Search

Panagrolaimus namibiensis n. sp. was recovered and cultured from soils collected under Arthraerua leubnitziae (pencil-bush) in the Namib Desert of Namibia, one of the driest terrestrial habitats on Earth. It is described here based on morphometrics, scanning electron micrographs, light images, line drawings, and molecular data. The new species is distinguished by having a conspicuous posterior deirid, a hook-shaped stegostomal dorsal tooth, and anterior deirids and excretory pore aligned at mid-bulb. It was morphologically compared to eleven well-described species in the genus with which it shared similar labial structure (six distinct rounded lips, and low lip segments separated in pairs), conoid tail, and/or a lateral field with three incisures, including P. labiatus, P. kolymaensis, P. davidi, P. rigidus, and P. superbus. Bayesian phylogenetic analyses using SSU and LSU rDNA each placed P. namibiensis n. sp. within clades of Panagrolaimus species, although the two trees resolved its relationship to previously described species differently. Furthermore, our analyses showed the genus is not monophyletic. In a laboratory experiment, P. namibiensis n. sp. survived exposure to 0% relative humidity for 24 h, demonstrating the anhydrobiotic ability of this species that contributes to its survival in the Namib Desert.

Abstract Tardigrades are renowned for their ability to survive a wide array of environmental stressors. In particular, tardigrades can curl in on themselves while losing a significant proportion of their internal water content to form a structure referred to as a tun. In surviving varying conditions, tardigrades undergo distinct morphological transformations that could indicate different mechanisms of stress sensing and tolerance specific to the stress condition. Methods to effectively distinguish between morphological transformations, including between tuns induced by different stress conditions, are lacking. Herein, an approach for discriminating between tardigrade morphological states is developed and utilized to compare sucrose- and CaCl2-induced tuns, using the model species Hypsibius exemplaris. A novel approach of shadow imaging with confocal laser scanning microscopy enabled production of three-dimensional renderings of Hys. exemplaris in various physiological states resulting in volume measurements. Combining these measurements with qualitative morphological analysis using scanning electron microscopy revealed that sucrose- and CaCl2-induced tuns have distinct morphologies, including differences in the amount of water expelled during tun formation. Further, varying the concentration of the applied stressor did not affect the amount of water lost, pointing towards water expulsion by Hys. exemplaris being a controlled process that is adapted to the specific stressors.

Our ability to explore the cosmos by direct contact has been limited to a small number of lunar and interplanetary missions. However, the NASA Starlight program points a path forward to send small, relativistic spacecraft far outside our solar system via standoff directed-energy propulsion. These miniaturized spacecraft are capable of robotic exploration but can also transport seeds and organisms, marking a profound change in our ability to both characterize and expand the reach of known life. Here we explore the biological and technological challenges of interstellar space biology, focusing on radiation-tolerant microorganisms capable of cryptobiosis. Additionally, we discuss planetary protection concerns and other ethical considerations of sending life to the stars.

Tardigrada is an ecdysozoan lineage famed for its resilience. Tardigrades can tolerate high doses of radiation, low-oxygen environments, desiccation, and both high and low temperatures under a dormant state called "anhydrobiosis", which is a reversible halt of metabolism upon almost complete desiccation. A large amount of research has focused on the genetic pathways related to these capabilities, and a number of genes have been identified and linked to the extremotolerant response of tardigrades. However, the history of these genes is unclear, and the origins and history of extremotolerant genes within Tardigrada remain a mystery. Here, we generate the first phylogenies of six separate protein families linked with desiccation and radiation tolerance in Tardigrada: cytosolic abundant heat-soluble protein, mitochondrial abundant heat-soluble protein, secretory abundant heat-soluble protein, meiotic recombination 11 homolog, and the newly discovered Echiniscus testudo abundant heat-soluble proteins (alpha and beta). The high number of independent gene duplications found amongst the six gene families studied suggests that tardigrades have a complex history with numerous independent adaptations to cope with aridity within the limnoterrestrial environment. Our results suggest that tardigrades likely transitioned from a marine environment to a limnoterrestrial environment only twice, once in stem Eutardigrada and once in Heterotardigrada, which explains the unique adaptations to anhydrobiosis present in both classes. [ABSTRACT FROM AUTHOR]

To thrive in harsh environments, tardigrades have evolved the ability to enter the quiescent state of cryptobiosis, often characterized by transition into a so-called 'tun'. Here, we investigate osmobiosis, a substate of cryptobiosis induced by rising osmolyte concentrations. We follow the behaviour and morphology of Ramazzottius varieornatus during transfer from freshwater conditions into 3 Osmol/kg sucrose solution. The tardigrades easily survive the extreme change in external osmolality. During gradual exposure, they initiate tun formation at 0.2 Osmol/kg, with most specimens fully contracted into a tun at 0.5 Osmol/kg. The first transcriptomic profiling of osmobiotic tuns in comparison to active tardigrades reveals a modest shift, with 16% of the 3322 differentially expressed transcripts having a |log2 fold change| > 1. A gene ontology enrichment analysis shows enrichment within protein homeostasis and neurohormonal signalling, with a ubiquitin-conjugating enzyme and neurotransmitter receptor transcripts being down- and upregulated, respectively. A putative Hsp70 is upregulated, whereas transcripts related to eutardigrade-specific proteins, antioxidant defence and DNA repair show minor fold changes. Among putative membrane transporters, a monocarboxylate and two amino acid transporters are downregulated. Our findings are in agreement with previous studies in Ramazzottius indicating that cryptobiosis and tun formation involve no change or modest change in transcription. [ABSTRACT FROM AUTHOR]

Tardigrades are renowned for their ability to enter the extremotolerant state of latent life known as cryptobiosis. While it is widely accepted that cryptobiosis can be induced by freezing (cryobiosis) and by desiccation (anhydrobiosis), the latter involving formation of a so-called tun, the exact mechanisms underlying the state--as well as the significance of other cryptobiosis inducing factors--remain ambiguous. Here, we focus on osmotic and chemical stress tolerance in the marine tidal tardigrade Echiniscoides sigismundi. We show that E. sigismundi enters the tun state following exposure to saturated seawater and upon exposure to locality seawater containing the mitochondrial uncoupler DNP. The latter experiments provide evidence of osmobiosis and chemobiosis, i.e., cryptobiosis induced by high levels of osmolytes and toxicants, respectively. A small decrease in survival was observed following simultaneous exposure to DNP and saturated seawater indicating that the tardigrades may not be entirely ametabolic while in the osmobiotic tun. The tardigrades easily handle exposure to ultrapure water, but hypo-osmotic shock impairs tun formation and when exposed to ultrapure water the tardigrades do not tolerate DNP, indicating that tolerance towards dilute solutions involves energy-consuming processes. We discuss our data in relation to earlier and more contemporary studies on cryptobiosis and we argue that osmobiosis should be defined as a state of cryptobiosis induced by high external osmotic pressure. Our investigation supports the hypothesis that the mechanisms underlying osmobiosis and anhydrobiosis are overlapping and that osmobiosis likely represents the evolutionary forerunner of cryptobiosis forms that involve body water deprivation. [ABSTRACT FROM AUTHOR]

The article focuses on the ability of some animals and plants to respond to changing environmental conditions by temporarily suspending metabolic processes. In contemporary biology, this state between life and death is commonly labelled 'cryptobiosis', combining the Greek kryptos (hidden, concealed, secret) with biōsis (mode of life). I argue that the notion of 'cryptobiosis' does not account sufficiently for the processual and relational dimensions of ametabolic life. The article advances a related but different concept, which better addresses this liminal state of biological organisation: s uspended life. While cryptobiosis still nurtures the imaginary of some latent life, suspended life stresses the liminality of the neither-nor life and death. The notion also grasps the dynamic and ongoing transfer between the biological and the technological. While the debate on cryptobiosis has so far remained confined to the description of natural processes, suspended life (or limbiosis) promises to account for contemporary technological practices of cryopreservation. [ABSTRACT FROM AUTHOR]

Tardigrades are renowned for their ability to enter the extremotolerant state of latent life known as cryptobiosis. While it is widely accepted that cryptobiosis can be induced by freezing (cryobiosis) and by desiccation (anhydrobiosis), the latter involving formation of a so-called tun, the exact mechanisms underlying the state—as well as the significance of other cryptobiosis inducing factors—remain ambiguous. Here, we focus on osmotic and chemical stress tolerance in the marine tidal tardigrade Echiniscoides sigismundi. We show that E. sigismundi enters the tun state following exposure to saturated seawater and upon exposure to locality seawater containing the mitochondrial uncoupler DNP. The latter experiments provide evidence of osmobiosis and chemobiosis, i.e., cryptobiosis induced by high levels of osmolytes and toxicants, respectively. A small decrease in survival was observed following simultaneous exposure to DNP and saturated seawater indicating that the tardigrades may not be entirely ametabolic while in the osmobiotic tun. The tardigrades easily handle exposure to ultrapure water, but hypo-osmotic shock impairs tun formation and when exposed to ultrapure water the tardigrades do not tolerate DNP, indicating that tolerance towards dilute solutions involves energy-consuming processes. We discuss our data in relation to earlier and more contemporary studies on cryptobiosis and we argue that osmobiosis should be defined as a state of cryptobiosis induced by high external osmotic pressure. Our investigation supports the hypothesis that the mechanisms underlying osmobiosis and anhydrobiosis are overlapping and that osmobiosis likely represents the evolutionary forerunner of cryptobiosis forms that involve body water deprivation.

Lineage-specific genes can contribute to the emergence and evolution of novel traits and adaptations. Tardigrades are animals that have adapted to tolerate extreme conditions by undergoing a form of cryptobiosis called anhydrobiosis, a physical transformation to an inactive desiccated state. While studies to understand the genetics underlying the interspecies diversity in anhydrobiotic transitions have identified tardigrade-specific genes and family expansions involved in this process, the contributions of species-specific genes to the variation in tardigrade development and cryptobiosis are less clear. We used previously published transcriptomes throughout development and anhydrobiosis (5 embryonic stages, 7 juvenile stages, active adults, and tun adults) to assess the transcriptional biases of different classes of genes between 2 tardigrade species, Hypsibius exemplaris and Ramazzottius varieornatus. We also used the transcriptomes of 2 other tardigrades, Echiniscoides sigismundi and Richtersius coronifer, and data from 3 non-tardigrade species (Adenita vaga, Drosophila melanogaster, and Caenorhabditis elegans) to help identify lineage-specific genes. We found that lineage-specific genes have generally low and narrow expression but are enriched among biased genes in different stages of development depending on the species. Biased genes tend to be specific to early and late development, but there is little overlap in functional enrichment of biased genes between species. Gene expansions in the 2 tardigrades also involve families with different functions despite homologous genes being expressed during anhydrobiosis in both species. Our results demonstrate the interspecific variation in transcriptional contributions and biases of lineage-specific genes during development and anhydrobiosis in 2 tardigrades. [ABSTRACT FROM AUTHOR]

Tardigrades are microscopic animals that survive a remarkable array of stresses, including desiccation. How tardigrades survive desiccation has remained a mystery for more than 250 years. Trehalose, a disaccharide essential for several organisms to survive drying, is detected at low levels or not at all in some tardigrade species, indicating that tardigrades possess potentially novel mechanisms for surviving desiccation. Here we show that tardigrade-specific intrinsically disordered proteins (TDPs) are essential for desiccation tolerance. TDP genes are constitutively expressed at high levels or induced during desiccation in multiple tardigrade species. TDPs are required for tardigrade desiccation tolerance, and these genes are sufficient to increase desiccation tolerance when expressed in heterologous systems. TDPs form non-crystalline amorphous solids (vitrify) upon desiccation, and this vitrified state mirrors their protective capabilities. Our study identifies TDPs as functional mediators of tardigrade desiccation tolerance, expanding our knowledge of the roles and diversity of disordered proteins involved in stress tolerance.

Now there is a huge variety of scenarios of prebiotic chemical evolution, culminating in the emergence of life on Earth, which demonstrates the obvious insufficiency of existing criteria for a reliable consideration of this process. This article develops the concept of thermodynamic inversion (TI concept) according to which the real succession of the formation of metabolism during the origin of life is fixed in the stages of the exit of a resting bacterial cell from anabiosis (suspended animation), just as the succession of events of phylogenesis is fixed in ontogenesis. The deepest phase of anabiosis considers by us as an intermediate state of a microorganism between non-life and life: it is no longer able to counteract the increase in entropy, but retains structural memory of the previous living state. According to the TI concept, the intermediate state between non-life and life thermodynamically corresponds to the approximate equality of the total contributions of entropy and free energy in prebiotic systems (Sc x FEc). Considering such intermediate state in prebiotic systems and microorganisms as a starting point, the authors use the experimentally recorded stages of restoring the metabolic process when a resting (dormant) bacterial cell emerges from anabiosis as a guideline for identifying the sequence of metabolism origin in prebiotic systems. According to the TI concept, life originated in a pulsating updraft of hydrothermal fluid. It included four stages. 1) Self-assembly of a cluster of organic microsystems (complex liposomes). 2) Activation (formation of protocells): appearance in the microsystems a weak energy-giving process of respiration due to redox reactions; local watering in the membrane. 3) Initiation (formation of living subcells): formation of a non-enzymatic antioxidant system; dawning of the protein-synthesizing apparatus. 4) Growth (formation of living cells--progenotes): arising of the growth cell cycle; formation of the genetic apparatus. [ABSTRACT FROM AUTHOR]

Developing tumor-specific drug delivery systems with minimized off-target cargo leakage remains an enduring challenge. In this study, inspired from the natural cryptobiosis explored by certain organisms and stimuli-responsive polyphenol‒metal coordination chemistry, doxorubicin (DOX)-conjugated gelatin nanoparticles with protective shells formed by complex of tannic acid and FeIII (DG@TA-FeIII NPs) were successfully developed as an “AND” logic gate platform for tumor-targeted DOX delivery. Moreover, benefiting from the well-reported photothermal conversion ability of TA-FeIII complex, a synergistic tumor inhibition effect was confirmed by treating 4T1 tumor-bearing mice with DG@TA-FeIII NPs and localized near-infrared (NIR) laser irradiation. As a proof of concept study, this work present a simple strategy for developing “AND” logic gate platforms by coating enzyme-degradable drug conjugates with detachable polyphenol‒metal shells.

Group 1 (Dur-19, PF00477, LEA_5) Late Embryogenesis Abundant (LEA) proteins are present in organisms from all three domains of life, Archaea, Bacteria, and Eukarya. Surprisingly, Artemia is the only genus known to include animals that express group 1 LEA proteins in their desiccation-tolerant life-history stages. Bioinformatics analysis of circular dichroism data indicates that the group 1 LEA protein AfLEA1 is surprisingly ordered in the hydrated state and undergoes during desiccation one of the most pronounced disorder-to-order transitions described for LEA proteins from A. franciscana. The secondary structure in the hydrated state is dominated by random coils (42%) and β-sheets (35%) but converts to predominately α-helices (85%) when desiccated. Interestingly, AfLEA1 interacts with other proteins and nucleic acids, and RNA promotes liquid–liquid phase separation (LLPS) of the protein from the solvent during dehydration in vitro. Furthermore, AfLEA1 protects the enzyme lactate dehydrogenase (LDH) during desiccation but does not aid in restoring LDH activity after desiccation-induced inactivation. Ectopically expressed in D. melanogaster Kc167 cells, AfLEA1 localizes predominantly to the cytosol and increases the cytosolic viscosity during desiccation compared to untransfected control cells. Furthermore, the protein formed small biomolecular condensates in the cytoplasm of about 38% of Kc167 cells. These findings provide additional evidence for the hypothesis that the formation of biomolecular condensates to promote water stress tolerance during anhydrobiosis may be a shared feature across several groups of LEA proteins that display LLPS behaviors. [ABSTRACT FROM AUTHOR]

In this study, structural adaptations of the desiccation-resistant homosporous fern Ceterach officinarum Willd are revealed at the organ and cellular-tissue levels. The largest role is played by features that contribute to the maintenance of cell hydration. Xero-heliomorphic signs at the organ level are nanism, area reduction, and leatheriness of fronds and dense cover of trichomes and scales. At the cellular-tissue level, water is retained due to the relatively thick blade of fronds, their small cells, large number of cells per unit area and pycnomorphy, high values of the specific surface density of the fronds (SSDF), dorsiventrality of the mesophyll, and a relatively dense network of veins per unit area of the frond. At the biochemical and functional level, it is done by increasing the concentration of osmotically active substances, lowering osmotic pressure, and the accumulation of water-retaining chemical compounds (catechins and tannins); at the phytocenotic level it is due to facultative bryophily. Sciomorphic features at the cellular-tissue level are hypostomaticity, a relatively small number of stomata per unit area of frond, tortuous seams of epidermal cells, and minimal values of the ratio of cell surface to volume. Mesomorphic features are the differentiation of the mesophyll into columnar and spongy tissue, a thin cuticle layer on the surface of the epidermis, and the presence of stomata in the lower epidermis. Another adaptation mechanism that determines the rhythm of fern development is the ability to inactivate life processes and fall into cryptobiosis under conditions of water stress and high temperatures. Unlike poikilohydric ectohydric bryophytes, the sporophytes of this fern, resistant to dehydration, can withstand drying out (and are, to this extent, poikilohydric), but are endohydric. In short, the poikilohydricity of fern sporophytes is achieved on a different structural basis, which is more evolutionarily advanced in comparison with thalloid plants. However, the frequent state of cryptobiosis, especially under conditions of alternating wet and long dry seasons, leads to an imbalance in carbon metabolism. Apparently, poikilohydricity is not the most perfected and productive way to combat drought. [ABSTRACT FROM AUTHOR]

The recent discovery of an upper limit in the tolerance of an extremotolerant tardigrade to high temperatures is astounding. Although these microinvertebrates are able to endure severe environmental conditions, including desiccation, freezing and high levels of radiation, high temperatures seem to be an Achilles’ heel for active tardigrades. Moreover, exposure-time appears to be a limiting factor for the heat stress tolerance of the otherwise highly resilient desiccated (anhydrobiotic) tardigrades. Indeed, the survival rate of desiccated tardigrades exposed to high temperatures for 24 hours is significantly lower than for exposures of only 1 hour. Here, we investigate the effect of 1 week of high temperature exposures on desiccated tardigrades with the aim of elucidating whether exposure-times longer than 24 hours decrease survival even further. From our analyses we estimate a significant decrease in the 50% mortality temperature from 63ºC to 56ºC for Ramazzottius varieornatus exposed to high temperatures in the desiccated tun state for 24 hours and 1 week, respectively. This negative correlation between exposure-time and tolerance to high temperatures probably results from the interference of intracellular temperature with the homeostasis of macromolecules. We hypothesize that high temperatures denature molecules that play a vital role in sustaining and protecting the anhydrobiotic state.

Developing tumor-specific drug delivery systems with minimized off-target cargo leakage remains an enduring challenge. In this study, inspired from the natural cryptobiosis explored by certain organisms and stimuli-responsive polyphenol‒metal coordination chemistry, doxorubicin (DOX)-conjugated gelatin nanoparticles with protective shells formed by complex of tannic acid and FeIII (DG@TA-FeIII NPs) were successfully developed as an "AND" logic gate platform for tumor-targeted DOX delivery. Moreover, benefiting from the well-reported photothermal conversion ability of TA-FeIII complex, a synergistic tumor inhibition effect was confirmed by treating 4T1 tumor-bearing mice with DG@TA-FeIII NPs and localized near-infrared (NIR) laser irradiation. As a proof of concept study, this work present a simple strategy for developing "AND" logic gate platforms by coating enzyme-degradable drug conjugates with detachable polyphenol‒metal shells. An "AND" logic gate platform for controlled drug delivery was successfully developed by coating enzyme-degradable drug conjugates with detachable polyphenol-metal shells to mimic natural cryptobiosis. Image 1 [ABSTRACT FROM AUTHOR]

Copyright of Bulletin de la Societe Vaudoise des Sciences Naturelles is the property of Societe Vaudoise des Sciences Naturelles and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The recent discovery of an upper limit in the tolerance of an extremotolerant tardigrade to high temperatures is astounding. Although these microinvertebrates are able to endure severe environmental conditions, including desiccation, freezing and high levels of radiation, high temperatures seem to be an Achilles' heel for active tardigrades. Moreover, exposure-time appears to be a limiting factor for the heat stress tolerance of the otherwise highly resilient desiccated (anhydrobiotic) tardigrades. Indeed, the survival rate of desiccated tardigrades exposed to high temperatures for 24 hours is significantly lower than for exposures of only 1 hour. Here, we investigate the effect of 1 week of high temperature exposures on desiccated tardigrades with the aim of elucidating whether exposure-times longer than 24 hours decrease survival even further. From our analyses we estimate a significant decrease in the 50% mortality temperature from 63ºC to 56ºC for Ramazzottius varieornatus exposed to high temperatures in the desiccated tun state for 24 hours and 1 week, respectively. This negative correlation between exposure-time and tolerance to high temperatures probably results from the interference of intracellular temperature with the homeostasis of macromolecules. We hypothesize that high temperatures denature molecules that play a vital role in sustaining and protecting the anhydrobiotic state. [ABSTRACT FROM AUTHOR]

Proteinaceous liquid-liquid phase separation (LLPS) occurs when a polypeptide coalesces into a dense phase to form a liquid droplet (i.e., condensate) in aqueous solution. In vivo, functional proteinbased condensates are often referred to as membraneless organelles (MLOs), which have roles in cellular processes ranging from stress responses to regulation of gene expression. Late embryogenesis abundant (LEA) proteins containing seed maturation protein domains (SMP; PF04927) have been linked to storage tolerance of orthodox seeds. Themechanism by which anhydrobiotic longevity is improved is unknown. Interestingly, the brine shrimp Artemia franciscana is the only animal known to express such a protein (AfrLEA6) in its anhydrobiotic embryos. Ectopic expression of AfrLEA6 (AWM11684) in insect cells improves their desiccation tolerance and a fraction of the protein is sequestered into MLOs, while aqueous AfrLEA6 raises the viscosity of the cytoplasm. LLPS of AfrLEA6 is driven by the SMP domain, while the size of formed MLOs is regulated by a domain predicted to engage in protein binding. AfrLEA6 condensates formed in vitro selectively incorporate target proteins based on their surface charge, while cytoplasmic MLOs formed in AfrLEA6-transfected insect cells behave like stress granules. We suggest that AfrLEA6 promotes desiccation tolerance by engaging in two distinct molecular mechanisms: by raising cytoplasmic viscosity at even modest levels of water loss to promote cell integrity during drying and by forming condensates that may act as protective compartments for desiccation-sensitive proteins. Identifying and understanding the molecular mechanisms that govern anhydrobiosis will lead to significant advancements in preserving biological samples. [ABSTRACT FROM AUTHOR]

All organisms encounter abiotic stress but only certain organisms are able to cope with extreme conditions and enter into cryptobiosis (hidden life). Previously, we have shown that C. elegans dauer larvae can survive severe desiccation (anhydrobiosis), a specific form of cryptobiosis. Entry into anhydrobiosis is preceded by activation of a set of biochemical pathways by exposure to mild desiccation. This process called preconditioning induces elevation of trehalose, intrinsically disordered proteins, polyamines and some other pathways that allow the preservation of cellular functionality in the absence of water. Here, we demonstrate that another stress factor, high osmolarity, activates similar biochemical pathways. The larvae that acquired resistance to high osmotic pressure can also withstand desiccation. In addition, high osmolarity significantly increases the biosynthesis of glycerol making larva tolerant to freezing. Thus, to survive abiotic stress, C. elegans activates a combination of genetic and biochemical pathways that serve as a general survival program. [ABSTRACT FROM AUTHOR]

To persist in extreme environments, some meiofaunal taxa have adopted outstanding resistance strategies. Recent years have seen increased enthusiasm for understanding extreme-resistance mechanisms evolved by tardigrades, nematodes and rotifers, such as the capability to tolerate complete desiccation and freezing by entering a state of reversible suspension of metabolism called anhydrobiosis and cryobiosis, respectively. In contrast, the less common phenomenon of diapause, which includes encystment and cyclomorphosis, is defined by a suspension of growth and development with a reduction in metabolic activity induced by stressful environmental conditions. Because of their unique resistance, tardigrades and rotifers have been proposed as model organisms in the fields of exobiology and space research. They are also increasingly considered in medical research with the hope that their resistance mechanisms could be used to improve the tolerance of human cells to extreme stress. This review will analyse the dormancy strategies in tardigrades, rotifers and nematodes with emphasis on mechanisms of extreme stress tolerance to identify convergent and unique strategies occurring in these distinct groups. We also examine the ecological and evolutionary consequences of extreme tolerance by summarizing recent advances in this field. [ABSTRACT FROM AUTHOR]

Studies on the long-term survival of animals often focus on the specific instance of survival of animals only, and descriptions of subsequent reproduction are generally not reported. In this study, we recorded the reproductive performance of the first-generation offspring of the resuscitated individual (SB-1) and the hatchling of the resuscitated egg (SB-3) of the Antarctic tardigrade, Acutuncus antarcticus , after being frozen for 30.5 years. By providing further detailed description of the reproduction of SB-1 and SB-3 after revival, and then comparing the reproductive performance with that of their first-generation offspring, the possible indications of the damage accrued during the long-term preservation in SB-1 and SB-3 were more specifically detected. Additionally, the DNA analysis revealed two distinctively different mitochondrial genetic sequences of A. antarcticus between the SB strains and the LSW strain. The observed differences in some of the reproductive parameters between the two genetic types suggested a possible relationship between the life-history traits and genetic type in the species A. antarcticus. Further experiments using the SB-1 and SB-3 strains reared for a long period to exclude the instant effect of preservation are expected to improve our understanding of the mechanisms underlying the long-term survival of animals. [ABSTRACT FROM AUTHOR]

Nematodes can enter cryptobiosis by dehydration as an adaptation to low-temperature environments and recover from cryptobiosis by rehydration after environmental improvement. In this work, the survival of Bursaphelenchusxylophilus third-stage dispersal juveniles was studied in response to low-temperature treatment. The average survival rates were 1.7% after −80 °C treatment for 30 d and 82.2% after −20 °C treatment for 30 d. The changes of water content and inorganic salt ions that occur in pine trees during winter gradually alter the osmotic pressure in the liquid environment to dehydrate B. xylophilus juveniles, resulting in improved survival after low-temperature treatment. The survival rate at −20 °C improved to 92.1% when the juveniles entered cryptobiosis by osmotic regulation. The results of this study demonstrate that B. xylophilus third-stage dispersal juveniles can resist low-temperature stress through cryptobiosis, providing the theoretical basis for the identification of areas potentially vulnerable to B. xylophilus in the mid-temperature and cold temperature zones of China.

Myxomycetes constitute a group within the Amoebozoa well known for their motile plasmodia and morphologically complex fruiting bodies. One obstacle hindering studies of myxomycete evolution is that their fossils are exceedingly rare, so evolutionary analyses of this supposedly ancient lineage of amoebozoans are restricted to extant taxa. Molecular data have significantly advanced myxomycete systematics, but the evolutionary history of individual lineages and their ecological adaptations remain unknown. Here, we report exquisitely preserved myxomycete sporocarps in amber from Myanmar, ca. 100 million years old, one of the few fossil myxomycetes, and the only definitive Mesozoic one. Six densely-arranged stalked sporocarps were engulfed in tree resin while young, with almost the entire spore mass still inside the sporotheca. All morphological features are indistinguishable from those of the modern, cosmopolitan genus Stemonitis, demonstrating that sporocarp morphology has been static since at least the mid-Cretaceous. The ability of myxomycetes to develop into dormant stages, which can last years, may account for the phenotypic stasis between living Stemonitis species and this fossil one, similar to the situation found in other organisms that have cryptobiosis. We also interpret Stemonitis morphological stasis as evidence of strong environmental selection favouring the maintenance of adaptations that promote wind dispersal. [ABSTRACT FROM AUTHOR]

The aim of the study was to improve and determine the degree of freshness of meat of snails of Helix genus after different technological processing by bacterioscopic method. Since there is no data in the modern scientific literature about the determination of indicators of safety and quality of meat of snails, in particular the freshness of meat of different species and different technological processes by bacterioscopic method, therefore the problem is relevant. The meat of snails of genus Helix has been used for the study, subspecies: Helix pomatia, Helix aspersa maxima and Helix aspersa muller. 30 samples of meat of snails of each species, bred in a snail farm of the Kyiv region were selected for the study. The research was conducted in the winter, when the snails were in anabiosis condition. The meat of snails was investigated after various technological processing: live, chilled and cooked and frozen. According to the results of the study, it was found that the meat of live snails was fresh for 2 days; doubtful freshness - from 3 days to 5 days; stale - in 7 days; freshly chilled meat of snails was fresh in 2 days including; doubtful freshness - from 3 to 6 days; stale - in 7 and 8 days; and cooked and chilled snails' meat was fresh after the storage for 6 months at a temperature of minus 18 °C. These data are stable and reliable, therefore, these indicators can be used in assessing the safety of snail meat under different processing conditions and after different storage periods. [ABSTRACT FROM AUTHOR]

The tardigrade Ramazzottius varieornatus has remarkable resilience to a range of environmental stresses. In this study, we have characterised two members of the small heat shock protein (sHSP) family in R. varieornatus, HSP20-3 and HSP20-6. These are the most highly upregulated sHSPs in response to a 24 h heat shock at 35 0 C of adult tardigrades with HSP20-3 being one of the most highly upregulated gene in the whole transcriptome. Both R. varieornatus sHSPs and the human sHSP, CRYAB (HSPB5), were produced recombinantly for comparative structure-function studies. HSP20-3 exhibited a superior chaperone activity than human CRYAB in a heat-induced protein aggregation assay. Both tardigrade sHSPs also formed larger oligomers than CRYAB as assessed by size exclusion chromatography and transmission electron microscopy of negatively stained samples. Whilst both HSP20-3 and HSP20-6 formed particles that were variable in size and larger than the particles formed by CRYAB, only HSP20-3 formed filament-like structures. The particles and filament-like structures formed by HSP20-3 appear inter-related as the filament-like structures often had particles located at their ends. Sequence analyses identified two unique features; an insertion in the middle region of the N-terminal domain (NTD) and preceding the critical-sequence identified in CRYAB, as well as a repeated QNTN-motif located in the C-terminal domain of HSP20-3. The NTD insertion is expected to affect protein-protein interactions and subunit oligomerisation. Removal of the repeated QNTN-motif abolished HSP20-3 chaperone activity and also affected the assembly of the filament-like structures. We discuss the potential contribution of HSP20-3 to protein condensate formation., Competing Interests: Declaration of Competing interest No competing interests., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Killifishes survive and persist in extreme environments by exploiting both aquatic and terrestrial habitats for egg deposition, and by adjusting the length of development to match availability of water to support larval growth and maturation. Annual killifishes persist in ephemeral bodies of water through the production of drought-tolerant embryos. Survival of the environmental stresses associated with their highly variable and seasonal habitat is supported by their ability to enter into at least two states of metabolic and developmental dormancy, diapause or quiescence. There are three stages of diapause in annual killifishes, one occurring prior to gastrulation, one about midway through development, and one in late pre-hatching embryos. Quiescence may occur at any developmental stage. In addition, delayed hatching is known to occur in close relatives of the annual killifishes, and may be superficially confused with pre-hatching diapause. These types of developmental delay are induced by different cues and serve different purposes in the life history of the species. Thus, it is likely that the molecular mechanisms that induce dormancy and support survival are unique in each case. It is imperative that we properly define these forms of developmental dormancy in our studies in order to put our results into the proper ecological and evolutionary context. Here the unique characteristics of these distinct categories of developmental delay are reviewed. Developmental Dynamics 246:858-866, 2017. © 2017 The Authors Developmental Dynamics published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists [ABSTRACT FROM AUTHOR]

Tun formation is an essential morphological adaptation for entering the anhydrobiotic state in tardigrades, but its internal structure has rarely been investigated. We present the structure and ultrastructure of organs and cells in desiccated Richtersius coronifer by transmission and scanning electron microscopy, confocal microscopy, and histochemical methods. A 3D reconstruction of the body organization of the tun stage is also presented. The tun formation during anhydrobiosis of tardigrades is a process of anterior-posterior body contraction, which relocates some organs such as the pharyngeal bulb. The cuticle is composed of epicuticle, intracuticle and procuticle; flocculent coat; and trilaminate layer. Moulting does not seem to restrict the tun formation, as evidenced from tardigrade tuns that were in the process of moulting. The storage cells of desiccated specimens filled up the free inner space and surrounded internal organs, such as the ovary and digestive system, which were contracted. All cells (epidermal cells, storage cells, ovary cells, cells of the digestive system) underwent shrinkage, and their cytoplasm was electron dense. Lipids and polysaccharides dominated among reserve material of storage cells, while the amount of protein was small. The basic morphology of specific cell types and organelles did not differ between active and anhydrobiotic R. coronifer. [ABSTRACT FROM AUTHOR]

To examine physiological adaptations to the two combined stressors O 2 deprivation and extreme CO 2 concentrations, we compared respiratory responses of two nematode species occurring in natural CO 2 springs. The minimum O 2 concentration allowing maintenance of respiration in both species was 0.0176 μmol O 2 ml −1 (corresponds to 1.4% O 2 in air). After exposure to anoxia, individuals resumed respiration immediately when O 2 was added, but on a lower level compared to control and without showing a respiratory overshoot. A species-specific response was found in respiration rate during 20% CO 2 : the more tolerant species maintained respiration rates, whereas the sensitive species showed a decreased respiration rate as low as after anoxia. The results indicate that during 20% CO 2 the sensitive species undergo a survival state. We conclude, that the ability to maintain respiration even under low oxygen and high CO 2 concentrations may allow the better adapted species to occupy an ecological niche in the field, where others cannot exist. [ABSTRACT FROM AUTHOR]