 2008 @ 01:34 PM
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The Immortal Life Cycle of Turritopsis

While colonial animals can have their immortality, solitary individuals are doomed to die. Hydrozoan cnidarians usually have a complex life cycle, wherein a colonial stage leads to the sexually mature, solitary, adult stage. Eggs and sperm from solitary, sexual, adult medusa (jellyfish) develop into an embryo and planula larva, and they then form the colonial polyp stage. Medusae are formed asexually from polyps. These medusae have a limited lifespan and die shortly after releasing their gametes

The hydrozoan Turritopsis nutricula has evolved a remarkable variation on this theme, and in so doing appears to have achieved immortality. The solitary medusa of this species can revert to its polyp stage after becoming sexually mature (Bavestrello et al., 1992; Piraino et al., 1996). In the laboratory, 100% of these medusae regularly undergo this change. Thus, it is possible that organismic death does not occur in this species!

How does Turritopsis accomplish this feat? It can do this because it can alter the differentiated state of a cell, transforming it into another cell type. Such a phenomenon is called transdifferentiation, and it is usually seen only when parts of an organ regenerate. However, it appears to occur normally in the Turritopsis life cycle (Figure 2). In this transdifferentiation process, the medusa is transformed into the stolons and polyps of a hydroid colony. First, the umbrella everts and the tentacles and mesoglea (the middle layer) are resorbed. The everted medusa attach to the substrate by the end that had been at the opposite end of the umbrella, and spawning occurs shortly thereafter. The cnidarian then secretes a perisarc (stolon covering) and stolons. Two days after the stolons are first seen, polyps differentiate. These polyps feed on zooplankton and soon are budding off new medusae.


The cells that accomplish the building of a new stolon are probably those of the exumbrella (the upper portion of the jellyfish dome). Transformation into stolons only occurs in fragments that contain tissues of the exumbrella and the ring canals, and the exumbrella tissue is the only tissue of the medusa that can transdifferentiate into the perisarc-secreting epidermal tissue of the stolons (Piraino et al., 1996). (The endoderm of the ring canals probably becomes the endoderm of the stolon and polyps.) It is not known whether the sensory cells, myoepithelial cells, and cnidocytes are derived from the exumbrella or the endodermal component.

Turritopsis nutricula is the first case in which a metazoan is capable of reverting completely to a sexually immature, colonial stage after having reached sexual maturity as a solitary stage. Thus, it appears that it has cheated death and is a potentially immortal, solitary metazoan.



8e.devbio.com...

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[edit on 29-8-2008 by Gemwolf]



posted on Aug, 29 2008 @ 03:46 PM
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It can cheat death, so long as it continues to mate on the next cycle.

That really is intriguing.
The old Buddhist(?) saying "Sex is the key to immortality" really rings true in this species case... in a literal sense this time.

I can see why this form of cycle might be beneficial to the species. Those which are deemed appealing to the species get to continue pro-creating indefinitely. Those not, well... lol, they die like the rest.

Fascinating method of species survival.



 
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