First off let’s pretend that I went through a lengthly apology for not posting here in quite a while. Secondly let’s pretend that you have accepted this apology graciously and are just happy to have another ramble by Ryan to read. That out of the way let’s meet todays star attraction…
This is Turritopsis nutricula. A few days ago I attended a conference on stem cell biology and this little gem of a beast cropped up. Before I go into why it is such a remarkable creature I’ll have to share a few facts about jellyfish. Jellyfish belong to the Cnidarian phylum and Cnidarians are the most distantly related group on Earth compared to all other animals. This is because Cnidarians diverged from the rest of us animals over half a billion years ago. Consequently they are quite different; they possess radial symmetry unlike us bilateria, they lack the highly conserved (not to mention ancient) hox genes and rather disturbingly their mouth and anus is the same hole. So what did I find particularly fascinating about this specimen? After all it isn’t very remarkable to look at. In spite of the picture T. nutricula don’t grow beyond half a centimeter and whilst the adults have nearly one hundred tentacles there are far more dangerous jellyfish out there. No the remarkable thing about T. nutricula is that it is biologically immortal.
Yup that’s right, immortal. T. nutricula start off life as larvae that attach to the sea floor and form a polyp, this polyp will begin to asexually produce small sexually mature jellyfish that will bud off of the polyp. Different species of jellyfish have different lifespans (hours-months) but after reproducing most jellyfish die. This is where T. nutricula differs; instead of meekly passing away a T. nutricula will begin to turn from a mature jellyfish back into a polyp! This polyp can then recreate the mature form and the cycle can continue indefinitely, literally rejuvenating itself over and over again.
The reason that this was bought up at the stem cell conference is because of the mechanism by which T. nutricula does this remarkable Benjamin Buttonesque trick. It occurs through a process called transdifferentiation. Cells start life as a stem cell that then undergoes a division forming two cells; one cell identical to the original and one more specialized cell. Transdifferation is the rare process by which specialized cells transform into a different type of specialized cell. This is as strange as brain tissue turning into muscle but this is how T. nutricula cheats death. It starts changing into an odd blob that sinks to the sea floor. This blob then anchors on and forms a polyp again. In reality T. nutricula does die thanks to the hazards of the sea (predation, disease etc) but efforts are now underway to keep them safe in the lab and observe their bizarre life cycle for as long as possible. So who knows? Perhaps future generations of stem cell biologists will be studying the same creatures that are even now being investigated for new insights into stem cell medicines. All I know is that I want one. I mean, who wouldn’t want the one pet that wouldn’t get flushed down the toilet after a few months?