[ExI] potentially "immortal" jellyfish species

[Robert Bradbury]

On Sun, Feb 1, 2009 at 3:10 AM, John Grigg <possiblepaths2050 at gmail.com>wrote:

> This small jellyfish is extremely talented...
>
> "...when starvation, physical damage, or other crises arise, "instead of
> sure death, *[Turritopsis]* transforms all of its existing cells into a
> younger state," said study author Maria Pia Miglietta, a researcher at
> Pennsylvania State University..., The jellyfish's cells are often completely
> transformed in the process. Muscle cells can become nerve cells or even
> sperm or eggs."
>
>
> http://news.nationalgeographic.com/news/2009/01/090130-immortal-jellyfish-swarm.html
>

John, as I have discussed on the GRG list this is a situation where the term
"immortal" should not be used.  This is a case where the cells of an
organism may "dedifferentiate" (i.e. return to an embryonic or
quasi-embryonic state).  As it turns out scientists at NYU have determined
that plant cells may either dedifferentiate or transdifferentiate to create
cells which rejuvinate the plant without the requirement for stem cells.
Certain reptiles and amphibians may have similar capabilities (as evidenced
by their ability to regrow limbs).

For the term "immortal" to be used you need to verify that 100% of the cells
are capable of performing this dedifferentiation and redifferentiation
activity.  That *HAS NOT BEEN DONE*.  Thus only the cells which happen to
have maintained relatively perfect genomes (which is a fraction of the total
cells) can be capable of pulling off this hat trick.  So the question I ask
(given that you are citing this) is "Would you want a brain with only 30% of
its original cells? (Assuming an arbitrary number that survive the
dedifferentiation and redifferentiation process.).    I have lines I draw in
the sand with respect to saying "that is me" and "that is not me".  You may
or may not feel the same.

Robert
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