Immortal Jellyfish (Turritopsis dohrnii)

Immortal Jellyfish overview

The immortal jellyfish is a tiny hydrozoan, smaller than a pea, that is famous for being able to reverse its own life cycle. Like other hydrozoans it has a bottom-living polyp stage that buds off free-swimming medusae. Uniquely, when a medusa of this species is starved, injured or simply grows old, it can shrink into a blob of tissue, settle on the bottom and turn back into a young polyp colony, which then buds off new, genetically identical medusae. In that narrow sense it is 'biologically immortal'. In the sea, most individuals are simply eaten or die of disease like any other plankton.

How Long Do Immortal Jellyfish Live?

There is no fixed lifespan for the immortal jellyfish: a single medusa normally lasts only weeks to a few months, but it can revert to a polyp and start its life cycle again. Medusae mature in about 18–30 days, depending on temperature. In a Japanese laboratory one lineage was taken through ten rejuvenation cycles in two years. 'Immortal' does not mean unkillable; in the wild most are eaten or die of disease.

How Long Is an Immortal Jellyfish?

A fully grown immortal jellyfish is only about 4.5 mm (0.18 in) across, roughly as tall as it is wide and smaller than a pea. Newly released medusae are about 1 mm in diameter with just eight tentacles, while adults carry 80–90 tentacles around the rim of the bell.

What Do Immortal Jellyfish Eat?

Immortal jellyfish are carnivores that eat tiny zooplankton, including copepods, larvae and fish eggs. They catch prey with stinging cells on their tentacles and digest it in a bright red stomach that is visible through the transparent bell. In laboratories they are fed newly hatched brine shrimp.

Diet type: carnivore. Tiny zooplankton such as copepods, larvae and fish eggs, caught with stinging tentacles; laboratory colonies are usually raised on newly hatched brine shrimp.

Where Do Immortal Jellyfish Live?

Immortal jellyfish live in coastal seawater in temperate and tropical regions. The species was first described from the Mediterranean and is well studied in Japan, and genetically matching animals have since been found off Panama, Florida, Spain and elsewhere, most likely carried around the world in the ballast water of ships.

Are Immortal Jellyfish Endangered?

The immortal jellyfish has not been evaluated for the IUCN Red List, and nothing suggests it is threatened. It is spreading rather than declining: researchers have described its quiet, worldwide expansion through shipping as a 'silent invasion', because the animal is so small and inconspicuous that it goes unnoticed.

Not Evaluated

Immortal Jellyfish fun facts

• When stressed, an immortal jellyfish medusa absorbs its own bell and tentacles, sinks to the bottom as a cyst-like blob and within days grows into a new polyp.
• The reversal involves transdifferentiation, in which specialized cells change directly into other cell types, a process of great interest to researchers studying aging and regeneration.
• Its ability to reverse its life cycle was first reported by scientists in the 1990s, working with specimens from the Mediterranean.
• Medusae produced after a reversal are genetic copies of the original, so what persists is arguably the genetic individual rather than one continuous body.
• Its genome was sequenced and compared with a close, non-rejuvenating relative in a study published in 2022, highlighting extra copies of genes linked to DNA repair.

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Immortal Jellyfish FAQ

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