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Tardigrades represent a phylum of very small aquatic animals in which many species have evolved adaptations to survive under extreme environmental conditions, such as desiccation and freezing. Studies on several species have documented that tardigrades also belong to the most radiation-tolerant animals on Earth. This paper gives an overview of our current knowledge on radiation tolerance of tardigrades, with respect to dose-responses, developmental stages, and different radiation sources. The molecular mechanisms behind radiation tolerance in tardigrades are still largely unknown, but omics studies suggest that both mechanisms related to the avoidance of DNA damage and mechanisms of DNA repair are involved. The potential of tardigrades to provide knowledge of importance for medical sciences has long been recognized, but it is not until recently that more apparent evidence of such potential has appeared. Recent studies show that stress-related tardigrade genes may be transfected to human cells and provide increased tolerance to osmotic stress and ionizing radiation. With the recent sequencing of the tardigrade genome, more studies applying tardigrade omics to relevant aspects of human medicine are expected. In particular, the cancer research field has potential to learn from studies on tardigrades about molecular mechanisms evolved to maintain genome integrity.

Background Tardigrades are renowned for their ability to enter cryptobiosis (latent life) and endure extreme stress, including desiccation and freezing. Increased focus is on revealing molecular mechanisms underlying this tolerance. Here, we provide the first transcriptomes from the heterotardigrade Echiniscoides cf. sigismundi and the eutardigrade Richtersius cf. coronifer, and compare these with data from other tardigrades and six eukaryote models. Investigating 107 genes/gene families, our study provides a thorough analysis of tardigrade gene content with focus on stress tolerance. Results E. cf. sigismundi, a strong cryptobiont, apparently lacks expression of a number of stress related genes. Most conspicuous is the lack of transcripts from genes involved in classical Non-Homologous End Joining. Our analyses suggest that post-cryptobiotic survival in tardigrades could rely on high fidelity transcription-coupled DNA repair. Tardigrades seem to lack many peroxins, but they all have a comprehensive number of genes encoding proteins involved in antioxidant defense. The “tardigrade unique proteins” (CAHS, SAHS, MAHS, RvLEAM), seem to be missing in the heterotardigrade lineage, revealing that cryptobiosis in general cannot be attributed solely to these proteins. Our investigation further reveals a unique and highly expressed cold shock domain. We hypothesize that the cold shock protein acts as a RNA-chaperone involved in regulation of translation following freezing. Conclusions Our results show common gene family contractions and expansions within stress related gene pathways in tardigrades, but also indicate that evolutionary lineages have a high degree of divergence. Different taxa and lineages may exhibit unique physiological adaptations towards stress conditions involving possible unknown functional homologues and/or novel physiological and biochemical mechanisms. To further substantiate the current results genome assemblies coupled with transcriptome data and experimental investigations are needed from tardigrades belonging to different evolutionary lineages. Electronic supplementary material The online version of this article (10.1186/s12864-019-5912-x) contains supplementary material, which is available to authorized users.

Water is essential for living organisms. Terrestrial organisms are incessantly exposed to the stress of losing water, desiccation stress. Avoiding the mortality caused by desiccation stress, many organisms acquired molecular mechanisms to tolerate desiccation. Larvae of the African midge, Polypedilum vanderplanki, and its embryonic cell line Pv11 tolerate desiccation stress by entering an ametabolic state, anhydrobiosis, and return to active life after rehydration. The genes related to desiccation tolerance have been comprehensively analyzed, but transcriptional regulatory mechanisms to induce these genes after desiccation or rehydration remain unclear. Here, we comprehensively analyzed the gene regulatory network in Pv11 cells and compared it with that of Drosophila melanogaster, a desiccation sensitive species. We demonstrated that nuclear transcription factor Y subunit gamma-like, which is important for drought stress tolerance in plants, and its transcriptional regulation of downstream positive feedback loops have a pivotal role in regulating various anhydrobiosis-related genes. This study provides an initial insight into the systemic mechanism of desiccation tolerance.

Tardigrades are aquatic microinvertebrates (generally they measure 0,05-1,2 mm) that feature four pairs of telescoping legs terminated in claws or digits and a have fairly characteristic buccal apparatus. They are known due to their ability to undergo cryptobiosis, an extremely environmentally resistant state. Despite this, little is know about the diversity and distribution of the phylum Tardigrada, mostly due to the small size and the fragility of their bodies, that require specific handling and laboratory instruments. In Brazil the limno-terrestrial tardigrades were not studied since the pioneers studies in the decades of 1940 and 1950. The present study aims to describe a new species of the genus Milnesium (class Eutardigrada, order Apochela, family Milnesiidae), collected from trees in the Institute of Biology, University of Campinas, Sao Paulo, Brazil, using modern morphological techniques, such as morphometrics, differential interference contrast (DIC) microscopy, scanning electron microscopy (SEM), and UV autofluorescence. This Milnesium sp. nov. is characterized by its smooth cuticle, six peribuccal lamellae of unequal size, short cuticular bars under the claws IV, a claw configuration of [3-3]-[3-3] with internal and anterior spurs larger than external and posterior spurs, and pseudoplates on the dorsum.

The year 2002 marked the tercentenary of Antonie van Leeuwenhoek’s discovery of desiccation tolerance in animals. This remarkable phenomenon to sustain ‘life’ in the absence of water can be revived upon return of hydrating conditions. Today, one of the global challenges is coping with climate change-related factors, especially temperature-humidity imbalance. Under such adverse circumstances, desiccation tolerance remains a prime secret of several plants and few animals to escape the hostile consequences of fluctuating hydroperiodicity patterns in their habitats. Among lower animals, insects, in particular, have demonstrated profound mechanisms by virtue of which they thrive under physiological water deficits without compromising on revival and survival upon rehydration. The focus of this review is to compile the enormous research insights on insect desiccation tolerance gathered over the past several decades from numerous laboratories worldwide working on different insect groups. We provide a comparative overview of species-specific behavioural changes, adjustments in physiological biochemistry and cellular and molecular mechanisms as few of the noteworthy desiccation-responsive survival kits in insects. Finally, we highlight the role of insects as potential candidate models in tracking global warming which will form the basis for translational research to mitigate periods of climatic uncertainty predicted for the future.

Organisms having tolerances against extreme environments produce and accumulate stress proteins and/or sugars in cells against the extreme environment such as high or low temperature, drying, and so forth. Sugars and/or polyols are known to prevent protein denaturation and enzyme deactivation. In particular, trehalose has received considerable attention because of its association with cryptobiosis and anhydrobiosis. This study focuses on the restoration of acid-denatured amyloid transition of myoglobin by trehalose. Myoglobin is known to proceed amyloidogenic reaction under denaturation conditions. We found that acid-denatured myoglobin at an initial process of amyloidogenic reaction (helix-to-sheet transition followed by oligomerization) at 25 °C was substantially restored to its native structure by trehalose. This action was prominent during the early stage of amyloid formation. Recent results showed that sugars are preferentially excluded from the protein surface to preserve its hydration shell and stabilize the protein structure against chemical and thermal denaturation. Therefore, the present results suggest that trehalose will restore the tightly bound water molecules around the hotspot (G-helix) of myoglobin on the amyloid transition by its intrinsic preservative action of the native hydration shell against denaturation. The present finding on the restorative action by trehalose could provide new insights into protein folding and amyloidosis.

Yeast cells are able to transition into a state of anhydrobiosis (temporary reversible suspension of metabolism) under conditions of desiccation. One of the most efficient approaches for understanding the mechanisms underlying resistance to dehydration-rehydration is to identify yeasts, which are stable under such treatments, and compare them with moderately resistant species and strains. In the current study, we investigated the resistance to dehydration-rehydration of six psychrotolerant yeast strains belonging to two species. All studied strains of Solicoccozyma terricola and Naganishia albida were found to be highly resistant to dehydration-rehydration. The viability of S. terricola strains was close to 100%. Such results have not been previously reported in studies of anhydrobiosis in yeasts. The plasma membrane changes, revealed by determining its permeability under various rehydration conditions, were also surprisingly minimal. Thus, the high level of resistance of psychrotolerant yeast strains might be related to the chemical composition and molecular organisation of their plasma membranes. Aside from plasma membrane characteristics, other important factors may also influence the maintenance of yeast cell viability under conditions of dehydration-rehydration.

Tardigrades are microscopic animals that enter an ametabolic state called anhydrobiosis when facing desiccation and can return to their original state when water is supplied. The genomic sequencing of microscopic animals such as tardigrades risks bacterial contamination that sometimes leads to erroneous interpretations, for example, regarding the extent of horizontal gene transfer in these animals. Here, we provide an ultralow input method to sequence the genome of the tardigrade, Hypsibius dujardini, from a single specimen. By employing rigorous washing and contaminant exclusion along with an efficient extraction of the 50 ~ 200 pg genomic DNA from a single individual, we constructed a library sequenced with a DNA sequencing instrument. These libraries were highly reproducible and unbiased, and an informatics analysis of the sequenced reads with other H. dujardini genomes showed a minimal amount of contamination. This method can be applied to unculturable tardigrades that could not be sequenced using previous methods.

The larvae of the African midge, Polypedilum vanderplanki, can enter an ametabolic state called anhydrobiosis to conquer fatal desiccation stress. The Pv11 cell line, derived from embryos of the midge, shows desiccation tolerance by pretreatment with trehalose before desiccation; they can resume proliferation after rehydration. To address the underlying molecular mechanisms, we desiccated Pv11 cells after pretreatment with the medium containing trehalose and induced proliferation by rehydration. We collected the cells at each before and after desiccation and rehydration step and performed CAGE-seq of mRNA of those cells. By analysing differentially expressed genes (DEGs) among the results of CAGE-seq, we detected 384 DEGs after trehalose treatment and 14 DEGs after rehydration. Hierarchical clustering of the identified DEGs indicated that rehydration returns their expression pattern to that in the control culture state. DEGs involved in various stress responses, detoxification of harmful chemicals, and regulation of oxidoreduction were upregulated by trehalose treatment. DEGs for rehydration supported that DNA repair is one of the potential mechanisms involves recovery. This study provided initial insight into the molecular mechanisms underlying the extreme desiccation tolerance of Pv11 cells with a potential for proliferation following rehydration.

Terrestrial tardigrades, commonly known as “water bears”, are part of a phylum of microscopic, aquatic invertebrates famous for cryptobiosis and space travel, but little is known about their modes of dispersal on Earth. Wind is assumed, but not truly demonstrated, to be the major method of global dispersal. Yet, some water bear distribution patterns cannot be explained by patterns of prevailing winds. Mammals and birds have been proposed as potential animal vectors. Importantly, most nearctic-neotropical migrant birds move north and south, with many crossing the equator, whereas prevailing winds move west to east or east to west but do not cross the equator. When multiplied by billions of birds over tens of millions of years, if the ectozoochory of tardigrades by birds is true then both regional and intercontinental patterns can be better explained. To test for the potential role of birds in tardigrade dispersal, the nests of 10 species for birds were examined. Seventy percent of nests were positive for tardigrades, demonstrating that some birds are in a position for transference. The carcasses of eight birds (six species) found dead from window strikes and a Sandhill Crane (Grus canadensis) found dead during routine surveys were also examined. Of the birds examined, 66% yielded tardigrades from two classes, three orders, and five species, including juveniles, adults, and eggs, suggesting that many bird species are potential vectors for many species of tardigrades. Our data support the hypothesis of avian-mediated long distance dispersal of tardigrades and provide evidence that further investigation is warranted.

The springtail Megaphorura arctica Tullberg 1876 is widespread in the arctic and subarctic regions where it can be abundant along beaches. This species survives winters using cryoprotective dehydration as a cold tolerance strategy during which it becomes drastically dehydrated. Several studies have investigated the physiological responses associated with water loss of M. arctica under exposure to freezing temperatures, but little is known of the dynamics of body water and hemolymph osmolality when subjected to gradually increasing drought stress at temperatures above the freezing point. Therefore, an experiment was conducted in which M. arctica was subjected to relative humidities (RH) decreasing from fully saturated conditions to ca. 89%RH over a period of 30 days. During the experiment water content of springtails decreased from about 3 to ca. 0.5mgmg(-1) dry weight. Alongside with water loss, trehalose concentrations increased from nearly nothing to 0.12mg mg(-1) dry weight, which contributed to an increase in hemolymph osmolality from ca. 250mOsm to at least 7Osm. All springtails survived water loss down to 0.7mgmg(-1) dry weight and hemolymph osmolality of ca. 4Osm, and about 60% of the springtails survived with only 0.5mg watermg(-1) dry weight and osmolality of ca. 7Osm.At this level of dehydration, Differential Scanning Calorimetry analysis showed that most, but not all, osmotically active water was lost. It is discussed that the extensive dehydration must be associated with high concentrations of salts potentially causing denaturation and precipitation of cellular proteins. M. arctica is remarkably tolerant of dehydration, but because it does not endure loss of the osmotically inactive water it cannot be categorized as a truly anhydrobiotic species.

This review compares the molecular strategies employed by anhydrobiotic invertebrates to survive extreme water stress. Intrinsically disordered proteins (IDPs) play a central role in desiccation tolerance in all species investigated. Various hypotheses about the functions of anhydrobiosis-related intrinsically disordered (ARID) proteins, including late embryogenesis abundant (LEA) and tardigrade-specific intrinsically disordered proteins, are evaluated by broad sequence characterization. A surprisingly wide range in sequence characteristics, including hydropathy and the frequency and distribution of charges, is discovered. Interestingly, two clusters of similar proteins are found that potentially correlate with distinct functions. This may indicate two broad groups of ARID proteins, composed of one group that folds into functional conformations during desiccation and a second group that potentially displays functions in the hydrated state. A broad range of physiochemical properties suggest that folding may be induced by factors such as hydration level, molecular crowding, and interactions with binding partners. This plasticity may be required to fine-tune the ARID-proteome response at different hydration levels during desiccation. Furthermore, the sequence properties of some LEA proteins share qualities with IDPs known to undergo liquid-liquid phase separations during environmental challenges.

Two recent papers highlight the fascinating comparative genomics of anhydrobiosis, the ability to withstand complete desiccation, in bdelloid rotifers and tardigrades. However, both groups had to openly deal with the significant difficulties of generating and interpreting short-read draft assemblies—especially challenging in microscopic species with high sequence polymorphism. These exemplars demonstrate the need to go beyond single draft-quality reference genomes to high-quality multiple species comparative genomics if we are to fully capture the value of genomics.

Three issues are critical for successful cryopreservation of multicellular material: gases dissolved in liquid, thermal conductivity of the tissue, and localization of microstructures. Here we show that heat distribution is controlled by the gas amount dissolved in liquids and that when changing the liquid into solid, the dissolved gases either form bubbles due to the absence of space in the lattice of solids and/or are migrated toward the concentrated salt and sugar solution at the cost of amount of heat required to be removed to complete a solid-state transition. These factors affect the heat distribution in the organs to be cryopreserved. We show that the gas concentration issue controls fracturing of ice when freezing. There are volumetric changes not only when changing the liquid into solid (volume increases) but also reduction of the volume when reaching lower temperatures (volume decreases). We discuss these issues parallel with observations of the cryosurvivability of multicellular organisms, tardigrades, and discuss their analogy for cryopreservation of large organs.

This study focuses on the CO 2 -tolerance of soil nematodes from natural CO 2 springs (mofette fields). In laboratory experiments, we compared survival, reproduction, activity and reactivation of a CO 2 -sensitive species with a CO 2 -tolerant species. Both species survived even 100% CO 2 , but in an inactive state. The higher the CO 2 concentration the more individuals entered inactivity. We found significant differences between the two species: more adults of the CO 2 -tolerant species maintained activity and reproduction at higher CO 2 concentrations. Moreover, reactivation after inactivity was faster. Together with a higher juvenile mortality of the CO 2 -sensitive species, these interspecific differences are conclusive to explain the niche separation of the two species that was observed in the mofette field.

Anhydrobiosis is an adaptive strategy of certain organisms or specialised propagules to survive in the absence of water while programmed cell death (PCD) is a finely tuned cellular process of the selective elimination of targeted cell during developmental programme and perturbed biotic and abiotic conditions. Particularly during water stress both the strategies serve single purpose i.e., survival indicating PCD may also function as an adaptive process under certain conditions. During stress conditions PCD cause targeted cells death in order to keep the homeostatic balance required for the organism survival, whereas anhydrobiosis suspends cellular metabolic functions mimicking a state similar to death until reestablishment of the favourable conditions. Anhydrobiosis is commonly observed among organisms that have ability to revive their metabolism on rehydration after removal of all or almost all cellular water without damage. This feature is widely represented in terrestrial cyanobacteria and bryophytes where it is very common in both vegetative and reproductive stages of life-cycle. In the course of evolution, with the development of advanced vascular system in higher plants, anhydrobiosis was gradually lost from the vegetative phase of life-cycle. Though it is retained in resurrection plants that primarily belong to thallophytes and a small group of vascular angiosperm, it can be mostly found restricted in orthodox seeds of higher plants. On the contrary, PCD is a common process in all eukaryotes from unicellular to multicellular organisms including higher plants and mammals. In this review we discuss physiological and biochemical commonalities and differences between anhydrobiosis and PCD.

Diverse organisms capable of surviving desiccation, termed anhydrobiotes, include species from bacteria, yeast, plants, and invertebrates. However, most organisms are sensitive to desiccation, likely due to an assortment of different stresses such as protein misfolding and aggregation, hyperosmotic stress, membrane fracturing, and changes in cell volume and shape leading to an overcrowded cytoplasm and metabolic arrest. The exact stress(es) that cause lethality in desiccation-sensitive organisms and how the lethal stresses are mitigated in desiccation-tolerant organisms remain poorly understood. The presence of trehalose in anhydrobiotes has been strongly correlated with desiccation tolerance. In the yeast Saccharomyces cerevisiae, trehalose is essential for survival after long-term desiccation. Here, we establish that the elevation of intracellular trehalose in dividing yeast by its import from the media converts yeast from extreme desiccation sensitivity to a high level of desiccation tolerance. This trehalose-induced tolerance is independent of utilization of trehalose as an energy source, de novo synthesis of other stress effectors, or the metabolic effects of trehalose biosynthetic intermediates, indicating that a chemical property of trehalose is directly responsible for desiccation tolerance. Finally, we demonstrate that elevated intracellular maltose can also make dividing yeast tolerant to short-term desiccation, indicating that other disaccharides have stress effector activity. However, trehalose is much more effective than maltose at conferring tolerance to long-term desiccation. The effectiveness and sufficiency of trehalose as an antagonizer of desiccation-induced damage in yeast emphasizes its potential to confer desiccation tolerance to otherwise sensitive organisms.

Anhydrobiosis is a well-known phenomenon represented in a range of plant, animal and microbial taxa. It is a unique faculty of some organisms to survive in the absence of even traceable water in their cells. As water is essential for life and unequivocally important for all the biological reactions and molecular integrity of cellular components, surviving without water is nature’s toughest puzzle. Initial research in this direction to understand the overall mechanism and dynamics of cellular water was done several decades ago with primary focus on characterizing cellular water at different intensities of dehydration using biophysical tools that lead to the establishment (/development) of a correlation of water-binding ability of cell constituents with the extent of anhydrobiosis. Unfortunately, in due course, the research focus had gradually changed and lost this initial direction. We believe a precise characterization of cellular water during dehydrated conditions is still pertinent in the current era of multidisciplinary research. Here cellular water characterized employing biophysical tools can be very precisely correlated with ongoing metabolic activities and other molecular regulatory events that in turn help in characterizing anhydrobiosis. This review intends to revive earlier approaches that were used to characterize the state of cellular water. This could help modern research in anhydrobiosis to correlate ongoing molecular events and/or adaptations during any change in the hydration level very precisely with the particular state of cell water.

Accepted: 2015-03-18, 資料番号: SA1150128000

Polypedilum vanderplanki is a striking and unique example of an insect that can survive almost complete desiccation. Its genome and a set of dehydration-rehydration transcriptomes, together with the genome of Polypedilum nubifer (a congeneric desiccation-sensitive midge), were recently released. Here, using published and newly generated datasets reflecting detailed transcriptome changes during anhydrobiosis, as well as a developmental series, we show that the TCTAGAA DNA motif, which closely resembles the binding motif of the Drosophila melanogaster heat shock transcription activator (Hsf), is significantly enriched in the promoter regions of desiccation-induced genes in P. vanderplanki, such as genes encoding late embryogenesis abundant (LEA) proteins, thioredoxins, or trehalose metabolism-related genes, but not in P. nubifer Unlike P. nubifer, P. vanderplanki has double TCTAGAA sites upstream of the Hsf gene itself, which is probably responsible for the stronger activation of Hsf in P. vanderplanki during desiccation compared with P. nubifer To confirm the role of Hsf in desiccation-induced gene activation, we used the Pv11 cell line, derived from P. vanderplanki embryo. After preincubation with trehalose, Pv11 cells can enter anhydrobiosis and survive desiccation. We showed that Hsf knockdown suppresses trehalose-induced activation of multiple predicted Hsf targets (including P. vanderplanki-specific LEA protein genes) and reduces the desiccation survival rate of Pv11 cells fivefold. Thus, cooption of the heat shock regulatory system has been an important evolutionary mechanism for adaptation to desiccation in P. vanderplanki.

The aim of this project was to determine the metabolic rate of tardigrades and how it depends onconditions such as temperature and salinity, as well as how it changes during termination of the putativelyametabolic state of cryptobiosis and from this to discover novel insights into how tardigrade metabolismand the extraordinary abilities it facilitates may function. To this end, tardigrades were collected in Ölandand a method was developed for measuring their metabolic rate (nmol O2 · mg-1 · hour-1) using oxygenmicrosensors and microgradients. The metabolic rate of active Richtersius coronifers at 22 °C and a salinityof 0 ppt was 10.8 ± 1.84 (n = 28) and for dead specimens, it was 0.21 ± 0.03 (n = 4). For the Macrobiotusmacrocalix species, it was 13.4 ± 2.19 (n = 17). The metabolic rate of both species was found to beunaffected by scaling within the inherent size variation of the populations. The following metabolic rates(nmol O2 · mg-1 · hour-1) were also determined for R. coronifer at different temperatures and a salinity of0 ppt. 2 °C: 2.28 ± 0.48 (n = 8); 11 °C: 3.56 ± 0.59 (n = 6); 16 °C: 8.42 ± 0.82 (n = 6) and 33 °C: 19.5 ± 1.19 (n= 6). Q10-values were calculated to be ~ 1.5 in all temperature ranges – except from 11 – 16 °C where itwas ~ 5.5. This was concluded to be a range of relative temperature dependence (RRTD). The activationenergy of the rate-limiting step in the metabolic pathway was calculated to be 50.8 kJ/mole O2. At 22 °C,the metabolic rate increased with salinity from 0 – 4 ppt and decreased from 14 – 32 ppt. Survival rate was100 % at 0 – 4 ppt, 50 % at 14.4 ppt perchlorates and 0 % at 16 – 32 ppt NaCl. Plotting the metabolic rateover time revealed a spike to 286 % of the previous metabolic rate over 18 minutes for one tardigrade and180 % over 8 minutes for another during exposure to 14.4 ppt perchlorates. Both spikes occurred after 60minutes of exposure, where metabolic rate had been declining exponentially. The metabolic rate duringtermination of anhydrobiosis was determined for two R. coronifer tuns that successfully regained activityand 8 tuns that did not survive the process. For all 10 tuns, the metabolic rate was found to go throughthree distinct zones: heightened metabolic rate (~ 20 – 25 for successful tuns) with one or more local peaksfor less than one hour, followed by an exponential decrease as the tardigrades hydrated over the nextseveral hours and finally a period of low metabolic rate (~ 5 for successful tuns) that continued for morethan 24 hours after rehydration. The method allows precise determination of the oxygen consumption forindividual tardigrades and can be repurposed for a wide range of experimental set-ups – opening up a richfield of inquiry into the metabolism and energetics of tardigrade biology.

Survival in microhabitats that experience extreme fluctuations in water availability and temperature requires extreme adaptations. Antonie van Leeuwenhoek was the first who describe the phenomenon of the resurrection of a desiccated rotifer in 1702. As with some rotifers and other small organisms, tardigrades enter a desiccated state known as anhydrobiosis to withstand such environmental conditions. This allows them to cope with the temporal variation of available water and to extend their lifespan in an anhydrobiotic state by up to 20 years without biological aging, according to the Sleeping Beauty hypothesis. Heat shock proteins serve as molecular chaperones to preserve or restore protein integrity, and tardigrade-specific intrinsically disordered proteins (TDPs) as well as metabolite help prevent the formation of damaging cellular compartments aggregates during water stress.

A survey is presented about the early history of tardigrade research spanning the time from 1773, when the first description of a tardigrade was published by Goeze, until 1929, when the most comprehensive monographic approach by E. Marcus, unsurpassed today, was published. Almost from the beginning, two topics dominated “tardigradology”, i.e. phylogeny and systematics as well as cryptobiosis, especially anhydrobiosis, but also other issues (e.g. morphology, development and life history) have followed successfully with ongoing technical and preparatory improvements.