It can be quite puzzling how humans have come so far from being mere hunter/gatherers to forming civilized and scientifically advanced societies. However, one subject that continues to puzzle us is mortality. Despite being able to cure the deadliest of diseases, we have yet to find the secret to not just elongating our lifespans, but rather, living forever. That is why it can be very important to acknowledge a remarkable creature that is living under the sea: the jellyfish Turritopsis dohrnii. The Turritopsis dohrnii is a jellyfish that can live forever because of a neat biological trick that Mother Nature has played on it.
What is the Turritopsis dohrnii?
This quirky jellyfish is a fish that can transform its old cells into young cells by will alone. By young, though, we don’t mean just teenagers. Our special jellyfish can make its cells so young that it becomes a mere polyp again, the jellyfish version of a caterpillar!
The life cycle of jellyfishes
To understand how T. dohrnii works, we need to know the life cycle of a typical jellyfish first. Jellyfishes begin their life as a planula larva, which is essentially an egg cell that has been fertilized by a jellyfish sperm cell. Jellyfish mothers eject these out into the water, forming clusters of planula larvae floating around in the water. Some of these eventually get eaten by predators. Those lucky few that don’t meet the same fate as their siblings land on coral beds and form polyps, which can look a bit like predatory plants. These polyps don’t move around, but they can capture plankton for their nutrition.
When polyps grow, they form lots of buds. These buds are stacked on top of each other, and each of them becomes an ephyra larva which eventually become the kinds of jellyfish that we know and love. Biologists call this the medusa stage. Medusae normally die off when they become too old, unless they are eaten by predators.
Now unlike most jellyfishes, our T. dohrnii can turn itself back into a special polyp when it starves or sustains severe cellular damage. This kind of polyp is really special because some of the medusa’s organs, like the reproductive ones, are left intact and untransformed.
dohrnii does a thing that biologists like to call totipotency. This is when a mature cell could become a young cell again which could turn into any kind of cell that the body needs. Most polyp cells in normal polyps are pluripotent, which means that they can turn into any other kind of cell. When totipotent cells become pluripotent, then that is how our immortal jellyfish get eternal youth. The scientific word for this is called senescence.
Applications for human senescence
The cells of T. dohrnii are a really important key for biologists, geneticists, and pharmacologists to use so we could learn how to make ourselves young again. There is a problem, however: it is hard to keep these jellyfish in captivity! There is one scientist who is known to have kept live T. dohrnii colonies in his laboratory for a long time. His name is Shin Kubota and he works for Tokyo University. He kept these for 2 years, feeding them and observing as he studied how they lived. He even sometimes sang songs to them in their tanks! All the way from 2009 to 2010, he recorded when they turned back into polyps and then transformed into medusae again.
As of now, scientists all over the world are studying which genes are responsible in controlling their ability to become young again. At the rate and direction that the research around the T. dohrnii continues, there’s a huge possibility that the concepts of immortality and eternal youth that you’ve only seen in fiction will actually become a reality in the future!