At the very root of our evolutionary tree there exist an immense variety of simple organisms. The phylum cnidaria alone contains over 10, 000 species, mostly anemones, corals and jellyfish. Recently a particular species of jellyfish has received a fair amount of attention due to some new and exciting observations. Swimming amongst the swarm of growing media headlines, this magnificent and gelatinous organism could potentially unlock some mysteries about life on our planet.
Turritopsis dohrnii (formerly known as Turritopsis nutricula) is one species of jellyfish, only 5mm in diameter and found worldwide, with a very exceptional quality: it is biologically immortal. How does this work? Most jellyfish die soon after they reproduce, however this mature jellyfish instead reverts itself back to a new immature polyp stage (baby jellyfish). It
does this through transdifferentiation, the process of switching one differentiated cell type into another cell type with a different form and function. Transdifferentiation is rare; when it occurs it is usually limited to one part of the organism, not the whole. Yet this fascinating jellyfish has managed to incorporate this process into its very life cycle. Turritopsis nutricula is the only known organism capable of returning to a stage of sexual immaturity after reproducing, to mature again, reproduce, and return to immaturity again and again.
Shin Kubota, an associate professor at the University of Kyoto, has been studying the life cycle of the Turritopsis dohrnii for many years and has found that 100% of the time when the jellyfish experience illness, trauma or are simply too old, they form themselves back into young polyps and once again reign in their gelatinous youth. This makes it almost impossible to know how old they really are. So in theory, we know that as long as its nerve centre remains intact, this jellyfish could sustain its life indefinitely. What could this mean for us? If we could gain a complete understanding of their regeneration cycle, perhaps we could one day learn to regenerate our own cells in the hope of extending our time on this planet. This is the dream Kubota works for.
As stem-cell research appears at the forefront of medical research for organ reproduction and cancer treatments, there is a real possibility that these new findings hold a key to unlocking some very big mysteries. This particular research also eliminates the ethical and moral dilemmas that arise when working with embryonic stem cells. But if given the opportunity, would we really choose to live longer? Extend our life spans past 100, 200, 300 or more years? And which people would have the privilege of doing so? What impacts could this have on the future of food or pollution? So many questions, both ethical and philosophical arise. Perhaps abilities such as rejuvenation are for now, better left to the simple, aquatic organisms, who have managed to go about their business uninterrupted by humans for over 500 million years.
Hongbao Ma, The Nature of Time and Space. Nature and Science. 2003; 1(1): 1 – 10.
Hongbao Ma, Yan Yang. Turritopsis nutricula. Nature and Science. 2010; 8(2): 15 – 20.
Kubota Shin. Repeating rejuvenation in Turritopsis, an immortal hydrozoan (Cnidaria, Hydrozoa. Biogeography. 2011. 13: 101 – 103.
The Jellyfish That Holds a Key to Immortality. (video file). Published on May 6, 2014. Motherboard. Retrieved from: https://www.youtube.com/watch?v=eMOkXkw5TKc. Accessed: Apr 26, 2015.
Image 1: Chris Williamson, “Moon Jellyfish”, Flickr, July 2009, under Attribution licence
Image 2: Peter Schuchert, The Hydrozoa Directory
This article first appeared in the Australia Times Science Magazine.