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title: "What the sources say about the Immortal Jellyfish | AnimalTracks.wiki"
description: "41 claims from the Immortal Jellyfish profile, each beside the words of the source that backs it."
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# What the sources say about the Immortal Jellyfish (*Turritopsis dohrnii*)

> 41 claims from the Immortal Jellyfish profile, each beside the words of the source that backs it. A "..." marks a cut in a quote and [brackets] an insertion.

Profile: [Immortal Jellyfish](https://animaltracks.wiki/animals/immortal-jellyfish/)

## Hasegawa et al. (2022). Genome assembly and transcriptomic analyses of the repeatedly rejuvenating jellyfish Turritopsis dohrnii. DNA Research.

https://doi.org/10.1093/dnares/dsac047

| The page says | The source says |
| :--- | :--- |
| Unlike almost all animals, including most jellyfish, some cnidarian species can turn a medusa back into a polyp. | Unlike almost all multicellular animals, including most jellyfish species, some cnidarian species show life cycle reversion, 1–8 in which mature and young medusae transform directly into an earlier developmental stage namely, the polyp stage (note: footnote numbers inside quote; verify may need ... cut) |
| 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. | Only two hydromedusan species, Turritopsis dohrnii and T . sp., have exhibited experimental multiple-repeat life cycle reversion in the laboratory (note: Hasegawa et al. 2022 (DNA Research). Hydromedusan = hydrozoan jellyfish; T. sp. = unidentified species. Past tense: a count as of 2022; the 2024 Mnemiopsis report is a ctenophore, outside the hydromedusan scope) |
| The unidentified one went through as many as 10 reversals in response to severe damage with needles. | Turritopsis sp. showed as many as 10 repeated cycles of rejuvenation in response to severe mechanical damage with needles. |
| The repeats have been watched in the laboratory. | have exhibited experimental multiple-repeat life cycle reversion in the laboratory |

## Pascual-Torner et al. (2022). Comparative genomics of mortal and immortal cnidarians unveils novel keys behind rejuvenation. Proceedings of the National Academy of Sciences.

https://doi.org/10.1073/pnas.2118763119

| The page says | The source says |
| :--- | :--- |
| 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. | we define T. dohrnii as “immortal” because the probability of sexually mature medusae to rejuvenate goes up to 100%, with no apparent limit in the number of ontogeny reversal cycles for a given individual (note: 2022 is the reference's year field (Pascual-Torner 2022)) |
| 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. | with no apparent limit in the number of ontogeny reversal cycles for a given individual (note: 2022 is the reference's year field (Pascual-Torner 2022)) |

## Matsumoto, Piraino & Miglietta (2019). Transcriptome Characterization of Reverse Development in Turritopsis dohrnii (Hydrozoa, Cnidaria). G3 Genes|Genomes|Genetics.

https://doi.org/10.1534/g3.119.400487

| The page says | The source says |
| :--- | :--- |
| that can turn back into a polyp instead of dying, in the lab at least | Medusae of Turritopsis dohrnii undergo reverse development in response to physical damage, adverse environmental conditions, or aging. (note: tagline; 'in the lab at least' hedges: the repeats were seen in the laboratory (hasegawa-2022 claim below)) |
| Life cycle reversal: a damaged, starved or aging medusa becomes a cyst, then a polyp | Senescent, weakened or damaged medusae transform into a cluster of poorly differentiated cells (known as the cyst stage), which metamorphose back into a preceding life cycle stage, the polyp. (note: stats.superpower; starved is NEMESIS (claim below)) |
| 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. | Senescent, weakened or damaged medusae transform into a cluster of poorly differentiated cells (known as the cyst stage), which metamorphose back into a preceding life cycle stage, the polyp. |
| A 2019 study compared the three stages and found DNA repair genes more active in the cyst than in the polyp or the medusa. | in the Cyst stage, the category ‘DNA repair (GO:0006281)’ was also found to be over-expressed in all three comparative analyses (note: 2019 is the reference's year field; the three analyses were Cyst vs Polyp, Cyst vs Medusa, Cyst vs Polyp+Medusa; polyps and medusae came from Otranto, Italy and cysts from Bocas del Toro, Panama, so no place is named) |
| The authors say that may be part of how the reset works. | Biological processes that occur at the cyst stage such as telomerase activity, regulation of transposable elements and DNA repair systems, and suppression of cell signaling pathways, mitotic cell division and cellular differentiation and development may be involved in T. dohrnii ’s reverse development and transdifferentiation. |
| The medusa shrinks, stops swimming and settles onto the bottom. | During its reverse development, medusae shrink and lose their swimming competence, settle onto the substrate |
| It turns into a cyst-like stage with a thin outer envelope and no features you could call medusa or polyp. | transform into a cyst-like stage characterized by a thin chitinous external envelope with no recognizable morphological features that can be ascribed to either medusa or polyp |
| Over the next 24 to 36 hours it develops polyp features, including the structure new polyps arise from. | In the following 24-36 hr, the cyst develops polyp-typical features, such as the stolonal hydrorhiza, where new polyps will arise from |
| The switch involves transdifferentiation, in which specialised cells are reprogrammed into other cell types. | the ontogeny reversal of T. dohrnii involves cell transdifferentiation, a reprogramming of structural and functional commitment and gene expression of well-differentiated, somatic cells into other cell types (note: well-differentiated = specialised) |
| a medusa that, when old, damaged or starved, can turn into a cyst of poorly differentiated cells and then back into a polyp | Senescent, weakened or damaged medusae transform into a cluster of poorly differentiated cells (known as the cyst stage), which metamorphose back into a preceding life cycle stage, the polyp. (note: vibe.reason, task #969) |

## Miglietta & Lessios (2008). A silent invasion. Biological Invasions.

https://doi.org/10.1007/s10530-008-9296-0

| The page says | The source says |
| :--- | :--- |
| A genetic study found the same species in Florida, Panama and Japan as in Spain and Italy | a clade of the mitochondrial 16S gene in Turritopsis which contains individuals collected from Japan, the Pacific and Atlantic coasts of Panama, Florida, Spain, and Italy |
| and called it a human-mediated introduction. | Here we identify a human mediated, worldwide introduction of the hydrozoan species Turritopsis dohrnii. |
| Its authors say Turritopsis medusae that revert when starved or damaged can easily survive long trips in cargo ships and ballast water. | Medusae of Turritopsis, however, when starved or damaged, are able to revert their life cycle, going back to the polyp stage through a process called transdifferentiation. They can thus easily survive through long journeys in cargo ships and ballast waters. |

## Turritopsis dohrnii. NEMESIS, Smithsonian Environmental Research Center.

https://invasions.si.edu/nemesis/species_summary/-502

| The page says | The source says |
| :--- | :--- |
| A bell up to 3.3 millimetres wide | The adult medusae are up to 2.7 mm in height and 3.3 mm in diameter, with 14-32 tentacles. |
| Rocks, docks and hulls as a polyp | The hydroid stage of this species can be found attached to rocks, docks, pilings and ships' hulls. (note: stats.habitat; hydroid = polyp stage) |
| open water as a medusa | The colonies grow medusa buds which release planktonic medusae. (note: stats.habitat) |
| the Western Mediterranean and Adriatic, plus introduced populations in Florida, Panama and Japan | is a common hydroid on rocky substrates in the Western Mediterranean and Adriatic ... Introduced populations are known from the Indian River Lagoon, Florida; both the Caribbean and Pacific coasts of Panama; and Japan. (note: stats.habitat) |
| Zooplankton | Food: Zooplankton (note: stats.diet; GBIF has no IUCN category for this name (prefetch: no assessment), so conservationStatus stays Not Evaluated; no status claim on the page) |
| The polyp is a branching colony that sticks to rocks, docks, pilings and ships' hulls. | The hydroid stage of this species can be found attached to rocks, docks, pilings and ships' hulls. |
| The colony buds off medusae, the jellyfish form, which drift as plankton. | The colonies grow medusa buds which release planktonic medusae. |
| An adult medusa is up to 2.7 millimetres tall and 3.3 millimetres wide | The adult medusae are up to 2.7 mm in height and 3.3 mm in diameter, with 14-32 tentacles. |
| The species eats zooplankton | Food: Zooplankton |
| It was first described from Naples, Italy, and its polyps are common on rocks in the Western Mediterranean and the Adriatic. | It was first described from Naples, Italy, and is a common hydroid on rocky substrates in the Western Mediterranean and Adriatic (note: hydroid = polyp; rocky substrates = rocks) |
| Starved medusae do the same, and a Smithsonian species database says the restart makes each individual "potentially immortal." | starved medusae can settle to become an undifferentiated cyst, which grows into a new polyp, restartimg the life cycle. This process of transdifferentiation makes each individual organism potentially immortal |
| Medusae in this genus have been widely labelled T. nutricula around the world, and its look-alike species can only be identified by DNA. | Medusae of the genus Turritopsis have been widely identified as T. nutricula McCrady, 1857 (described from Charleston, South Carolina) around the world ... Identification of the cryptic species of Turritopsis is only possible by molecular means (note: cryptic species = look-alike species; molecular means = DNA (paraphrase)) |
| The reversal restarts the life cycle, which researchers say makes each individual potentially immortal. | This process of transdifferentiation restarts the life cycle, and makes each individual organism potentially immortal |
| the polyp colonies grow up to 35 millimetres high. | much-branched, multiple-stemmed colonies up to 35 mm high |
| Newly released medusae carry 8 to 12 tentacles, and adults carry 14 to 32 | Newly released medusae have 8-12 tentacles, and a conical manubrium ... The adult medusae are up to 2.7 mm in height and 3.3 mm in diameter, with 14-32 tentacles. (note: tentacle counts are not hedged; 'up to' in the quote belongs to the size sentence) |
| 8 in Bocas del Toro, Panama, 12 to 24 in Italy and 14 to 24 in Japan | Numbers of tentacles in adult medusae vary regionally with: 8 in Bocas del Toro, Panama; 12-24 in Italy; and 14-24 in Japan |
| Turritopsis dohrnii is the one the press christened the "immortal jellyfish." | Turritopsis dohrnii has been christened 'Immortal Jellyfish' in the popular press |
| It has two body forms. | Turritopsis dohrnii is a hydrozoan with both a polyp and medusa stage. |
| Medusae have separate sexes. Their eggs and sperm join to make larvae called planulae, which settle and grow into new polyps. | The medusae have separate sexes, and release gametes which fuse to form planulae, which settle to form hydroids. (note: gametes = eggs and sperm; hydroids = polyps; 'larvae' is the definition of planula) |
| Adult medusae measure up to 3.3 millimetres across | The adult medusae are up to 2.7 mm in height and 3.3 mm in diameter (note: faq 3) |
| starved | starved medusae can settle to become an undifferentiated cyst, which grows into a new polyp (note: vibe.reason, task #969) |
| the stage medusae bud from | The colonies grow medusa buds which release planktonic medusae. (note: vibe.reason, task #969) |