You’re growing old, fragile and, perhaps worst of all, wrinkly. If only you could go back to being a baby, and grow up all over again. This might sound like a curious fantasy but for one member of the animal kingdom it’s just part of life.
Turritopsis nutricula is the Immortal Jellyfish. As a member of the Hydrozoa class, it has two stages within its life cycle: the polypois and medusoid stages. In polyp form these jellyfish are grouped together in colonies, with several polyps connected in a tree-like manner by a series of tubes called hydrocauli. These polyps are little more than mouths, terrifying mouths covered in vicious, stinging tentacles. It’s certainly comforting to know they’re less than one millimetre tall. The medusa stage is the larger, sexually mature form sizing up to a slightly underwhelming 4.5 mm. It’s a more conventional jellyfish shape with around 100 stinging tentacles trailing below a bright red stomach.
Unlike all other Hydrozoans, the transformation from polyp to medusa isn’t a one way street for Turritapsis. When conditions are unfavourable the jellyfish is able to use cells from certain tissues to revert back, with its bell and tentacles deteriorating in exchange for hydrocauli. This ability to reverse metamorphose means that the jellyfish is biologically immortal. With this extraordinary trait it isn’t much of a surprise to hear that this species is quickly spreading across the oceans. According to Dr Maria Miglietta of the Smithsonian Tropical Marine Institute we’re seeing ‘a worldwide silent invasion’. Let’s hope they don’t get much bigger.
Did you know Synapse featured The Immortal Jellyfish in issue 3 of our print magazine? It made it onto the front cover!