Although I don’t keep jellyfish in any of my aquariums (jellyfish can’t typically live in a home hobbyist’s aquarium), I’ve been reading a lot about them in the news. I haven’t made an aquablog post in a while – and this article in The Telegraph about “immortal” jellyfish swarming the world’s oceans really caught my attention.
Jellyfish are Cnidarians, members of the phylum that also includes corals and anemones. These “immortal” jellyfish are hydrozoans, and as such, they start life as little polyp colonies attached to the seafloor. Once a polyp grows to reach a certain stage, it “hatches” a jellyfish (this is also known as “the medusa stage”), which then floats freely in the ocean. Soon, the jellyfish becomes sexually mature and gets together with others to produce larva that will develop into new polyp colonies. After reproducing, most jellyfish die, completing the circle of life…
But that’s where T. nutricula is different! This jellyfish is biologically immortal. Once it becomes sexually mature and reproduces, unlike all the other jellyfish (and every other animal we know about), T. nutricula actually reverts to its polyp stage. It literally grows young again — from an adult jellyfish back to a baby polyp form, and starts its life anew.
While there are obvious practical implications in figuring out just how these jellyfish manage to reverse their aging processes, there are also obvious problems with animals that reproduce but don’t die. Get to work scientists!