Animals

How long do they live? That's a great big "we don't know." Jellyfish begin as a small polyp stage and then mature into a medusa stage (See figure 1). Well, Turritopsis dohrnii go through the same stages, but when they are stressed they can revert back into their polyp form until conditions are good and then they can return to their medusa form. They can do this indefinitely for all we know, which pretty much makes them the only known immortal animal on our planet [1].

Where are they found? Many sources mention that they are found all throughout tropical ocean waters, but they are mainly found in the Mediterranean Sea and near Japan [2]. Turritopsis dohrnii was formerly mislabeled as Turritopsis nutricula leading to possible misconceptions of their actual habitat.

What do they eat? They eat fish eggs, plankton and tiny mollusks depending on where they are.

What do they look like? They're tiny at only about 4.5 mm in size. They are mostly studied through a microscope, but they are large enough to be seen with the naked eye.

How do they reproduce? Like us, they have eggs and sperm. Unlike us, they release those eggs and sperm into the ocean during spawning.

How do scientists know how old they are? Each time the jellyfish regenerate themselves, they go through something called transdifferentiation, which means a cell changes into a different cell without the need for stem cells [3]. Kind of like if a butterfly turned back into a caterpillar very quickly and then back into a butterfly, but completely regenerated as if it were brand new. Therefore scientists can assume that these are the only known biologically immortal creatures. They're not immune to being ate by everything else in the ocean, though.

So what are we lacking? How are they doing this transdifferentiation trick? There's also no information identifying reproductive senescence in this species. No nuclear genome data of Turritopsis dohrnii has been uploaded to the  NCBI (National Center for Biotechnology Information) .

And extra weirdness: Here's an informative video about Shin Kubota, the only scientist that successfully cultures these immortal jellyfish in his lab. And here's a video of the same scientist with a jellyfish on his head singing about the immortal jellyfish because he can.

Please contact me if you have information regarding how I can pull off the same magic trick as these little jellyfish.

1. Ma, Hongbao, and Yan Yang. "Turritopsis nutricula." Nature and Science 8.2 (2010): 15-20.
2. Fofonoff PW, Ruiz GM, Steves B, & Carlton JT. 2003. National Exotic Marine and Estuarine Species Information System. http://invasions.si.edu/nemesis/.Access Date: 26-Aug -2016
3. Piraino, Stefano, et al. "Reversing the life cycle: medusae transforming into polyps and cell transdifferentiation in Turritopsis nutricula (Cnidaria, Hydrozoa)." The Biological Bulletin 190.3 (1996): 302-312.