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Tardigrade

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(Redirected from Water Bears)
"Tardigrada" redirects here. For the suborder of mammals, see sloth.
"Moss Piglets" redirects here. For the South Park episode, see Moss Piglets (South Park).

Tardigrade
Temporal range: Turonian –Recent Middle Cambrian stem-group fossils
Milnesium tardigradum, a eutardigrade
Echiniscus insularis, a heterotardigrade
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Subkingdom: Eumetazoa
Clade: ParaHoxozoa
Clade: Bilateria
Clade: Nephrozoa
(unranked): Protostomia
Superphylum: Ecdysozoa
(unranked): Panarthropoda
Phylum: Tardigrada
Spallanzani, 1777
Classes

Tardigrades (/ˈtɑːrdɪɡreɪdz/ ⓘ),[1] known colloquially as water bears or moss piglets,[2] are a phylum of eight-legged segmented micro-animals. They were first described by the German zoologist Johann August Ephraim Goeze in 1773, who called them Kleiner Wasserbär 'little water bear'. In 1776, the Italian biologist Lazzaro Spallanzani named them Tardigrada, which means 'slow walker'.

They live in diverse regions of Earth's biosphere – mountaintops, the deep sea, tropical rainforests, and the Antarctic. Tardigrades are among the most resilient animals known, with individual species able to survive extreme conditions – such as exposure to extreme temperatures, extreme pressures (both high and low), air deprivation, radiation, dehydration, and starvation – that would quickly kill most other known forms of life. Tardigrades have survived exposure to outer space.

There are about 1,300 known species in the phylum Tardigrada, a part of the superphylum Ecdysozoa. The earliest known fossil is from the Cambrian, some 500 million years ago. They lack several of the Hox genes found in arthropods, and the middle region of the body corresponding to an arthropod's thorax and abdomen. Instead, most of their body is homologous to an arthropod's head.

Tardigrades are usually about 0.5 mm (0.020 in) long when fully grown. They are short and plump, with four pairs of legs, each ending in claws (usually four to eight) or sticky pads. Tardigrades are prevalent in mosses and lichens and can readily be collected and viewed under a low-power microscope, making them accessible to students and amateur scientists. Their clumsy crawling and their well-known ability to survive life-stopping events have brought them into science fiction and popular culture including items of clothing, statues, soft toys and crochet patterns.

Description

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Body structure

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Tardigrade anatomy

Tardigrades have a short plump body with four pairs of hollow unjointed legs. Most range from 0.1 to 0.5 mm (0.004 to 0.020 in) in length, although the largest species may reach 1.3 mm (0.051 in). The body cavity is a haemocoel filled with a colourless fluid. The body covering is a cuticle that is replaced when the animal moults; it contains hardened (sclerotised) proteins and chitin but is not calcified. Each leg ends in one or more claws according to the species; in some species, the claws are modified as sticky pads. In marine species, the legs are telescopic. There are no lungs, gills, or blood vessels, so tardigrades rely on diffusion through the cuticle and body cavity for gas exchange.[3]

Nervous system and senses

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The tardigrade nervous system has a pair of ventral nerve cords with a pair of ganglia serving each pair of legs. The nerve cords end near the mouth at a pair of suboesophageal ganglia. These are connected by paired commissures (either side of the tube from the mouth to the pharynx) to the dorsally located cerebral ganglion or 'brain'. Also in the head are two eyespots in the brain, and several sensory cirri and pairs of hollow clavae which may be chemoreceptors.[3]

Locomotion

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Although the body is flexible and fluid-filled, locomotion does not operate mainly hydrostatically. Instead, as in arthropods, the muscles (sometimes just one or a few cells) work in antagonistic pairs that make each leg step backwards and forwards; there are also some flexors that work against hydrostatic pressure of the haemocoel. The claws help to stop the legs sliding during walking, and are used for gripping.[3]

Feeding and excretion

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Tardigrades feed by sucking animal or plant cell fluids, or on detritus. A pair of stylets pierce the prey; the pharynx muscles then pump the fluids from the prey into the gut. A pair of salivary glands secrete a digestive fluid into the mouth, and produce replacement stylets each time the animal molts.[3] Non-marine species have Malpighian tubules where the intestine joins the hindgut. Some species have excretory or other glands between or at the base of the legs.[3]

  • Video of tardigrade under the microscope
  • Living tardigrades moving around

Reproduction and life cycle

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Shed cuticle of female tardigrade, containing eggs

Most tardigrades have both male and female animals which copulate by a variety of methods. The females lay eggs. Some species appear to have no males, suggesting that parthenogenesis is common.[3]

Both sexes have a single gonad located above the intestine.[3] A pair of ducts run from the testis, opening through a single gonopore in front of the anus. Females have a single oviduct opening either just above the anus or directly into the rectum, which forms a cloaca.[3]

The male may place his sperm into the cloaca, or may penetrate the female's cuticle and place the sperm straight into her body cavity, for it to fertilise the eggs directly in the ovary. A third mechanism in some species is for the male to place the sperm under the female's cuticle; when she moults, she lays eggs into the cast cuticle, where they are fertilised.[3] Courtship occurs in some aquatic tardigrades, with the male stroking his partner with his cirri to stimulate her to lay eggs; fertilisation is then external.[3]

Up to 30 eggs are laid, depending on the species. Terrestrial tardigrade eggs have drought-resistant shells. Aquatic species either glue their eggs to a substrate or leave them in a cast cuticle. The eggs hatch within 14 days, the hatchlings using their stylets to open their egg shells.[3]

Ecology and life history

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Tardigrades are cosmopolitan, living in many environments on land, in freshwater, and in the sea. Their eggs and resistant life-cycle stages (cysts and tuns) are small and durable enough to enable long-distance transport, whether on the feet of other animals or by the wind.[3] The majority of species live in damp habitats such as on lichens, liverworts, and mosses, and directly in soil and leaf litter. In freshwater and the sea they live on and in the bottom, such as in between particles or around seaweeds. More specialised habitats include hot springs and as parasites or commensals of marine invertebrates. In soil there can be as many as 300,000 per square metre; on mosses they can reach a density of over 2 million per square metre.[3]

With the exception of 62 exclusively freshwater species, all non-marine tardigrades are found in terrestrial environments. Because the majority of the marine species belongs to Heterotardigrada, the most ancestral class, the phylum evidently has a marine origin.[4]

Environmental tolerance

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Tardigrades are not considered extremophilic because they are not adapted to exploit extreme conditions, only to endure them. This means that their chances of dying increase the longer they are exposed to the extreme environments,[5] whereas true extremophiles thrive there.[6]

Dehydrated 'tun' state

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Richtersius coronifer in active and 'tun' states.
A↔P = anterior-posterior; mg = midgut; go = gonad;
pb = pharyngeal bulb; mo = mouth; st = stylet
Scale bars = 100 μm

Tardigrades are capable of suspending their metabolism, going into a state of cryptobiosis.[3] Terrestrial and freshwater tardigrades are able to tolerate long periods when water is not available, such as when the moss or pond they are living in dries out, by drawing their legs in and forming a desiccated cyst, the cryptobiotic 'tun' state, where no metabolic activity takes place.[3] In this state, they can go without food or water for several years.[3] Further, in that state they become highly resistant to environmental stresses, including temperatures from as low as −272 °C (−458 °F) to as much as +149 °C (300 °F) (at least for short periods of time[7]), lack of oxygen,[3] vacuum,[3] ionising radiation,[3][8] and high pressure.[9]

Surviving other stresses

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Marine tardigrades such as Halobiotus crispae alternate each year (cyclomorphosis) between an active summer morph and a hibernating winter morph (a pseudosimplex) that can resist freezing and low salinity, but which remains active throughout. Reproduction however takes place only in the summer morph.[3]

Tardigrades can survive impacts up to about 900 metres per second, and momentary shock pressures up to about 1.14 gigapascals.[10]

Exposure to space (vacuum and ultraviolet)

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The 2007 FOTON-M3 mission carrying the BIOPAN astrobiology payload (illustrated) exposed tardigrades to vacuum, solar ultraviolet, or both, showing their ability to survive in the space environment.

Tardigrades have survived exposure to space. In 2007, dehydrated tardigrades were taken into low Earth orbit on the FOTON-M3 mission carrying the BIOPAN astrobiology payload. For 10 days, groups of tardigrades, some of them previously dehydrated, some of them not, were exposed to the hard vacuum of space, or vacuum and solar ultraviolet radiation.[11] Back on Earth, more than 68% of the subjects protected from solar ultraviolet radiation were reanimated within 30 minutes following rehydration; although subsequent mortality was high, many produced viable embryos.[11]

In contrast, hydrated samples exposed to the combined effect of vacuum and full solar ultraviolet radiation had significantly reduced survival, with only three subjects of Milnesium tardigradum surviving.[11] The space vacuum did not much affect egg-laying in either R. coronifer or M. tardigradum, whereas UV radiation did reduce egg-laying in M. tardigradum.[12] In 2011, Italian scientists sent tardigrades on board the International Space Station along with extremophiles on STS-134.[13] They concluded that microgravity and cosmic radiation "did not significantly affect survival of tardigrades in flight" and that tardigrades could be useful in space research.[14][15]

In 2019, a capsule containing tardigrades in a cryptobiotic state was on board the Israeli lunar lander Beresheet which crashed on the Moon; they were described as unlikely to have survived the impact.[10] Despite tardigrades' ability to survive in space, tardigrades on Mars would still need food.[16]

Damage protection proteins

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Tardigrades' ability to remain desiccated for long periods of time was thought to depend on high levels of the sugar trehalose,[17] common in organisms that survive desiccation.[18] However, tardigrades do not synthesize enough trehalose for this function.[17] Instead, tardigrades produce intrinsically disordered proteins in response to desiccation. Three of these are specific to tardigrades and have been called tardigrade specific proteins. These may protect membranes from damage by associating with the polar heads of lipid molecules.[19] The proteins may also form a glass-like matrix that protects cytoplasm from damage during desiccation.[20]

Tardigrade DNA is protected from radiation by the Dsup ("damage suppressor") protein.[21] The Dsup proteins of Ramazzottius varieornatus and Hypsibius exemplaris promote survival by binding to nucleosomes and protecting chromosomal DNA from hydroxyl radicals.[22] The Dsup protein of R. varieornatus confers resistance to ultraviolet-C by upregulating DNA repair genes.[23]

Taxonomic history

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Johann August Ephraim Goeze originally named the tardigrade Kleiner Wasserbär, meaning 'little water-bear' in German (today, Germans often call them Bärtierchen 'little bear-animal').[24][25] The name water bear comes from the way they walk, reminiscent of a bear's gait. The name Tardigradum means 'slow walker' and was given by Lazzaro Spallanzani in 1776.[26][5] In 1834, C.A.S. Schulze gave the first formal description of a tardigrade, Macrobiotus hufelandi, in a work subtitled "a new animal from the crustacean class, capable of reviving after prolonged asphyxia and dryness".[27][28] Ferdinand Richters worked on the taxonomy of tardigrades from 1900 to 1913, with studies of Nordic, Arctic, marine, and South American species; he described many species at this time,[29][30] and in 1926 set up the class Eutardigrada.[31][32] In 1927, Ernst Marcus set up the class Heterotardigrada.[33] In 1937 Gilbert Rahm, studying the fauna of Japan's hot springs, distinguished the class Mesotardigrada, with a single species Thermozodium esakii;[34] its validity is now doubted.[35] In 1962, Giuseppe Ramazzotti proposed the phylum Tardigrada.[36] In 2019, Noemi Guil and colleagues proposed to promote the order Apochela to the new class Apotardigrada.[37] There are about 1,300 described species in the phylum Tardigrada, a part of the superphylum Ecdysozoa.[38]

Evolution

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Evolutionary history

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Further information: Panarthropoda

Tardigrade fossils are rare. The only known specimens are those from mid-Cambrian deposits in Siberia (in the Orsten fauna) and a few specimens in amber from the Cretaceous of North America and the Neogene of Dominica.[3][39] The Siberian fossils differ from living tardigrades in several ways. They have three pairs of legs rather than four, they have a simplified head morphology, and they have no posterior head appendages, but they share with modern tardigrades their columnar cuticle construction. Scientists think they represent a stem group of living tardigrades.[40]

Multiple lines of evidence show that tardigrades are secondarily miniaturized from a larger ancestor,[44] probably a lobopodian, perhaps resembling the mid-Cambrian Aysheaia, which many analyses place close to the divergence of the tardigrade lineage.[42][43] An alternative hypothesis derives tactopoda from a clade encompassing dinocaridids and Opabinia.[45] The enigmatic panarthropodan Sialomorpha found in 30-million year old Dominican amber, while not a tardigrade, shows some apparent affinities.[46] A 2023 morphological analysis concluded that luolishaniids, a group of Cambrian lobopodians, might be the tardigrades' closest known relatives.[41]

Tardigrades lack several of the Hox genes found in arthropods, and a large intermediate region of the body axis. In insects, this corresponds to the entire thorax and abdomen. Practically the whole body, except for the last pair of legs, is made up of just the segments that are homologous to the head region in arthropods. This implies that tardigrades evolved from an ancestral ecdysozoan with a longer body and more segments.[47]

Tardigrade body plan compared to arthropods, onychophora, and annelids. Tardigrades have lost the whole middle section of the ecdysozoan body plan, and its Hox genes.[47] Their relationships with arthropods and onychophora are debated.[48]

The oldest remains of modern tardigrades are those of Milnesium swolenskyi, belonging to the living genus Milnesium known from a Late Cretaceous (Turonian) aged specimen of New Jersey amber, around 90 mya. Another fossil species, Beorn leggi, is known from a Late Campanian (~72 mya) specimen of Canadian amber, belonging to the family Hypsibiidae.[49] The related hypsibioidean Aerobius dactylus was found in the same amber piece.[50][51] The youngest known fossil tadigrade genus, Paradoryphoribius, was discovered in amber dated to about 16 mya.[39]

Morphological and molecular phylogenetics studies have attempted to define how tardigrades relate to other ecdysozoan groups; alternative placements have been proposed within the Panarthropoda.[52] The Tactopoda hypothesis holds that Tardigrada are sister to Arthropoda; the Antennopoda hypothesis is that Tardigrada are sister to (Onychophora + Arthropoda; and the Lobopodia (sensu Smith & Goldstein 2017) hypothesis is that Tardigrada are sister to Onychophora. The relationships have been debated on the basis of conflicting evidence.[48]

Phylogeny

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In 2012, the phylogeny of the phylum was studied using molecular markers (ribosomal RNA), finding that the Heterotardigrada and Arthrotardigrada seemed to be paraphyletic.[53]

Tardigrada

"Arthrotardigrada"

Echiniscoidea

Eutardigrada
Apochela

Milnesiidae

Parachela

Isohypsibiodea

Macrobiotoidea

Hypsibioidea

In 2018, a report integrating multiple morphological and molecular studies concluded that while the Arthrotardigrada appear to be paraphyletic, the Heterotardigrada is an accepted clade. All the lower-level taxa have been much reorganized, but the major groupings remain in place.[54]

Tardigrada
Heterotardigrada
Eutardigrada
Apochela

Milnesiidae

Parachela

Isohypsibiodea

Macrobiotoidea

Hypsibioidea

Genomics

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Tardigrade genomes vary widely in size.[55] Hypsibius exemplaris (formerly Hypsibius dujardini) has a compact genome of 100 megabase pairs[52] and a generation time of about two weeks; it can be cultured indefinitely and cryopreserved.[56] The genome of Ramazzottius varieornatus, one of the most stress-tolerant species of tardigrades, is about half as big, at 55 Mb.[52] About 1.6% of its genes are the result of horizontal gene transfer from other species, not implying any dramatic effect.[52]

In culture and society

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Popularity

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Tardigrades are common in mosses and lichens on walls and roofs, and can readily be collected and viewed under a low-power microscope. If they are dry, they can be reanimated on a microscope slide by adding a little water, making them accessible to beginning students and amateur scientists.[57] Current Biology attributed their popularity to "their clumsy crawling [which] is about as adorable as can be."[58] The zoologists James F. Fleming and Kazuhuru Arakawa called them "a charismatic phylum".[35] They have been famous[59] for their ability to survive life-stopping events such as being dried out since Spallanzani first resuscitated them from some dry sediment in a gutter in the 18th century.[59] These traits have made them appear in various kinds of science fiction an other pop culture.[60][61] Live Science notes that they are popular enough to appear on merchandise like clothes, earrings, and keychains, with crochet patterns for people to make their own tardigrade.[62] The Dutch artist Arno Coenen [nl] created statues for St Eusebius' Church, Arnhem of microscopic organisms including a tardigrade and a coronavirus.[63]

In books and music

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The short-story "Bathybia" by Douglas Mawson, published in the 1908 book Aurora Australis, printed in the Antarctic, deals with an expedition to the South Pole where the team encounters giant mushrooms and arthropods. The team watches a giant tardigrade fighting a similarly enormous rotifer; another giant water bear bites a man's toe, rendering him comatose for half an hour. Finally, a four-foot-long tardigrade, waking from hibernation, scares the narrator from his sleep, and he realizes it was all a dream.[64][65]

Musician Cosmo Sheldrake imagines himself a tardigrade in his 2015 "Tardigrade Song".[66]

In film and TV

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When the characters in the superhero films Ant-Man (2015) and Ant-Man and the Wasp (2018) shrink themselves to enter the "Quantum Realm", they encounter tardigrades.[67] In the 2015 sci-fi horror film Harbinger Down, the characters have to deal with deadly mutated tardigrades, the result of Cold War experiments.[68] In the 2017 Star Trek: Discovery, the alien "Ripper" creature is a huge version of a terrestrial tardigrade, in symbiosis with fungi.[69][68] The 2017 South Park episode "Moss Piglets" involves a science experiment in which tardigrades learn to dance to the music of Taylor Swift.[70] The 2018 Family Guy episode "Big Trouble in Little Quahog" sees Stewie and Brian shrunk to microscopic size, during which they meet a group of friendly tardigrades or "water bears" who help them.[71]

See also

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References

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  1. ^ "tardigrade". Dictionary.com Unabridged (Online). n.d.
  2. ^ Miller, William (2017-02-06). "Tardigrades". American Scientist. Retrieved 2018-04-13.
  3. ^ a b c d e f g h i j k l m n o p q r s t u Brusca, Richard C.; Moore, Wendy; Shuster, Stephen M. (2016). Invertebrates (3rd ed.). Sinauer Associates. pp. 711–717. ISBN 978-1605353753.
  4. ^ van Straalen, Nico M. (August 2021). "Evolutionary terrestrialization scenarios for soil invertebrates". Pedobiologia. 87–88: 150753. Bibcode:2021Pedob..8750753V. doi:10.1016/j.pedobi.2021.150753.
  5. ^ a b Bordenstein, Sarah. "Tardigrades (Water Bears)". Microbial Life Educational Resources. National Science Digital Library. Retrieved 2014-01-24.
  6. ^ Rothschild, Lynn J.; Mancinelli, Rocco L. (2001). "Life in extreme environments". Nature. 409 (6823): 1092–1101. Bibcode:2001Natur.409.1092R. doi:10.1038/35059215. PMID 11234023. S2CID 529873.
  7. ^ Horikawa, Daiki D. (2012). "Survival of Tardigrades in Extreme Environments: A Model Animal for Astrobiology". In Altenbach, Alexander V.; Bernhard, Joan M.; Seckbach, Joseph (eds.). Anoxia. Cellular Origin, Life in Extreme Habitats and Astrobiology. Vol. 21. pp. 205–217. doi:10.1007/978-94-007-1896-8_12. ISBN 978-94-007-1895-1.
  8. ^ Horikawa, Daiki D.; Sakashita, Tetsuya; Katagiri, Chihiro; Watanabe, Masahiko; Kikawada, Takahiro; et al. (2006). "Radiation tolerance in the tardigrade Milnesium tardigradum". International Journal of Radiation Biology. 82 (12): 843–848. doi:10.1080/09553000600972956. PMID 17178624. S2CID 25354328.
  9. ^ Seki, Kunihiro; Toyoshima, Masato (1998). "Preserving tardigrades under pressure". Nature. 395 (6705): 853–854. Bibcode:1998Natur.395..853S. doi:10.1038/27576. S2CID 4429569.
  10. ^ a b O'Callaghan, Jonathan (2021). "Hardy water bears survive bullet impacts—up to a point". Science. doi:10.1126/science.abj5282. S2CID 236376996.
  11. ^ a b c Jönsson, K. Ingemar; Rabbow, Elke; Schill, Ralph O.; Harms-Ringdahl, Mats; Rettberg, Petra (2008). "Tardigrades survive exposure to space in low Earth orbit". Current Biology. 18 (17): R729–R731. Bibcode:2008CBio...18.R729J. doi:10.1016/j.cub.2008.06.048. PMID 18786368. S2CID 8566993.
  12. ^ Jönsson, K. Ingemar; Rabbow, Elke; Schill, Ralph O.; Harms-Ringdahl, Mats; Rettberg, Petra (September 2008). "Tardigrades survive exposure to space in low Earth orbit". Current Biology. 18 (17): R729–R731. Bibcode:2008CBio...18.R729J. doi:10.1016/j.cub.2008.06.048. PMID 18786368. S2CID 8566993.
  13. ^ NASA Staff (17 May 2011). "BIOKon In Space (BIOKIS)". NASA. Archived from the original on 17 April 2011. Retrieved 2011-05-24.
  14. ^ Rebecchi, L.; Altiero, T.; Rizzo, A. M.; Cesari, M.; Montorfano, G.; Marchioro, T.; Bertolani, R.; Guidetti, R. (2012). "Two tardigrade species on board of the STS-134 space flight" (PDF). 12th International Symposium on Tardigrada. p. 89. hdl:2434/239127. ISBN 978-989-96860-7-6.
  15. ^ Reuell, Peter (2019-07-08). "Harvard study suggests asteroids might play key role in spreading life". Harvard Gazette. Retrieved 2019-11-30.
  16. ^ Ledford, Heidi (2008-09-08). "Spacesuits optional for 'water bears'". Nature. doi:10.1038/news.2008.1087.
  17. ^ a b Hibshman, Jonathan D.; Clegg, James S.; Goldstein, Bob (2020-10-23). "Mechanisms of Desiccation Tolerance: Themes and Variations in Brine Shrimp, Roundworms, and Tardigrades". Frontiers in Physiology. 11: 592016. doi:10.3389/fphys.2020.592016. PMC 7649794. PMID 33192606.
  18. ^ Kamilari, Maria; Jørgensen, Aslak; Schiøtt, Morten; Møbjerg, Nadja (2019-07-24). "Comparative transcriptomics suggest unique molecular adaptations within tardigrade lineages". BMC Genomics. 20 (1): 607. doi:10.1186/s12864-019-5912-x. ISSN 1471-2164. PMC 6652013. PMID 31340759.
  19. ^ Boothby, Thomas C.; Tapia, Hugo; Brozena, Alexandra H.; Piszkiewicz, Samantha; Smith, Austin E.; et al. (2017). "Tardigrades Use Intrinsically Disordered Proteins to Survive Desiccation". Molecular Cell. 65 (6): 975–984.e5. doi:10.1016/j.molcel.2017.02.018. PMC 5987194. PMID 28306513.
  20. ^ Boothby, Thomas C.; Piszkiewicz, Samantha; Holehouse, Alex; Pappu, Rohit V.; Pielak, Gary J. (December 2018). "Tardigrades use intrinsically disordered proteins to survive desiccation". Cryobiology. 85: 137–138. doi:10.1016/j.cryobiol.2018.10.077. hdl:11380/1129511. S2CID 92411591.
  21. ^ Hashimoto, Takuma; Horikawa, Daiki D; Saito, Yuki; Kuwahara, Hirokazu; Kozuka-Hata, Hiroko; et al. (2016). "Extremotolerant tardigrade genome and improved radiotolerance of human cultured cells by tardigrade-unique protein". Nature Communications. 7: 12808. Bibcode:2016NatCo...712808H. doi:10.1038/ncomms12808. PMC 5034306. PMID 27649274.
  22. ^ Chavez, Carolina; Cruz-Becerra, Grisel; Fei, Jia; Kassavetis, George A.; Kadonaga, James T. (2019-10-01). "The tardigrade damage suppressor protein binds to nucleosomes and protects DNA from hydroxyl radicals". eLife. 8. doi:10.7554/eLife.47682. ISSN 2050-084X. PMC 6773438. PMID 31571581.
  23. ^ Ricci, Claudia; Riolo, Giulia; Marzocchi, Carlotta; Brunetti, Jlenia; Pini, Alessandro; Cantara, Silvia (2021-09-27). "The Tardigrade Damage Suppressor Protein Modulates Transcription Factor and DNA Repair Genes in Human Cells Treated with Hydroxyl Radicals and UV-C". Biology. 10 (10): 970. doi:10.3390/biology10100970. PMC 8533384. PMID 34681069.
  24. ^ Greven, Hartmut (2015). "About the little water bear: A commented translation of GOEZE'S note "Ueber den kleinen Wasserbär" from 1773". Acta Biologica Benrodis. 17: 1–27. Retrieved 27 September 2024.
  25. ^ Cross, Ryan (2016-11-07). "Secrets of the tardigrade". C&EN Global Enterprise. 94 (44): 20–21. doi:10.1021/cen-09444-scitech1. Retrieved 31 May 2021.
  26. ^ Spallanzani, Lazzaro (1776). Opuscoli di fisica animale, e vegetabile [Booklets on the structure of animals and plants] (in Italian). Modena: Presso La Societa' Tipografica.
  27. ^ Bertolani, Roberto; Rebecchi, Lorena; Giovannini, Ilaria; Cesari, Michele (2011-08-17). "DNA barcoding and integrative taxonomy of Macrobiotus hufelandi C.A.S. Schultze 1834, the first tardigrade species to be described, and some related species". Zootaxa. 2997 (1): 19–36. doi:10.11646/zootaxa.2997.1.2.
  28. ^ Schultze, Karl August Sigismund (1834). Macrobiotus hufelandii, animal e crustaceorum classe novum, reviviscendi post diuturnam asphyxiam et ariditatem potens [Macrobiotus hufelandii, a new animal from the crustacean class, capable of reviving after prolonged asphyxia and dryness] (in Latin). Curths.
  29. ^ Mach, Martin. "Prof. Ferdinand Richters". Water Bear web base. Retrieved 15 December 2024. (with full Richters bibliography; first published in Bärtierchen-Journal, issue 62)
  30. ^ Michalczyk, Łukasz; Kaczmarek, Łukasz (24 July 2013). "The Tardigrada Register: a comprehensive online data repository for tardigrade taxonomy". Journal of Limnology. 72 (1s). doi:10.4081/jlimnol.2013.s1.e22. Retrieved 15 December 2024.
  31. ^ "Eutardigrada Richters, 1926". Integrated Taxonomic Information System. Retrieved 16 December 2024.
  32. ^ Richters, Ferdinand; Krumbach, T.H. (1926). "Tardigrada". In Kŭkenthal, W.; Krumbach, T.H. (eds.). Handbook of Zoology. Vol. 3. Berlin and Leipzig. pp. 1–68.{{cite book}}: CS1 maint: location missing publisher (link)
  33. ^ "Heterotardigrada Marcus, 1927". Integrated Taxonomic Information System. Retrieved 16 December 2024.
  34. ^ Rahm, Gilbert (1937). "A new ordo of tardigrades from the hot springs of Japan (Furu-yu section, Unzen)". 日本動物学彙報 (Bulletin of the Zoological Society of Japan). 16 (4): 345–352.
  35. ^ a b Fleming, James F.; Arakawa, Kazuharu (2021). "Systematics of tardigrada: A reanalysis of tardigrade taxonomy with specific reference to Guil et al. (2019)". Zoologica Scripta. 50 (3): 376–382. doi:10.1111/zsc.12476.
  36. ^ Ramazzotti, Giuseppe (1962). "Il Phylum Tardigrada" [The Phylum Tardigrada]. Memorie dell'Istituto Italiano di Idrobiologia (in Italian). 16: 1–595.
  37. ^ Guil, Noemi; Jørgensen, Aslak; Kristensen, Reinhardt (2019). "An upgraded comprehensive multilocus phylogeny of the Tardigrada tree of life". Zoologica Scripta. 48 (1): 120–137. doi:10.1111/zsc.12321. ISSN 0300-3256.
  38. ^ Degma, Peter; Bertolani, Roberto; Guidetti, Roberto (2021). "Actual checklist of Tardigrada species (2009–2021, 40th Edition: 19-07-2021)" (PDF). Università di Modena e Reggio Emilia. doi:10.25431/11380_1178608. Retrieved 2023-12-10.
  39. ^ a b Mapalo, M. A.; Robin, N.; Boudinot, B. E.; Ortega-Hernández, J.; Barden, P. (2021). "A tardigrade in Dominican amber". Proceedings of the Royal Society B: Biological Sciences. 288 (1960). Article 20211760. doi:10.1098/rspb.2021.1760. PMC 8493197. PMID 34610770.
  40. ^ Budd, Graham E (2001). "Tardigrades as 'Stem-Group Arthropods': The Evidence from the Cambrian Fauna". Zoologischer Anzeiger. 240 (3–4): 265–79. Bibcode:2001ZooAn.240..265B. doi:10.1078/0044-5231-00034.
  41. ^ a b Kihm, Ji-Hoon; Smith, Frank W.; Kim, Sanghee; Rho, Hyun Soo; Zhang, Xingliang; Liu, Jianni; Park, Tae-Yoon S. (2023). "Cambrian lobopodians shed light on the origin of the tardigrade body plan". Proceedings of the National Academy of Sciences. 120 (28): e2211251120. Bibcode:2023PNAS..12011251K. doi:10.1073/pnas.2211251120. PMC 10334802. PMID 37399417.
  42. ^ a b Fortey, Richard A.; Thomas, Richard H. (2001). Arthropod Relationships. Chapman & Hall. p. 383. ISBN 978-0-412-75420-3.
  43. ^ a b Smith, Martin R.; Ortega-Hernández, Javier (2014). "Hallucigenia's onychophoran-like claws and the case for Tactopoda" (PDF). Nature. 514 (7522): 363–366. Bibcode:2014Natur.514..363S. doi:10.1038/nature13576. PMID 25132546. S2CID 205239797.
  44. ^ Gross, Vladimir; Treffkorn, Sandra; Reichelt, Julian; Epple, Lisa; Lüter, Carsten; Mayer, Georg (2018). "Miniaturization of tardigrades (water bears): Morphological and genomic perspectives". Arthropod Structure & Development. 48: 12–19. doi:10.1016/j.asd.2018.11.006. PMID 30447338. S2CID 53669741.
  45. ^ Budd, Graham E. (1996). "The morphology of Opabinia regalis and the reconstruction of the arthropod stem-group". Lethaia. 29 (1): 1–14. Bibcode:1996Letha..29....1B. doi:10.1111/j.1502-3931.1996.tb01831.x.
  46. ^ Poinar, George; Nelson, Diane R. (September 28, 2019). "A new microinvertebrate with features of mites and tardigrades in Dominican amber". Invertebrate Biology. 138 (4). doi:10.1111/ivb.12265. S2CID 204157733.
  47. ^ a b Smith, Frank W.; Boothby, Thomas C.; Giovannini, Ilaria; Rebecchi, Lorena; Jockusch, Elizabeth L.; Goldstein, Bob (1 January 2016). "The Compact Body Plan of Tardigrades Evolved by the Loss of a Large Body Region". Current Biology. 26 (2): 224–229. Bibcode:2016CBio...26..224S. doi:10.1016/j.cub.2015.11.059. hdl:11380/1083953. PMID 26776737.
  48. ^ a b Smith, Frank W.; Goldstein, Bob (2017-05-01). "Segmentation in Tardigrada and diversification of segmental patterns in Panarthropoda". Arthropod Structure & Development. Evolution of Segmentation. 46 (3): 328–340. Bibcode:2017ArtSD..46..328S. doi:10.1016/j.asd.2016.10.005. PMID 27725256.
  49. ^ Cooper, Kenneth W. (1964). "The first fossil tardigrade: Beorn leggi, from Cretaceous Amber". Psyche: A Journal of Entomology. 71 (2): 41–48. doi:10.1155/1964/48418.
  50. ^ Mapalo, Marc A.; Wolfe, Joanna M.; Ortega-Hernández, Javier (2024-08-06). "Cretaceous amber inclusions illuminate the evolutionary origin of tardigrades". Communications Biology. 7 (1): 953. doi:10.1038/s42003-024-06643-2. ISSN 2399-3642. PMC 11303527. PMID 39107512.
  51. ^ Guidetti, Roberto; Bertolani, Roberto (2018), Schill, Ralph O. (ed.), "Paleontology and Molecular Dating", Water Bears: The Biology of Tardigrades, Zoological Monographs, vol. 2, Cham: Springer International Publishing, pp. 131–143, doi:10.1007/978-3-319-95702-9_5, ISBN 978-3-319-95701-2, retrieved 2020-11-24
  52. ^ a b c d Yoshida, Yuki; Koutsovoulos, Georgios; Laetsch, Dominik R.; Stevens, Lewis; Kumar, Sujai; et al. (2017-07-27). Tyler-Smith, Chris (ed.). "Comparative genomics of the tardigrades Hypsibius dujardini and Ramazzottius varieornatus". PLOS Biology. 15 (7): e2002266. doi:10.1371/journal.pbio.2002266. PMC 5531438. PMID 28749982.
  53. ^ Guil, Noemí; Giribet, Gonzalo (2012). "A comprehensive molecular phylogeny of tardigrades—adding genes and taxa to a poorly resolved phylum-level phylogeny". Cladistics. 28 (1): 21–49. doi:10.1111/j.1096-0031.2011.00364.x. PMID 34856729.
  54. ^ Jørgensen, Aslak; Kristensen, Reinhardt M.; Møbjerg, Nadja (2018). "Phylogeny and Integrative Taxonomy of Tardigrada". Water Bears: The Biology of Tardigrades. Vol. 2. Springer International Publishing. pp. 95–114. doi:10.1007/978-3-319-95702-9_3. ISBN 978-3-319-95701-2.
  55. ^ "Tardigrades". Animal Genome Size Database.
  56. ^ Gabriel, Willow N.; McNuff, Robert; Patel, Sapna K.; Gregory, T. Ryan; Jeck, William R.; Jones, Corbin D.; Goldstein, Bob (2007). "The tardigrade Hypsibius dujardini, a new model for studying the evolution of development". Developmental Biology. 312 (2): 545–559. doi:10.1016/j.ydbio.2007.09.055. PMID 17996863.
  57. ^ Shaw, Michael W. "How to Find Tardigrades". Tardigrade USA. Archived from the original on 10 February 2014. Retrieved 2013-01-14.
  58. ^ Goldstein, Bob; Blaxter, Mark (2002). "Tardigrades". Current Biology. 12 (14): R475. Bibcode:2002CBio...12.R475G. doi:10.1016/S0960-9822(02)00959-4. PMID 12176341.
  59. ^ a b Marshall, Michael (20 March 2021). "Tardigrades: nature's great survivors". The Observer.
  60. ^ Brenner, Kelly (2020). Nature Obscura: A City's Hidden Natural World. Mountaineers Books. p. 40. ISBN 978-1-68051-208-3.
  61. ^ Murphy, Coleen T. (2023). How We Age: The Science of Longevity. Princeton University Press. p. 180. ISBN 978-0-691-25033-5.
  62. ^ Saplakoglu, Yasemin (29 October 2018). "The Best Gifts for Tardigrade Lovers". Live Science.
  63. ^ "Eusebius Church Arnhem, Netherlands". Atlas Obscura. 3 January 2023. Retrieved 14 December 2024.
  64. ^ Blum, Hester (2019). The News at the Ends of the Earth: The Print Culture of Polar Exploration (PDF). Duke University Press. p. 170. ISBN 9781478004486.
  65. ^ Mawson, Douglas (July 1908). "Bathybia". In Shackleton, Ernest (ed.). Aurora Australis. British Antarctic Expedition. pp. 179–213.
  66. ^ "Cosmo Sheldrake - Tardigrade Song". Folk Radio UK - Folk Music Magazine. 2 February 2015. Retrieved 21 September 2019.
  67. ^ "How the Quantum Realm could play into future Marvel films". The Daily Dot. 10 July 2018. Retrieved 29 July 2018.
  68. ^ a b Blaxter, Mark; Kazuharu, Arakawa (March 2018). "Tardigrades in space". The Biologist. 65 (1): 16.
  69. ^ "The Scientific Truth About Ripper the 'Star Trek' Tardigrade Is a Huge Relief". Inverse. 10 October 2017. Retrieved 5 September 2018.
  70. ^ Placido, Dani Di. "'South Park' Review: Cartman Creates A Monster In 'Moss Piglets'". Forbes. Retrieved 29 July 2018.
  71. ^ Yang, Nicole (22 October 2018). "Kyrie Irving got a credit in the most recent episode of 'Family Guy'. Meet "Vernon The Water Bear."". Boston Globe Media Partners, LLC. Retrieved 22 October 2018.
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