The immortal jellyfish

[Bogdan]

Turritopsis nutricula, the immortal jellyfish, is a hydrozoan whose medusa, or jellyfish, form can revert to the polyp stage after becoming sexually mature. It is the only known case of an 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.

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 indefinitely, effectively rendering the jellyfish biologically immortal, 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. No single specimen has been observed for any extended period, so it is not currently possible 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.

Source

We already know about trees and even other animals that lived hundreds of years (well mostly plants), but this one caught my attention. Apparently after it reaches adult age and reproduces he is able to revelt itself to the 'initial form', imagine an adult human that could revert itself to the embryo (well it's not that easy for mammals, I guess, especially for humans that would have to watch for their children a good part of their life) and restart his life, again.

I want your opinions for this, can we exploit this in the future and if it happens, will it result in anything good?

[nin10mode]

Maybe in like, another 2000 years.

Humans seem like they'd be a lot more difficult. Just look at the size difference between the average toddler and the average adult. It would be impossible for us to revert to a younger form without some loss of cells, and something tells me that would severely damage our bodies initially. The process would take much longer in humans than it would for jellyfish, which means it's very probable that germs and bacteria can enter our reverting bodies and potentially kill us before all our bodily organs completely revert. You'd have to revert in a special kind of room, perhaps with similarities with an ovary if the process would go how I think it would.

Speaking of ovaries, would that mean you can be a virgin more than once? :p

[Newgeneration]

can we exploit this in the future and if it happens, will it result in anything good?

Maybe not soon, or maybe not likely at all, though I've heard there's actually a rare condition that some newborn children have where their growth rate is a fifth of the norm. (link to article on subject, video autoplays, keep that in mind) To be honest, the chances of that creating immortality in humans is much more likely than reverting humans back to their embryo stage, and god forbid if they do, that could be a little creepy to think of someone you know reverting back to being a baby again.

[brandoprojectm]

This post by brandoprojectm was thumbed up by:

Dtroid (September 26th, 2013, 3:42 am)

[Raz]

Living forever can be bad. Overpopulation for example.
I much prefer dying at like..90

[darthbrowser]

The key here is cellular transdifferentiation - the same process which allows stem cells to fulfill numerous needs in humans. Essentially, stem cells are systemic within jellyfish - each cell is totipotent. This is contrasted with most other species, including humans, which feature stem cells spread throughout the body in very limited amounts.

Th article quoted in the OP is, by necessity, incomplete. To achieve its transformation, Turritopsis nutricula stores numerous cell differentiation and growth factors in sacs throughout its body. When its begins the process, the differentiation sacs burst, flooding the jellyfish's body with differentiation factors which trigger the majority of its cells to die, and the rest to convert themselves in embryonic cells.

The mass cell apoptosis allows the jellyfish to decrease in size, while providing ample intracellular resources for the remaining cells in the process. The invertebrate then retracts its muscular hydrostats and umbrella, forming a tight sphere of biomass with the embryonic cells at its center. At this point the sacs containing growth factor burst, releasing the factor and causing the embryonic cells to began mitosis to reform the jellyfish's body, using the surrounding biomass of the old body for resources to do so. At the end of the process, the differentiation and growth factor sacs are reformed, setting the stage for the next event.

This is incompatible for humans for a single, glaring reason - humans are not invertebrates. They cannot collapse themselves into a ball of biomass like Turritopsis nutricula, as the bones are too difficult to break down and reforge. Also, the jellyfish's oceanic environment provides it with the ability to suspend itself at a particular spatial position, and the water pressure helps form its biomass into a sphere. If a land mammal did the same thing, they would essentially turn into a flat puddle of biomass, leaving no room for a core of embryonic cells. Perhaps most importantly, the jellyfish loses all knowledge that is not instinctual during the process - if a mammal underwent the process, its brain would be forced to dissolve, losing all of its memories. The species are not only very different biologically, but also have very different environments.

That is not to say some aspects of Turritopsis nutricula's rebirthing cannot be applied to humans. The most promising idea is the possibility for an animal's cells to all be fully totipotent - which would allow for incredible recovery speeds in cases of physical injury, as well as the possibility to regrow all the most crucial of limbs (i.e., the head). While totipotency would not affect cell specialization (in Turritopsis nutricula, cells differentiate and specialize as usual, they simply retain the ability to re-specialize if a new differentiation factor is applied) and thus the general functioning of the human body, it would nevertheless be very difficult to implement. The genetic modifications would have to involve new instructions for not only cell growth and differentiation, but also the perceived functions of the cells - such as automatic limb regrowth.

A great deal of further research into genetic engineering is required to even consider attempting such a modification on humans.