--- title: "Tardigrade (Water Bear) (Hypsibius exemplaris) | AnimalTracks.wiki" description: "Eight-legged micro-survivor that meets a dose of gamma rays by rapidly switching on many of its own DNA-repair genes." image: "https://animaltracks.wiki/images/animals/tardigrade-1.webp" published: "2026-08-31" updated: "2026-09-28" --- # Tardigrade (Water Bear) (*Hypsibius exemplaris*) > **Status**: Checked against 7 sources, listed under Sources below. > **Tagline**: Eight-legged micro-survivor that meets a dose of gamma rays by rapidly switching on many of its own DNA-repair genes. > **Soundtrack Vibe**: IDM & Glitch Ambient Synthesis // Aphex Twin, "Windowlicker" > **Soundtrack Links**: [Spotify](https://open.spotify.com/track/409z4jUHpq7eIkg3N3FzZh) | [YouTube](https://www.youtube.com/watch?v=iZ8sZXFN6jc) > **Vibe Match**: Glitch built from chopped and re-spliced sound, for an animal whose DNA is damaged by gamma rays and then repaired: it answers gamma-ray damage by rapidly switching on many DNA-repair genes. ## Biological Superpowers & Stats - **Taxonomy**: *Hypsibius exemplaris* - **Danger Level**: Low - **Conservation Status**: Not Evaluated ([IUCN Red List](https://www.iucnredlist.org/)) - **Superpower**: Dries into a dormant "tun" in which its cells and mitochondria shrink, and answers gamma-ray damage by rapidly switching on many DNA-repair genes. - **Habitat**: Limnoterrestrial (freshwater and land), and best known from a strain kept in many laboratories throughout the world (the wider tardigrade phylum also includes marine species). - **Diet**: In lab culture, the green alga Chlorella vulgaris. - **Tags**: invertebrate, super-tough, extreme-survivor ## Natural History & Behavior ## Not the Tardigrade You Think It Is Tardigrades, also called water bears or moss piglets, have four body segments that each carry two legs. Across the phylum, tardigrades typically run about 0.1 to 1 millimeter long, and in one lab study active *H. exemplaris* measured about 164 micrometers. A commercially sold strain kept in many laboratories throughout the world was assumed to be *Hypsibius dujardini*. When researchers redescribed the real *H. dujardini* from DNA markers and detailed anatomy in 2018, that lab strain turned out to represent "in fact, a new species": *Hypsibius exemplaris*, the animal on this page. ## Shutting Down to Survive Land-dwelling tardigrades need a thin film of water to stay active. Without it, *H. exemplaris* contracts into a compact ball called a tun, the shape tardigrades form to reduce their body surface area and rate of evaporation. In one study, tuns dried for six days measured about 101 micrometers, and the cells and mitochondria inside had shrunk too. Unlike its relative *Ramazzottius varieornatus*, which tolerates rapid desiccation, *H. exemplaris* enters that dormant state only "after extensive pre-exposure to drying conditions." A 2017 genome study dried it slowly, at 85% relative humidity for 48 hours, and counted a batch as successfully dormant when more than 90% of the animals recovered after rehydration. Disordered proteins found only in tardigrades play an essential role in the shutdown. In the lab, one of this species' proteins, CAHS-8, formed long fibres and finally a gel as it grew more concentrated, and soluble proteins caught in the gel's cavities kept their functional form. ## Radiation, Up to a Thousand Times Over Tardigrades can survive doses of ionizing radiation up to about 1,000 times the lethal dose for humans. *H. exemplaris* isn't immune: gamma rays still damage its DNA. What's different is the comeback: the damage is repaired. > **Its own genes come to the rescue** Irradiation rapidly switches on many DNA-repair genes in *H. exemplaris*, pushing some repair transcripts to among the most abundant in the animal. At least one of those genes is important to radiation tolerance in the living animal. A second defense may sit in the nucleus. Dsup, a damage-suppressor protein first found in *R. varieornatus*, has a counterpart in *H. exemplaris*. In lab tests that version also binds to nucleosomes in chromatin, the structure DNA is packaged into, and protects DNA from hydroxyl radicals, which ionizing radiation generates in cells. ## Built for the Lab Lab colonies of *H. exemplaris* are fed the green alga *Chlorella vulgaris*. The species has a generation time under two weeks at room temperature, stocks can be frozen and revived, and its body and embryos are optically clear. Its genome has been sequenced, and researchers have built techniques for it that include microinjection and RNA interference. A 2018 review describes it as an emerging model system, used to study how animal form evolves and how biological materials survive extreme environments. ## Frequently Asked Questions ### Why is this species called Hypsibius exemplaris and not Hypsibius dujardini? Because it turned out not to be dujardini. The strain sold commercially and kept in many labs worldwide had been assumed to be H. dujardini, but a 2018 study that redescribed the real H. dujardini, using DNA markers alongside detailed anatomy, showed the lab strain was a separate species. It was named Hypsibius exemplaris. *(Source: [Gąsiorek et al. 2018]())* ### How does a tardigrade survive being completely dried out? It contracts into a tun. In one study, active Hypsibius exemplaris measured about 164 micrometers and tuns dried for six days about 101, and the cells and mitochondria inside had shrunk too. The researchers read the shrunken mitochondria as a sign that metabolism in a tun is minimal, with limited breathing. *(Source: [Richaud et al. 2020]())* ### How much radiation can tardigrades survive? As a group, up to about 1,000 times the dose of ionizing radiation that would kill a person. Hypsibius exemplaris still takes DNA damage from gamma rays. It survives by fixing it, and in lab tests boosting some of its repair genes in bacteria was enough to raise the bacteria's radiation tolerance. *(Source: [Clark-Hachtel et al. 2024]())* ### What can a dried-out tardigrade survive? In the dried, dormant state, tardigrades resist heat, cold, vacuum, pressure, radiation and chemical treatments, and they have been found to survive exposure to the vacuum and radiation of outer space. Add water and the animal can be rehydrated to an active form. *(Source: [Chavez et al. 2019]())* ## Sources 1. [Gąsiorek et al. (2018). An integrative redescription of Hypsibius dujardini (Doyère, 1840), the nominal taxon for Hypsibioidea (Tardigrada: Eutardigrada). Zootaxa.]() 2. [Chavez et al. (2019). The tardigrade damage suppressor protein binds to nucleosomes and protects DNA from hydroxyl radicals. eLife.]() 3. [Yoshida et al. (2017). Comparative genomics of the tardigrades Hypsibius dujardini and Ramazzottius varieornatus. PLOS Biology.]() 4. [Richaud et al. (2020). Ultrastructural analysis of the dehydrated tardigrade Hypsibius exemplaris unveils an anhydrobiotic-specific architecture. Scientific Reports.]() 5. [Clark-Hachtel et al. (2024). The tardigrade Hypsibius exemplaris dramatically upregulates DNA repair pathway genes in response to ionizing radiation. Current Biology.]() 6. [Malki et al. (2021). Intrinsically Disordered Tardigrade Proteins Self-Assemble into Fibrous Gels in Response to Environmental Stress. Angewandte Chemie International Edition.]() 7. [Goldstein (2018). The Emergence of the Tardigrade Hypsibius exemplaris as a Model System. Cold Spring Harbor Protocols.]() *Published August 31, 2026. Last updated September 28, 2026.* ```json { "@context": "https://schema.org", "@graph": [ { "@type": "Article", "@id": "https://animaltracks.wiki/animals/tardigrade/#article", "isPartOf": { "@id": "https://animaltracks.wiki/#website" }, "headline": "Tardigrade (Water Bear) (Hypsibius exemplaris) | AnimalTracks.wiki", "description": "Eight-legged micro-survivor that meets a dose of gamma rays by rapidly switching on many of its own DNA-repair genes.", "image": [ "https://animaltracks.wiki/images/animals/tardigrade-1.webp" ], "datePublished": "2026-08-31", "dateModified": "2026-09-28", "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/tardigrade/", "citation": [ { "@type": "ScholarlyArticle", "name": "An integrative redescription of Hypsibius dujardini (Doyère, 1840), the nominal taxon for Hypsibioidea (Tardigrada: Eutardigrada)", "url": "https://doi.org/10.11646/zootaxa.4415.1.2", "author": "Gąsiorek et al.", "datePublished": "2018", "isPartOf": { "@type": "Periodical", "name": "Zootaxa" }, "identifier": "doi:10.11646/zootaxa.4415.1.2" }, { "@type": "ScholarlyArticle", "name": "The tardigrade damage suppressor protein binds to nucleosomes and protects DNA from hydroxyl radicals", "url": "https://doi.org/10.7554/elife.47682", "author": "Chavez et al.", "datePublished": "2019", "isPartOf": { "@type": "Periodical", "name": "eLife" }, "identifier": "doi:10.7554/elife.47682" }, { "@type": "ScholarlyArticle", "name": "Comparative genomics of the tardigrades Hypsibius dujardini and Ramazzottius varieornatus", "url": "https://doi.org/10.1371/journal.pbio.2002266", "author": "Yoshida et al.", "datePublished": "2017", "isPartOf": { "@type": "Periodical", "name": "PLOS Biology" }, "identifier": "doi:10.1371/journal.pbio.2002266" }, { "@type": "ScholarlyArticle", "name": "Ultrastructural analysis of the dehydrated tardigrade Hypsibius exemplaris unveils an anhydrobiotic-specific architecture", "url": "https://doi.org/10.1038/s41598-020-61165-1", "author": "Richaud et al.", "datePublished": "2020", "isPartOf": { "@type": "Periodical", "name": "Scientific Reports" }, "identifier": "doi:10.1038/s41598-020-61165-1" }, { "@type": "ScholarlyArticle", "name": "The tardigrade Hypsibius exemplaris dramatically upregulates DNA repair pathway genes in response to ionizing radiation", "url": "https://doi.org/10.1016/j.cub.2024.03.019", "author": "Clark-Hachtel et al.", "datePublished": "2024", "isPartOf": { "@type": "Periodical", "name": "Current Biology" }, "identifier": "doi:10.1016/j.cub.2024.03.019" }, { "@type": "ScholarlyArticle", "name": "Intrinsically Disordered Tardigrade Proteins Self-Assemble into Fibrous Gels in Response to Environmental Stress", "url": "https://doi.org/10.1002/anie.202109961", "author": "Malki et al.", "datePublished": "2021", "isPartOf": { "@type": "Periodical", "name": "Angewandte Chemie International Edition" }, "identifier": "doi:10.1002/anie.202109961" }, { "@type": "ScholarlyArticle", "name": "The Emergence of the Tardigrade Hypsibius exemplaris as a Model System", "url": "https://doi.org/10.1101/pdb.emo102301", "author": "Goldstein", "datePublished": "2018", "isPartOf": { "@type": "Periodical", "name": "Cold Spring Harbor Protocols" }, "identifier": "doi:10.1101/pdb.emo102301" } ], "about": { "@type": "Taxon", "name": "Tardigrade (Water Bear)", "scientificName": "Hypsibius exemplaris", "description": "Dries into a dormant \"tun\" in which its cells and mitochondria shrink, and answers gamma-ray damage by rapidly switching on many DNA-repair genes." } }, { "@type": "FAQPage", "@id": "https://animaltracks.wiki/animals/tardigrade/#faq", "mainEntity": [ { "@type": "Question", "name": "Why is this species called Hypsibius exemplaris and not Hypsibius dujardini?", "acceptedAnswer": { "@type": "Answer", "text": "Because it turned out not to be dujardini. The strain sold commercially and kept in many labs worldwide had been assumed to be H. dujardini, but a 2018 study that redescribed the real H. dujardini, using DNA markers alongside detailed anatomy, showed the lab strain was a separate species. It was named Hypsibius exemplaris.", "citation": { "@type": "ScholarlyArticle", "name": "An integrative redescription of Hypsibius dujardini (Doyère, 1840), the nominal taxon for Hypsibioidea (Tardigrada: Eutardigrada)", "url": "https://doi.org/10.11646/zootaxa.4415.1.2", "author": "Gąsiorek et al.", "datePublished": "2018", "isPartOf": { "@type": "Periodical", "name": "Zootaxa" }, "identifier": "doi:10.11646/zootaxa.4415.1.2" } } }, { "@type": "Question", "name": "How does a tardigrade survive being completely dried out?", "acceptedAnswer": { "@type": "Answer", "text": "It contracts into a tun. In one study, active Hypsibius exemplaris measured about 164 micrometers and tuns dried for six days about 101, and the cells and mitochondria inside had shrunk too. The researchers read the shrunken mitochondria as a sign that metabolism in a tun is minimal, with limited breathing.", "citation": { "@type": "ScholarlyArticle", "name": "Ultrastructural analysis of the dehydrated tardigrade Hypsibius exemplaris unveils an anhydrobiotic-specific architecture", "url": "https://doi.org/10.1038/s41598-020-61165-1", "author": "Richaud et al.", "datePublished": "2020", "isPartOf": { "@type": "Periodical", "name": "Scientific Reports" }, "identifier": "doi:10.1038/s41598-020-61165-1" } } }, { "@type": "Question", "name": "How much radiation can tardigrades survive?", "acceptedAnswer": { "@type": "Answer", "text": "As a group, up to about 1,000 times the dose of ionizing radiation that would kill a person. Hypsibius exemplaris still takes DNA damage from gamma rays. It survives by fixing it, and in lab tests boosting some of its repair genes in bacteria was enough to raise the bacteria's radiation tolerance.", "citation": { "@type": "ScholarlyArticle", "name": "The tardigrade Hypsibius exemplaris dramatically upregulates DNA repair pathway genes in response to ionizing radiation", "url": "https://doi.org/10.1016/j.cub.2024.03.019", "author": "Clark-Hachtel et al.", "datePublished": "2024", "isPartOf": { "@type": "Periodical", "name": "Current Biology" }, "identifier": "doi:10.1016/j.cub.2024.03.019" } } }, { "@type": "Question", "name": "What can a dried-out tardigrade survive?", "acceptedAnswer": { "@type": "Answer", "text": "In the dried, dormant state, tardigrades resist heat, cold, vacuum, pressure, radiation and chemical treatments, and they have been found to survive exposure to the vacuum and radiation of outer space. Add water and the animal can be rehydrated to an active form.", "citation": { "@type": "ScholarlyArticle", "name": "The tardigrade damage suppressor protein binds to nucleosomes and protects DNA from hydroxyl radicals", "url": "https://doi.org/10.7554/elife.47682", "author": "Chavez et al.", "datePublished": "2019", "isPartOf": { "@type": "Periodical", "name": "eLife" }, "identifier": "doi:10.7554/elife.47682" } } } ] }, { "@type": "MusicRecording", "name": "Windowlicker", "byArtist": { "@type": "MusicGroup", "name": "Aphex Twin" }, "genre": "IDM & Glitch Ambient Synthesis", "url": "https://open.spotify.com/track/409z4jUHpq7eIkg3N3FzZh" } ] } ```