So occassionally things will just catch my attention.... Immortal hydrozoa happens to be one of those things.
Turritopsis nutricula, now otherwise known as IMMORTAL jellyfish has a similar life cycle to other jellyfish, egg, larva, polyp (Which are alot like coral...in fact coral and jellyfish are related) and then finally the medusae stage (the actual jellyfish we're used to thinking of). This in itself isn't particularly astounding, most jellyfish do this the same way, with more or less steps depending on the species. The medusae stage typically has a fixed lifetime that can range from a few hours to a few months.
What makes this one special is the fact that they can revert back to a previous life stage, reverting from it's adult stage back into the polyp stage, effectively staving off death and resting, preparing to breed again. This process is accomplished by a process called transdifferentiation which alters the differentiated state of the cell and transforms it into a new cell. In this process the medusae of the immortal jellyfish is transformed into the polyps of a new polyp colony. The jellyfish reabsorbs its tentacles and umbrella in this process, repurposing the cells to form the polyp colony. This process, in theory can go on indefinitely...making it effectively immortal, avoiding the pre-determined death of the medusae stage.
There are alot of ramifications of this discovery... and how it affects us as humans. It has been thought for a long time that telomeres (the repeating sequences of DNA at the end of chromosomes) are directly linked to aging (they do shorten as we age). However in the case of the jellyfish, there appears to be no link to telomere length and the lifestage of the jellyfish... While we are significantly different animals, DNA tends to operate similarly in most eukaryotes and casts doubt on previous hypothesises on the link between telomere's and age.
A more pragmatic, and disturbing, ramification is that without proper predation, these creatures can very easily take over the oceans...and that seems to be what they are doing. The immortal jellyfish can now be found across the world in virtually every ocean. Given that overfishing has made several fish likely to go extinct within my lifetime... with their natural predators gone the immortal jellyfish could take over entirely
I personally would like to welcome our future immortal overlords with open arms...tentacles... Or something like that
Thanks for reading,