--- title: "Immortal Jellyfish (Turritopsis dohrnii) | AnimalTracks.wiki" description: "A bell up to 3.3 millimetres wide that can turn back into a polyp instead of dying, in the lab at least." image: "https://animaltracks.wiki/images/animals/immortal-jellyfish-1.webp" published: "2026-08-30" updated: "2026-09-29" --- # Immortal Jellyfish (*Turritopsis dohrnii*) > **Status**: Checked against 5 sources, listed under Sources below. > **Tagline**: A bell up to 3.3 millimetres wide that can turn back into a polyp instead of dying, in the lab at least. > **Soundtrack Vibe**: Dream Pop & Shoegaze // M83, "Midnight City" > **Soundtrack Links**: [Spotify](https://open.spotify.com/track/6GyFP1nfCDB8lbD2bG0Hq9) | [YouTube](https://www.youtube.com/watch?v=dX3k_QDnzHE) > **Vibe Match**: Midnight City's looping synth swell, for a medusa that, when old, damaged or starved, can turn into a cyst of poorly differentiated cells and then back into a polyp, the stage medusae bud from. ## Biological Superpowers & Stats - **Taxonomy**: *Turritopsis dohrnii* - **Danger Level**: Low - **Conservation Status**: Not Evaluated ([IUCN Red List](https://www.iucnredlist.org/)) - **Superpower**: Life cycle reversal: a damaged, starved or aging medusa becomes a cyst, then a polyp - **Habitat**: Rocks, docks and hulls as a polyp, open water as a medusa: the Western Mediterranean and Adriatic, plus introduced populations in Florida, Panama and Japan - **Diet**: Zooplankton - **Tags**: cnidarian, ocean, carnivore ## Natural History & Behavior ## Two Bodies, One Animal Unlike almost all animals, including most jellyfish, some cnidarian species can turn a medusa back into a polyp. *Turritopsis dohrnii* is the one the press christened the "immortal jellyfish." It has two body forms. The polyp is a branching colony that sticks to rocks, docks, pilings and ships' hulls. The colony buds off medusae, the jellyfish form, which drift as plankton. An adult medusa is up to 2.7 millimetres tall and 3.3 millimetres wide. The species eats zooplankton, tiny animals adrift in the sea. Medusae have separate sexes. Their eggs and sperm join to make larvae called planulae, which settle and grow into new polyps. It was first described from Naples, Italy, and its polyps are common on rocks in the Western Mediterranean and the Adriatic. ## The Rewind Button > **Life cycle reversal** A senescent (old), weakened or damaged medusa can transform into a cluster of poorly differentiated cells called the cyst stage, and the cyst then metamorphoses back into a polyp. Starved medusae do the same, and a Smithsonian species database says the restart makes each individual "potentially immortal." The switch involves transdifferentiation, in which specialised cells are reprogrammed into other cell types. A 2019 study compared the three stages and found DNA repair genes more active in the cyst than in the polyp or the medusa. The authors say that may be part of how the reset works. ## Immortal, With Fine Print "Immortal" is shorthand. A 2022 genome paper calls *T. dohrnii* immortal because the chance of a sexually mature medusa rejuvenating goes up to 100%, with no apparent limit on the number of cycles for one individual. Another 2022 genome paper counted just two species of hydrozoan jellyfish, *T. dohrnii* and a second, unidentified *Turritopsis*, that had shown repeated reversal in the laboratory. The unidentified one went through as many as 10 reversals in response to severe damage with needles. Names are messy too. Medusae in this genus have been widely labelled *T. nutricula* around the world, and its look-alike species can only be identified by DNA. ## A Quiet Hitchhiker A genetic study found the same species in Florida, Panama and Japan as in Spain and Italy, and called it a human-mediated introduction. Its authors say *Turritopsis* medusae that revert when starved or damaged can easily survive long trips in cargo ships and ballast water. ## Frequently Asked Questions ### Can the immortal jellyfish really live forever? The reversal restarts the life cycle, which researchers say makes each individual potentially immortal. A medusa that is hurt, starved or old can switch back to a polyp, and a 2022 genome study reports no apparent limit to how many times one individual can do it. The repeats have been watched in the laboratory. *(Source: [Pascual-Torner et al. 2022]())* ### How does the immortal jellyfish reverse its life cycle? The medusa shrinks, stops swimming and settles onto the bottom. It turns into a cyst-like stage with a thin outer envelope and no features you could call medusa or polyp. Over the next 24 to 36 hours it develops polyp features, including the structure new polyps arise from. *(Source: [Matsumoto, Piraino & Miglietta 2019]())* ### How big is an adult immortal jellyfish? Tiny. Adult medusae measure up to 3.3 millimetres across, and the polyp colonies grow up to 35 millimetres high. Newly released medusae carry 8 to 12 tentacles, and adults carry 14 to 32, though the adult count differs by place: 8 in Bocas del Toro, Panama, 12 to 24 in Italy and 14 to 24 in Japan. *(Source: [NEMESIS, Smithsonian Environmental Research Center]())* ## Sources 1. [Hasegawa et al. (2022). Genome assembly and transcriptomic analyses of the repeatedly rejuvenating jellyfish Turritopsis dohrnii. DNA Research.]() 2. [Pascual-Torner et al. (2022). Comparative genomics of mortal and immortal cnidarians unveils novel keys behind rejuvenation. Proceedings of the National Academy of Sciences.]() 3. [Matsumoto, Piraino & Miglietta (2019). Transcriptome Characterization of Reverse Development in Turritopsis dohrnii (Hydrozoa, Cnidaria). G3 Genes|Genomes|Genetics.]() 4. [Miglietta & Lessios (2008). A silent invasion. Biological Invasions.]() 5. [Turritopsis dohrnii. NEMESIS, Smithsonian Environmental Research Center.]() *Published August 30, 2026. Last updated September 29, 2026.* ```json { "@context": "https://schema.org", "@graph": [ { "@type": "Article", "@id": "https://animaltracks.wiki/animals/immortal-jellyfish/#article", "isPartOf": { "@id": "https://animaltracks.wiki/#website" }, "headline": "Immortal Jellyfish (Turritopsis dohrnii) | AnimalTracks.wiki", "description": "A bell up to 3.3 millimetres wide that can turn back into a polyp instead of dying, in the lab at least.", "image": [ "https://animaltracks.wiki/images/animals/immortal-jellyfish-1.webp" ], "datePublished": "2026-08-30", "dateModified": "2026-09-29", "author": [ { "@type": "Organization", "name": "AnimalTracks.wiki Editorial Team", "url": "https://animaltracks.wiki" } ], "publisher": { "@type": "Organization", "@id": "https://animaltracks.wiki/#organization", "name": "AnimalTracks.wiki", "url": "https://animaltracks.wiki", "logo": { "@type": "ImageObject", "url": "https://animaltracks.wiki/icon-512.png" } }, "mainEntityOfPage": "https://animaltracks.wiki/animals/immortal-jellyfish/", "citation": [ { "@type": "ScholarlyArticle", "name": "Genome assembly and transcriptomic analyses of the repeatedly rejuvenating jellyfish Turritopsis dohrnii", "url": "https://doi.org/10.1093/dnares/dsac047", "author": "Hasegawa et al.", "datePublished": "2022", "isPartOf": { "@type": "Periodical", "name": "DNA Research" }, "identifier": "doi:10.1093/dnares/dsac047" }, { "@type": "ScholarlyArticle", "name": "Comparative genomics of mortal and immortal cnidarians unveils novel keys behind rejuvenation", "url": "https://doi.org/10.1073/pnas.2118763119", "author": "Pascual-Torner et al.", "datePublished": "2022", "isPartOf": { "@type": "Periodical", "name": "Proceedings of the National Academy of Sciences" }, "identifier": "doi:10.1073/pnas.2118763119" }, { "@type": "ScholarlyArticle", "name": "Transcriptome Characterization of Reverse Development in Turritopsis dohrnii (Hydrozoa, Cnidaria)", "url": "https://doi.org/10.1534/g3.119.400487", "author": "Matsumoto, Piraino & Miglietta", "datePublished": "2019", "isPartOf": { "@type": "Periodical", "name": "G3 Genes|Genomes|Genetics" }, "identifier": "doi:10.1534/g3.119.400487" }, { "@type": "ScholarlyArticle", "name": "A silent invasion", "url": "https://doi.org/10.1007/s10530-008-9296-0", "author": "Miglietta & Lessios", "datePublished": "2008", "isPartOf": { "@type": "Periodical", "name": "Biological Invasions" }, "identifier": "doi:10.1007/s10530-008-9296-0" }, { "@type": "CreativeWork", "name": "Turritopsis dohrnii", "url": "https://invasions.si.edu/nemesis/species_summary/-502", "publisher": { "@type": "Organization", "name": "NEMESIS, Smithsonian Environmental Research Center" } } ], "about": { "@type": "Taxon", "name": "Immortal Jellyfish", "scientificName": "Turritopsis dohrnii", "description": "Life cycle reversal: a damaged, starved or aging medusa becomes a cyst, then a polyp" } }, { "@type": "FAQPage", "@id": "https://animaltracks.wiki/animals/immortal-jellyfish/#faq", "mainEntity": [ { "@type": "Question", "name": "Can the immortal jellyfish really live forever?", "acceptedAnswer": { "@type": "Answer", "text": "The reversal restarts the life cycle, which researchers say makes each individual potentially immortal. A medusa that is hurt, starved or old can switch back to a polyp, and a 2022 genome study reports no apparent limit to how many times one individual can do it. The repeats have been watched in the laboratory.", "citation": { "@type": "ScholarlyArticle", "name": "Comparative genomics of mortal and immortal cnidarians unveils novel keys behind rejuvenation", "url": "https://doi.org/10.1073/pnas.2118763119", "author": "Pascual-Torner et al.", "datePublished": "2022", "isPartOf": { "@type": "Periodical", "name": "Proceedings of the National Academy of Sciences" }, "identifier": "doi:10.1073/pnas.2118763119" } } }, { "@type": "Question", "name": "How does the immortal jellyfish reverse its life cycle?", "acceptedAnswer": { "@type": "Answer", "text": "The medusa shrinks, stops swimming and settles onto the bottom. It turns into a cyst-like stage with a thin outer envelope and no features you could call medusa or polyp. Over the next 24 to 36 hours it develops polyp features, including the structure new polyps arise from.", "citation": { "@type": "ScholarlyArticle", "name": "Transcriptome Characterization of Reverse Development in Turritopsis dohrnii (Hydrozoa, Cnidaria)", "url": "https://doi.org/10.1534/g3.119.400487", "author": "Matsumoto, Piraino & Miglietta", "datePublished": "2019", "isPartOf": { "@type": "Periodical", "name": "G3 Genes|Genomes|Genetics" }, "identifier": "doi:10.1534/g3.119.400487" } } }, { "@type": "Question", "name": "How big is an adult immortal jellyfish?", "acceptedAnswer": { "@type": "Answer", "text": "Tiny. Adult medusae measure up to 3.3 millimetres across, and the polyp colonies grow up to 35 millimetres high. Newly released medusae carry 8 to 12 tentacles, and adults carry 14 to 32, though the adult count differs by place: 8 in Bocas del Toro, Panama, 12 to 24 in Italy and 14 to 24 in Japan.", "citation": { "@type": "CreativeWork", "name": "Turritopsis dohrnii", "url": "https://invasions.si.edu/nemesis/species_summary/-502", "publisher": { "@type": "Organization", "name": "NEMESIS, Smithsonian Environmental Research Center" } } } } ] }, { "@type": "MusicRecording", "name": "Midnight City", "byArtist": { "@type": "MusicGroup", "name": "M83" }, "genre": "Dream Pop & Shoegaze", "url": "https://open.spotify.com/track/6GyFP1nfCDB8lbD2bG0Hq9" } ] } ```