What creature has no heart and no brain, and is the only known immortal animal?
Turritopsis dohrnii! Otherwise known as the immortal jellyfish.
Working As a Team
All jellyfish lack hearts and brains. Despite this, these creatures have adapted to a variety of environments. They live in saltwater and freshwater, near the surface and throughout the deep ocean, in cold Arctic water and warm tropical waters. The immortal jellyfish resides in both temperate and tropical regions- virtually half of our globe.
Various jellyfish species start as polyps. During this phase, they create colonies by attaching to something stable on the seafloor. Polyp colonies consist of a wide network made up of connections between each polyp. If one polyp has had enough to eat and notices that another polyp is hungry, the nourished polyp will send nutrients via zooplankton and other microscopic ocean animals to ensure its neighbor is well-fed. They likely resonate with the phrase, “All for one, and one for all.”
Polyp colonies can remain stationary for years. Eventually, though, the polyps become jellyfish.
How to Stay Young 101
Although many jellyfish species experience the same growth stages as the immortal jellyfish, other species lack the distinctive ability that has not yet been discovered in any other animal: reversing time.
Living organisms tend to have a linear timeline filled with multiple life stages. The immortal jellyfish can restart this timeline by reverting to polyp form. You read that right. After maturing into a jellyfish and swimming away from the polyp colony, the immortal jellyfish can become a polyp once again and begin a new colony, restarting the life cycle.
This amazing feat is possible due to transdifferentiation. During this process, a mature cell transforms itself into a different type of cell (an ability only seen in stem cells of young organisms). With no limitations to the number of times the jellyfish can undergo this process, this creature can theoretically live forever.
Talk about regeneration!
With Great Power Comes Great… Limitations?
Unfortunately, the immortal jellyfish does not decide when transdifferentiation takes place. Despite the amazing abilities of this creature, the jellyfish depends on a variety of factors to be able to move forward (and backward) in life. From polyp to jellyfish to polyp, the immortal jellyfish relies on its internal state and external environment. For example, the transformation back to polyp form often takes place when the immortal jellyfish feels threatened or has become injured.
In a sense, reverting to its younger self is a defense mechanism. When humans do this, psychologists call it regression. Perhaps we have been trying to imitate the immortal jellyfish all along!