---
title: "What the sources say about the Tardigrade (Water Bear) | AnimalTracks.wiki"
description: "54 claims from the Tardigrade (Water Bear) profile, each beside the words of the source that backs it."
image: "https://animaltracks.wiki/images/animals/tardigrade-1.webp"
canonical: "https://animaltracks.wiki/animals/tardigrade/sources/"
---

# What the sources say about the Tardigrade (Water Bear) (*Hypsibius exemplaris*)

> 54 claims from the Tardigrade (Water Bear) profile, each beside the words of the source that backs it. A "..." marks a cut in a quote and [brackets] an insertion.

Profile: [Tardigrade (Water Bear)](https://animaltracks.wiki/animals/tardigrade/)

## Gąsiorek et al. (2018). An integrative redescription of Hypsibius dujardini (Doyère, 1840), the nominal taxon for Hypsibioidea (Tardigrada: Eutardigrada). Zootaxa.

https://doi.org/10.11646/zootaxa.4415.1.2

| The page says | The source says |
| :--- | :--- |
| best known from a strain kept in many laboratories throughout the world | a commercially available strain that is maintained in many laboratories throughout the world |
| Not Evaluated | represents, in fact, a new species: H. exemplaris sp. nov. (note: stats.conservationStatus. No reference states a Red List status; this anchors the species name (described 2018) only. GBIF's copy of the Red List returns NOT_EVALUATED (code NE) for Hypsibius exemplaris Gasiorek, Stec, Morek & Michalczyk, 2018, usage key 9800250, checked 2026-09-28.) |
| A commercially sold strain kept in many laboratories throughout the world was assumed to be Hypsibius dujardini. | a commercially available strain that is maintained in many laboratories throughout the world, and assumed to represent H. dujardini sensu stricto |
| 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 | we provide the first integrated taxonomic redescription of H. dujardini ... DNA sequences for three nuclear markers ... represents, in fact, a new species: H. exemplaris sp. nov. (note: the redescription was of H. dujardini itself, not of the lab strain; the writer's 'redescription of that strain' reversed it 2018 is the paper's publication year (gasiorek-2018).) |
| 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. | a commercially available strain that is maintained in many laboratories throughout the world, and assumed to represent H. dujardini sensu stricto, represents, in fact, a new species: H. exemplaris sp. nov. (note: 2018 is the paper's publication year (gasiorek-2018).) |

## Chavez et al. (2019). The tardigrade damage suppressor protein binds to nucleosomes and protects DNA from hydroxyl radicals. eLife.

https://doi.org/10.7554/elife.47682

| The page says | The source says |
| :--- | :--- |
| Eight-legged micro-survivor | comprise a head segment in addition to four body segments that each contains two legs (note: four body segments x two legs each = eight legs) |
| the wider tardigrade phylum also includes marine species | small invertebrate animals that are found in marine, freshwater, and terrestrial habitats throughout the Earth |
| Across the phylum, tardigrades typically run about 0.1 to 1 millimeter long | They are typically about 0.1 to 1 mm in length |
| Land-dwelling tardigrades need a thin film of water to stay active. | Terrestrial tardigrades require a thin film of water to remain active. |
| A second defense may sit in the nucleus. | These findings suggest that Dsup promotes the survival of tardigrades under diverse conditions (note: 'may' keeps the source's 'suggest') |
| Dsup, a damage-suppressor protein first found in R. varieornatus, has a counterpart in H. exemplaris | Dsup was initially not identified in H. exemplaris ( Yoshida et al., 2017 ), but further analysis revealed a Dsup-like protein in this organism |
| first found in R. varieornatus | In R. varieornatus , the study of chromatin-associated factors revealed a tardigrade-specific protein, termed Dsup, for damage suppressor |
| In lab tests that version also binds to nucleosomes in chromatin, the structure DNA is packaged into, and protects DNA from hydroxyl radicals | a Dsup ortholog from the tardigrade Hypsibius exemplaris similarly binds to nucleosomes and protects DNA from hydroxyl radicals |
| hydroxyl radicals, which ionizing radiation generates in cells | hydroxyl radicals, which are generated in cells by ionizing radiation |
| the structure DNA is packaged into | DNA, which is packaged into a structure called chromatin |
| Its genome has been sequenced | the sequencing of the genomes of Ramazzottius varieornatus ( Hashimoto et al., 2016 ) and Hypsibius exemplaris ( Yoshida et al., 2017 ) |
| 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. | In the anhydrobiotic state, tardigrades are resistant to extreme conditions of heat, cold, vacuum, pressure, radiation, and chemical treatments. Remarkably, they have been found to survive exposure to the vacuum and radiation of outer |
| Add water and the animal can be rehydrated to an active form. | they undergo anhydrobiosis into a dormant dehydrated state from which they can be rehydrated to an active form |
| Tardigrades, also called water bears or moss piglets | Tardigrades, which are also known as water bears or moss piglets |
| have four body segments that each carry two legs | four body segments that each contains two legs |

## Yoshida et al. (2017). Comparative genomics of the tardigrades Hypsibius dujardini and Ramazzottius varieornatus. PLOS Biology.

https://doi.org/10.1371/journal.pbio.2002266

| The page says | The source says |
| :--- | :--- |
| Limnoterrestrial (freshwater and land), and best known from a strain kept in many laboratories throughout the world | H . dujardini , a limnoterrestrial tardigrade that can undergo anhydrobiosis only after extensive pre-exposure to drying conditions (note: Yoshida's 'H. dujardini' is H. exemplaris: chavez-2019 says 'the strain of tardigrades that was designated as Hypsibius dujardini in Yoshida et al. (2017) has since been found to be a new species that is now termed Hypsibius exemplaris'. Lab-strain clause from gasiorek-2018 below. 'Worldwide' was cut: gasiorek-2018 says the wide range belonged to misidentified H. dujardini records, and no source gives H. exemplaris a wild range.) |
| In lab culture, the green alga Chlorella vulgaris. | tardigrades were fed Chlorella vulgaris (Chlorella Industry) (note: methods, culture of strain H. dujardini Z151 (= H. exemplaris, see chavez-2019 note). Wild diet unsourced, so 'Herbivorous' was cut.) |
| Unlike its relative Ramazzottius varieornatus, which tolerates rapid desiccation | R . varieornatus , a related species with tolerance to rapid desiccation |
| H. exemplaris enters that dormant state only "after extensive pre-exposure to drying conditions." | can undergo anhydrobiosis only after extensive pre-exposure to drying conditions |
| A 2017 genome study dried it slowly, at 85% relative humidity for 48 hours | placed in a chamber maintained at 85% RH for 48 h for H . dujardini (note: 2017 is the paper's publication year; the strain dried is Z151, named H. dujardini there and H. exemplaris since (chavez-2019)) |
| counted a batch as successfully dormant when more than 90% of the animals recovered after rehydration | Successful anhydrobiosis was assumed when >90% of the samples prepared in the same chamber recovered after rehydration. (note: a success threshold in the methods, not a measured survival rate; the writer's 'more than 90% of a lab batch survives' overstated it) |
| Lab colonies of H. exemplaris are fed the green alga Chlorella vulgaris. | tardigrades were fed Chlorella vulgaris (Chlorella Industry) |

## Richaud et al. (2020). Ultrastructural analysis of the dehydrated tardigrade Hypsibius exemplaris unveils an anhydrobiotic-specific architecture. Scientific Reports.

https://doi.org/10.1038/s41598-020-61165-1

| The page says | The source says |
| :--- | :--- |
| Dries into a dormant "tun" in which its cells and mitochondria shrink | reductions in the sizes of both cells and mitochondria were detected in dehydrated animals |
| in one lab study active H. exemplaris measured about 164 micrometers | hydrated tardigrades measured 164 +/− 32 µm, while tuns measured 101 +/− 12 µm |
| H. exemplaris contracts into a compact ball called a tun | The contraction of the body in the tun was observed |
| the shape tardigrades form to reduce their body surface area and rate of evaporation | tardigrades and rotifers form a tun to reduce their body surface area and rate of evaporation |
| In one study, tuns dried for six days | we dehydrated Hypsibius exemplaris for 6 days |
| tuns dried for six days measured about 101 micrometers | tuns measured 101 +/− 12 µm |
| the cells and mitochondria inside had shrunk too | reductions in the sizes of both cells and mitochondria were detected in dehydrated animals |
| In one study, active Hypsibius exemplaris measured about 164 micrometers and tuns dried for six days about 101 | we dehydrated Hypsibius exemplaris for 6 days ... hydrated tardigrades measured 164 +/− 32 µm, while tuns measured 101 +/− 12 µm |
| and the cells and mitochondria inside had shrunk too | reductions in the sizes of both cells and mitochondria were detected in dehydrated animals |
| The researchers read the shrunken mitochondria as a sign that metabolism in a tun is minimal, with limited breathing. | we postulate that this decreased cristae size reflects the fact that the metabolism in tuns is minimal with limited breathing (note: the source's 'decreased cristae size' is the inner-membrane folds of the shrunken mitochondria; 'read as a sign' keeps 'postulate') |

## Clark-Hachtel et al. (2024). The tardigrade Hypsibius exemplaris dramatically upregulates DNA repair pathway genes in response to ionizing radiation. Current Biology.

https://doi.org/10.1016/j.cub.2024.03.019

| The page says | The source says |
| :--- | :--- |
| meets a dose of gamma rays by rapidly switching on many of its own DNA-repair genes | the tardigrade Hypsibius exemplaris suffers DNA damage upon gamma irradiation, but the damage is repaired ... irradiation induces a rapid upregulation of many DNA repair genes |
| answers gamma-ray damage by rapidly switching on many DNA-repair genes | irradiation induces a rapid upregulation of many DNA repair genes |
| Tardigrades can survive doses of ionizing radiation up to about 1,000 times the lethal dose for humans. | Tardigrades can survive remarkable doses of ionizing radiation, up to about 1,000 times the lethal dose for humans. (note: phylum scope, as the source states it; not measured for H. exemplaris in the abstract. Also covers the heading 'Radiation, a Thousand Times Over'.) |
| H. exemplaris isn't immune: gamma rays still damage its DNA. What's different is the comeback: the damage is repaired. | the tardigrade Hypsibius exemplaris suffers DNA damage upon gamma irradiation, but the damage is repaired |
| Irradiation rapidly switches on many DNA-repair genes in H. exemplaris, pushing some repair transcripts to among the most abundant in the animal. | irradiation induces a rapid upregulation of many DNA repair genes ... making some DNA repair transcripts among the most abundant transcripts in the animal |
| At least one of those genes is important to radiation tolerance in the living animal. | We show that at least one such gene is important in vivo for tardigrade radiation tolerance. |
| 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. | Tardigrades can survive remarkable doses of ionizing radiation, up to about 1,000 times the lethal dose for humans. ... the tardigrade Hypsibius exemplaris suffers DNA damage upon gamma irradiation, but the damage is repaired |
| in lab tests boosting some of its repair genes in bacteria was enough to raise the bacteria's radiation tolerance | By expressing tardigrade genes in bacteria, we validate that increased expression of some repair genes can suffice to increase radiation tolerance. |
| Radiation, Up to a Thousand Times Over | up to about 1,000 times the lethal dose for humans (note: heading for the phylum-scope figure the section's first sentence states) |
| an animal whose DNA is damaged by gamma rays and then repaired | the tardigrade Hypsibius exemplaris suffers DNA damage upon gamma irradiation, but the damage is repaired (note: vibe.reason, settled in #913) |
| it answers gamma-ray damage by rapidly switching on many DNA-repair genes | irradiation induces a rapid upregulation of many DNA repair genes (note: vibe.reason, settled in #913) |

## Malki et al. (2021). Intrinsically Disordered Tardigrade Proteins Self-Assemble into Fibrous Gels in Response to Environmental Stress. Angewandte Chemie International Edition.

https://doi.org/10.1002/anie.202109961

| The page says | The source says |
| :--- | :--- |
| Disordered proteins found only in tardigrades play an essential role in the shutdown. | tardigrade‐unique intrinsically disordered proteins have been shown to play an essential role in tardigrade anhydrobiosis (note: 'found only in tardigrades' renders the source's 'tardigrade-unique') |
| In the lab, one of this species' proteins, CAHS-8, formed long fibres and finally a gel as it grew more concentrated | CAHS‐8 from Hypsibius exemplaris ... Upon concentration, the protein is shown to successively form oligomers, long fibres, and finally gels constituted of fibres |
| soluble proteins caught in the gel's cavities kept their functional form | Soluble proteins can be encapsulated within cavities in the gel, maintaining their functional form. |

## Goldstein (2018). The Emergence of the Tardigrade Hypsibius exemplaris as a Model System. Cold Spring Harbor Protocols.

https://doi.org/10.1101/pdb.emo102301

| The page says | The source says |
| :--- | :--- |
| 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. | has a generation time of <2 wk at room temperature. Stocks of animals can be stored frozen and revived. The animals and their embryos are optically clear |
| researchers have built techniques for it that include microinjection and RNA interference | We have developed techniques for laboratory study of this system, including methods for microinjection of animals, immunolocalization, in situ hybridization, 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. | I review the development of this animal as an emerging model system, as well as recent molecular studies aimed at understanding the evolution of developmental mechanisms that underpin the evolution of animal form and at understanding how biological materials can survive extreme environments (note: 2018 is the paper's publication year (goldstein-2018).) |