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Tardigrades are microscopic animals that survive desiccation by inducing biostasis. To survive drying tardigrades rely on intrinsically disordered CAHS proteins, which also function to prevent perturbations induced by drying in vitro and in heterologous systems. CAHS proteins have been shown to form gels both in vitro and in vivo, which has been speculated to be linked to their protective capacity. However, the sequence features and mechanisms underlying gel formation and the necessity of gelation for protection have not been demonstrated. Here we report a mechanism of fibrillization and gelation for CAHS D similar to that of intermediate filament assembly. We show that in vitro, gelation restricts molecular motion, immobilizing and protecting labile material from the harmful effects of drying. In vivo, we observe that CAHS D forms fibrillar networks during osmotic stress. Fibrillar networking of CAHS D improves survival of osmotically shocked cells. We observe two emergent properties associated with fibrillization; (i) prevention of cell volume change and (ii) reduction of metabolic activity during osmotic shock. We find that there is no significant correlation between maintenance of cell volume and survival, while there is a significant correlation between reduced metabolism and survival. Importantly, CAHS Ds fibrillar network formation is reversible and metabolic rates return to control levels after CAHS fibers are resolved. This work provides insights into how tardigrades induce reversible biostasis through the self-assembly of labile CAHS gels.

Antarctica is populated by a diverse array of terrestrial fauna that have successfully adapted to its extreme environmental conditions. The origins and diversity of the taxa have been of continuous interest to ecologists since their discovery. Early theory considered contemporary populations as descendants of recent arrivals; however, mounting molecular evidence points to firmly established indigenous taxa far earlier than the Last Glacial Maximum, thus indicating more ancient origins. Here we present insights into Antarctica's terrestrial invertebrates by synthesizing available phylogeographic studies. Molecular dating supports ancient origins for most indigenous taxa, including Acari (up to 100 million years ago; Ma), Collembola (21–11 Ma), Nematoda (~30 Ma), Tardigrada (> 1 Ma) and Chironomidae (> 49 Ma), while Rotifera appear to be more recent colonizers (~130 Ka). Subsequent population bottlenecks and rapid speciation have occurred with limited gene transfer between Continental and Maritime Antarctica, while repeated wind- or water-borne dispersal and colonization of contiguous regions during interglacial periods shaped current distributions. Greater knowledge of Antarctica's fauna will focus conservation efforts to ensure their persistence. [ABSTRACT FROM AUTHOR]

Tardigrada, the water bears, are microscopic animals with walking appendages that are members of Ecdysozoa, the clade of molting animals that also includes Nematoda (round worms), Nematomorpha (horsehair worms), Priapulida (penis worms), Kinorhyncha (mud dragons), Loricifera (loricated animals), Arthropoda (insects, spiders, centipedes, crustaceans, and their allies), and Onychophora (velvet worms). The phylogenetic relationships within Ecdysozoa are still unclear, with analyses of molecular and morphological data yielding incongruent results. Accounting for across-site compositional heterogeneity using mixture models that partition sites in frequency categories, CATegories (CAT)-based models, has been shown to improve fit in Bayesian analyses. However, CAT-based models such as CAT-Poisson or CAT-GTR (where CAT is combined with a General Time Reversible matrix to account for replacement rate heterogeneity) have proven difficult to implement in maximum likelihood. Here, we use CAT-posterior mean site frequencies (CAT-PMSF), a new method to export dataset-specific mixture models (CAT-Poisson and CAT-GTR) parameterized using Bayesian methods to maximum likelihood software. We developed new maximum likelihood-based model adequacy tests using parametric bootstrap and show that CAT-PMSF describes across-site compositional heterogeneity better than other across-site compositionally heterogeneous models currently implemented in maximum likelihood software. CAT-PMSF suggests that tardigrades are members of Panarthropoda, a lineage also including Arthropoda and Onychophora. Within Panarthropoda, our results favor Tardigrada as sister to Onychophora plus Arthropoda (the Lobopodia hypothesis). Our results illustrate the power of CAT-PMSF to model across-site compositionally heterogeneous datasets in the maximum likelihood framework and clarify the relationships between the Tardigrada and the Ecdysozoa. [ABSTRACT FROM AUTHOR]

Chilled water units using centrifugal compressors with gas bearings are an important research direction, but the necessary additional refrigerant circulation for gas bearings and motor cooling increases the design and operation difficulty, and therefore gas-suspended chiller units have few applications in the building sector. By establishing a system model based on energy, exergy, economic, and environmental analyses, this paper analyzes and compares the coefficient of performance (COP), exergy efficiency, power consumption, and economy of three refrigeration cycles under different operating conditions. The results showed that the system performance is insensitive to the supply pressure of gas bearings due to the relatively small mass flow rate. The enhanced gas-bearing-assisted vapor compression chilled water system (EGVC) demonstrated superior COP and exergy efficiency, and lower CO2 emissions compared with the gas-bearing-assisted vapor compression chilled water system (GVCW) and dual-economizer gas-bearing-assisted vapor compression chilled water system (DGVC) for the various evaporation temperatures and ambient temperatures. Regardless of the system, the total exergy loss of the system was mainly from the condenser, accounting for approximately 40% of the total. Both the economic cost and total equal warming impact (TEWI) values of the system decreased with the evaporation temperature but increased with the ambient temperature. Specifically, the EGVC showed slightly higher economic cost and lower TEWI values than other systems. The performance parameters of the system were sensitive to the evaporation temperature for the three systems. [ABSTRACT FROM AUTHOR]

Abstract Background Panarthropods, a major group of invertebrate animals comprised of arthropods, onychophorans, and tardigrades, are the only limb-bearing members of Ecdysozoa. The complexity and versatility of panarthropod paired limbs has prompted great interest in their development to better understand the formation of these structures and the genes involved in this process. However, studies of limb patterning and development are overwhelmingly focused on arthropods, followed by select work on onychophorans but almost entirely lacking for tardigrades. This model organism bias is inherently limited and precludes a comparative analysis of how panarthropod legs originated, have evolved, and the likely limb patterning genes present in the earliest panarthropod ancestors. In this study, we investigated tardigrade homologs of seven arthropod distal limb patterning genes (apterous, aristaless, BarH1, clawless, Lim1, rotund, and spineless) to better characterize tardigrade limb development in a comparative context. Results We detected homologs of all seven genes in the eutardigrade Hypsibius exemplaris and heterotardigrade Echiniscoides cf. sigismundi suggesting their conservation in both tardigrade lineages. Hybridization chain reaction experiments in H. exemplaris reveal a regionalized expression pattern for the genes aristaless, BarH1, clawless, rotund and spineless. Conclusion The observed regionalized expression of the distal limb patterning genes in H. exemplaris might reflect the external morphological features of tardigrade legs, such as the distal claws, sensory organs in the proximal region, and specific muscle attachment sites. The comparison between the expression of these limb patterning genes in H. exemplaris relative to other panarthropods suggests their conserved role in the last common panarthropod ancestor, such as establishing the distal limb end and the distribution of sensory structures. Our results support the hypothesis that tardigrade legs are homologous to the distal region of other panarthropod limbs, as suggested by previous work on the expression of leg gap genes in H. exemplaris.

Although molting is a defining feature of the most species-rich animal taxa—the Ecdysozoa, including arthropods, tardigrades, nematodes, and others 1,2 —its evolutionary background remains enigmatic. In pancrustaceans, such as insects and decapods, molting is regulated by the ecdysteroid (Ecd) hormone and its downstream cascade (Figure 1A, see also the text). 3,4,5 However, whether Ecd-dependent molting predates the emergence of the arthropods and represents an ancestral machinery in ecdysozoans remains unclear. For example, involvement of the Ecd hormone in molting regulation has been suggested only in some parasitic nematodes outside of arthropods, 6,7 and insect Ecd synthesis and receptor genes are lacking in some ecysozoan lineages (Figure S1A). 8,9,10 In this study, we investigated the role of Ecd in the molting process of the tardigrade Hypsibius exemplaris. We show that the endogenous Ecd level periodically increases during the molting cycle of H. exemplaris. The pulse treatment with exogenous Ecd induced molting, whereas an antagonist of the Ecd receptor suppressed the molting. Our spatial and temporal gene expression analysis revealed the putative regulatory organs and Ecd downstream cascades. We demonstrate that tardigrade molting is regulated by the Ecd hormone, supporting the ancestry of Ecd-dependent molting in panarthropods. Furthermore, we were able to identify the putative neural center of molting regulation in tardigrades. This region may be homologous to the neural center in the protocerebrum of pancrustaceans and represent an ancestral state of panarthropods. Together, our results suggest that Ecd-dependent molting evolved in the early-late Ediacaran, 22–76 million years earlier than previously suggested. 11 [Display omitted] • Tardigrade molting is triggered by a pulse increase of ecdysteroid (Ecd) titer • Identification of putative molting regulatory organs in tardigrades • Reconstruction of the ancestral state of Ecd-dependent molting in panarthropods Yamakawa and Hejnol show that tardigrade molting is regulated by the ecdysteroid hormone, which plays a master regulatory role in arthropod molting. The ancestry of ecdysteroid-dependent molting and its evolutionary history are elucidated in panarthropods. [ABSTRACT FROM AUTHOR]

ABSTRACT Aim Location Time Period Major Taxa Studied Methods Results Main Conclusions Tardigrades are important members of Antarctic metazoan communities with many endemic species. Major biogeographic patterns of Antarctic fauna have been identified, in particular regarding the zonation across the Gressitt line, dividing Continental and Peninsular Antarctica. Evidences suggest that Antarctic tardigrades follow this zonation too, but this has never been rigorously tested.Limnoterrestrial ecosystems of Antarctica.1950 to Present.Tardigrades.Records of tardigrades from Antarctica were collected and their taxonomy and coordinates harmonised. Alpha and Beta diversity measures were calculated and compared across different Antarctica biogeographic areas, in particular across the Gressitt line. Analyses were repeated at different spatial scales to ensure their robustness.Tardigrades communities are different both in terms of alpha and beta diversity across the Gressitt line. Results were consistent across the analyses at different spatial scales. Taxa richness was higher in the Antarctic Peninsula compared to the Continental Antarctica. Sampling effort had a substantial effect on the measured richness. Despite having a significant effect, Gressitt line side and biogeographic areas explained a low amount of variance.The presence of a different Tardigrade communities composition across the Gressitt line is supported, and a geographical structure is present also at smaller scales. This geographic structuring suggests local endemisms and calls for attention to eventual effects of climate change on tardigrades communities. Faunistic data on Antarctica is still far from being exhaustive and Linnean and Wallacean biodiversity shortfalls are the two most immediate issues to be solved to have a more reliable estimation of the true Antarctic tardigrades biodiversity. [ABSTRACT FROM AUTHOR]

The genus Fractonotus was erected on the basis of the peculiar appearance of the apophyses for the insertion of the stylet muscles on the buccal tube, and it has been attributed, together with the genus Microhypsibius, to the family Microhypsibiidae on the basis of the structure of the claws. A subsequent molecular investigation on Microhypsibius (18S and 28S rRNA) assigned the family Microhypsibiidae to the superfamily Hypsibioidea. Recently two other species, Isohypsibius gilvus and Calohypsibius verrucosus were transferred to Fractonotus and the latter was sequenced (18S and 28S rDNA, ITS-2), with the conclusion that the genus Fractonotus should be assigned to the family Isohypsibiidae, superfamily Isohypsibioidea. However, the transfer of I. gilvus and C. verrucosus to Fractonotus was incorrect. In fact, these two species definitely have claws of the Isohypsibius type, while Fractonotus caelatus, the type species of the genus, clearly has claws of the Microhypsibius type, in addition to other characters of the Hypsibioidea. Therefore, Fractonotus remains a monospecific genus in the Microhypsibiidae family, superfamily Hypsibioidea. The other two species belong to Isohypsibius or, if later confirmed by further morphological and new molecular data, to a new genus of Isohypsibiidae. [ABSTRACT FROM AUTHOR]

Using integrative taxonomy, we redescribe an eutardigrade Xerobiotus euxinus Pilato et al. 2011 based on material from the type locality and additional population from the Black Sea Biosphere Reserve in the south of Ukraine. Integrative redescription is based on morphological and morphometric data of animals and eggs from both phase contrast light microscopy (PCM), as well as, from scanning electron microscopy (SEM), and four DNA markers, three nuclear (18S rRNA, 28S rRNA, ITS-2) and one mitochondrial (COI). Originally, the species was described solely based on adults' morphology. The uncorrected genetic distances indicated that X. euxinus is the most similar to X. gretae with a p-distance value of COI fragment. Morphologically, X. euxinus differs from all Xerobiotus taxa mainly by the shape of claws on legs IV, but also by some other morphological and morphometrical characters of eggs and animals. [ABSTRACT FROM AUTHOR]

Tardigrades possess the ability to enter an almost completely dehydrated state, anhydrobiosis. The CAHS (cytosolic abundant heat‐soluble) protein family has been identified as one of the anhydrobiosis‐related proteins. In particular, CAHS3 protein from an anhydrobiotic tardigrade, Ramazzottius varieornatus, shows heat‐solubility and reversible condensation and is one of the most highly expressed among the CAHS paralogs. A recently developed tardigrade‐specific vector showed tissue‐specific expression of RvCAHS3 most pronounced in the epidermis in vivo, contrary to the idea that anhydrobiotic genes are uniformly expressed in all tardigrade cells. In this study, we investigated the regulation of RvCAHS3 gene expression through in vivo expression experiments using tardigrade vectors with a series of truncated upstream regions coupled with in silico analysis to identify the anhydrobiosis‐related genes that are expressed under the same regulatory system as RvCAHS3. As a result, the 300–350 bp region upstream of RvCAHS3 is critical for regulating gene expression in tardigrade vector experiments, and three motifs conserved between two species of anhydrobiotic tardigrades were identified within a 500 bp region directly upstream of RvCAHS3 start codon. These motifs, which have also been identified upstream of other CAHS genes, could be associated with the regulatory system of anhydrobiosis‐related genes in tardigrades. [ABSTRACT FROM AUTHOR]

Interactions between a host organism and its associated microbiota, including symbiotic bacteria, play a crucial role in host adaptation to changing environmental conditions. Antarctica provides a unique environment for the establishment and maintenance of symbiotic relationships. One of the most extensively studied symbiotic bacteria in invertebrates is Wolbachia pipientis, which is associated with a wide variety of invertebrates. Wolbachia is known for manipulating host reproduction and having obligate or facultative mutualistic relationships with various hosts. However, there is a lack of clear understanding of the prevalence of Wolbachia in terrestrial invertebrates in Antarctica. We present the outcomes of a literature search for information on the occurrence of Wolbachia in each of the major taxonomic groups of terrestrial invertebrates (Acari, Collembola, Diptera, Rotifera, Nematoda, Tardigrada). We also performed profiling of prokaryotes based on three marker genes and Kraken2 in available whole genome sequence data obtained from Antarctic invertebrate samples. We found no reports or molecular evidence of Wolbachia in these invertebrate groups in Antarctica. We discuss possible reasons underlying this apparent absence and suggest opportunities for more targeted future research to confirm bacteria's presence or absence. [ABSTRACT FROM AUTHOR]

Background: Azolla is a nature's gift and regenerates within 24 hours and has tremendous uses like supplementary feed to livestock. It is one of the most nutritive animal feeds and also can be used by livestock farming communities. Azolla has several times higher levels of crude protein than other forage crops and is also rich in minerals. The aim of the current study is to study growth in various water sources and their quality as supplementary feed to livestock. Methods: A study was conducted in a randomized block design (RBD) with five different treatments and replicated five times to minimize the error. The study was carried out to explore the yield and nutritive value of Azolla pinnata cultivated under different water sources like well water, river water, bore well water, sewage water and drainage water. The duration of the study was three years from Jan 2019 to March 2022. The silpauline plastic bed having dimensions 12 x 4 ft size was used. Every alternate day, the fresh Azolla was harvested and recorded the weight. Result: The pooled data for three years (2019 to 2022) showed a higher yield of 0.31 kg/day of fresh Azolla pinnata in Mula Mutha river water (T2) and 0.30 kg in well water (T1) and sewage water (T4) crude protein content was highest (28.07 %) in sewage water (T4). [ABSTRACT FROM AUTHOR]

Background: Panarthropods, a major group of invertebrate animals comprised of arthropods, onychophorans, and tardigrades, are the only limb-bearing members of Ecdysozoa. The complexity and versatility of panarthropod paired limbs has prompted great interest in their development to better understand the formation of these structures and the genes involved in this process. However, studies of limb patterning and development are overwhelmingly focused on arthropods, followed by select work on onychophorans but almost entirely lacking for tardigrades. This model organism bias is inherently limited and precludes a comparative analysis of how panarthropod legs originated, have evolved, and the likely limb patterning genes present in the earliest panarthropod ancestors. In this study, we investigated tardigrade homologs of seven arthropod distal limb patterning genes (apterous, aristaless, BarH1, clawless, Lim1, rotund, and spineless) to better characterize tardigrade limb development in a comparative context. Results: We detected homologs of all seven genes in the eutardigrade Hypsibius exemplaris and heterotardigrade Echiniscoides cf. sigismundi suggesting their conservation in both tardigrade lineages. Hybridization chain reaction experiments in H. exemplaris reveal a regionalized expression pattern for the genes aristaless, BarH1, clawless, rotund and spineless. Conclusion: The observed regionalized expression of the distal limb patterning genes in H. exemplaris might reflect the external morphological features of tardigrade legs, such as the distal claws, sensory organs in the proximal region, and specific muscle attachment sites. The comparison between the expression of these limb patterning genes in H. exemplaris relative to other panarthropods suggests their conserved role in the last common panarthropod ancestor, such as establishing the distal limb end and the distribution of sensory structures. Our results support the hypothesis that tardigrade legs are homologous to the distal region of other panarthropod limbs, as suggested by previous work on the expression of leg gap genes in H. exemplaris. [ABSTRACT FROM AUTHOR]

The purpose of this article is to begin a discussion of how Indigenous ontologies and practices might be brought to bear on water policy and management in Europe. Such a discussion represents an ironic historical shift in the sense that these ontologies and practices have survived and continue to evolve in countries that have been characterized by European colonization (i.e., Australia, Canada, US, New Zealand, countries of Africa and South America, and not excluding the Sámi people of northern Europe). Increasingly research and policy interest has been directed toward the inclusion of Indigenous knowledge and perspectives in water governance in some of these places, especially Australia, Canada, and New Zealand. Here, we ask whether they might be a source of inspiration for rethinking the water policy in Europe. We argue that certain elements of Indigenous water knowledge and practices can be drawn from to reform European water policy on the ontological premise that people are part of nature and based on establishing and nurturing moral and legal relationships between water and people based on principles of respect and reciprocity. [ABSTRACT FROM AUTHOR]

The phylogenetic position of the tardigrade species Grevenius annulatus was clarified using specimens from North‐West Russia. Molecular phylogenetic analysis revealed close affinity of this species with the family Isohypsibiidae. At the same time, its isolated position within this clade, supported by a set of unique morphological and biological characters, prompted the distinguishing of a new genus Cucumibius gen. nov. A new genus Chilibius gen. nov. was also established for Isohypsibius sculptus. We provide a detailed description of the ultrastructure of C. annulatus comb. nov. body cuticle. The newly discovered presence of a complex cuticle of the ‘heterotardigrade type’ in the superfamily Isohypsibioidea is discussed. [ABSTRACT FROM AUTHOR]

Tardigrade diversity and distribution are enigmatic in most parts of the globe, and only some European countries can boast of a relatively well-studied water bear fauna. However, even these suffer from the lack of genetic data, which would substantiate faunistic data and make biogeographic comparisons easier. Denmark has never been intensively and systematically researched in this regard, thus a citizen science sampling of cryptogams (mosses, liverworts, and lichens) was launched in spring 2023, aiming at a comprehensive biodiversity survey across this insular country. Nearly 700 samples were selected out of 8.000 sent to NHMD, based on the quality of samples, representativeness of various regions of Denmark, and the type of substrate to allow unravelling of potential ecological associations between tardigrades and cryptogams. Importantly, a large fraction of morphological identifications was backed up by DNA barcode data based on ITS-2 (1001 sequences), and in some cases also on COI (93 sequences) and ITS-1 (22 sequences) molecular markers, which are recognised DNA fragments used in species delimitation. We quadruple the number of known Danish limno-terrestrial tardigrade species (55 spp. reported in this paper vs. 14 spp. reported in literature so far, most of which were contentious due to the insufficient knowledge on tardigrade taxonomy), demonstrating the power of integrative taxonomy. No fewer than nine spp. are new to science. This is the first case where tardigrade fauna of an entire country is examined both from morphological and DNA barcoding data perspective. [ABSTRACT FROM AUTHOR]

This review synthesizes recent developments in the field of tardigrade biogeography, tracing back to the origins of Baas Becking's hypothesis that 'everything is everywhere but the environment selects' to the latest empirical studies that favour biogeographic structuring of these microinvertebrates. I recapitulate evidence for diverse means of meiofauna dispersal, focusing on the two principal mechanisms suggested for tardigrades: wind (aeolian dispersal/anemochory) and animals (zoochory). I argue that tardigrade species with relatively well-documented geographic distributions display climatic regionalization. The literature treating purportedly cosmopolitan tardigrades is critically scrutinized and evidence for strict cosmopolitanism is deemed insufficient. Due to the presence of numerous endemics restricted to mountains, elevational diversity gradients can be recognized at a local scale (for example, within a single biogeographic region). Finally, the tardigrade faunas of a given region should be likely regarded as part of a regionalized macrometazoan fauna containing a small fraction of widespread, ubiquitous species (called 'biogeographic noise' herein). [ABSTRACT FROM AUTHOR]

Aim: Glaciers cover considerable portion of land and host diverse life forms from single‐celled organisms to invertebrates. However, the determinants of diversity and community composition of these organisms remain underexplored. This study addresses the biogeography, population connectivity and dispersal of these organisms, especially critical in understanding during the rapid recession of glaciers and increased extinction risk for isolated populations. By reconstructing the Quaternary biogeographic history of Fontourion glacialis, a widespread in Northern Hemisphere glacier obligate species of Tardigrada, we aim to understand how populations of glacier‐dwelling metazoans receive immigrants, respond to disappearing glaciers and to what extent remaining glaciers can serve as refugia. Location: Glaciers across Svalbard, Scandinavia, Greenland and Iceland. Methods: We analysed mtDNA (COI gene) variability of 263 F. glacialis specimens collected across the distribution range. Phylogeographic and coalescent‐based approaches were used to detect population differentiation patterns, investigate most likely models of gene flow and test the influences of geographical and climatic factors on the distribution of F. glacialis genetic variants. Results: Our findings indicate that the distribution of F. glacialis genetic variants is primarily influenced by geographical rather than climatic factors. Populations exhibit a dispersal‐limited distribution pattern, influenced by geographical distance and local barriers, even between neighbouring glaciers. Significantly, the genetic structure within Scandinavia suggests the existence of "southern" glacial or low‐temperature refugia, where F. glacialis may have survived a period of extensive deglaciation during the Holocene climatic optimum (8–5 kyr ago). Main Conclusion: The study uncovers complex metapopulation structures in F. glacialis, with impacts of local barriers, population bottlenecks as well as historical ice sheet fluctuations. It suggests that such populations can endure extended periods of deglaciation, highlighting the resilience of glacial refugia. The study highlights the necessity of understanding the diversity and population structure of ice‐dwelling fauna in both spatial and temporal contexts. [ABSTRACT FROM AUTHOR]

In order to assess the suitability of water sources for human consumption, six water samples were taken from open wells and drinking bore wells in several selected regions in the Kalaburagi district of Karnataka state, India, from December 2020 to January 2022. The analysis found that the local water sources are contaminated. Total dissolved solids, total alkalinity, chloride, calcium, and magnesium levels in the water exceeded the permissible limits. The samples analysed for the presence of microbial contamination indicate a worrying scenario from the point of view of public health. As a result, such studies must be expanded to include open wells and bore wells in individual homes, as well as detailed investigations of the physicochemical and microbiological quality of drinking water sources in Kalaburagi district. [ABSTRACT FROM AUTHOR]

Tardigrades, the most resilient animals known to science, have survived several mass extinctions, flown into orbit and landed on the Moon. New research reveals details of their exceptional survival skills and how they evolved. Michael Gross reports. Tardigrades, the most resilient animals known to science, have survived several mass extinctions, flown into orbit and landed on the Moon. New research reveals details of their exceptional survival skills and how they evolved. [ABSTRACT FROM AUTHOR]

Tardigrades are a diverse phylum of microscopic invertebrates widely known for their extreme survival capabilities. Molecular clocks suggest that tardigrades diverged from other panarthropods before the Cambrian, but their fossil record is extremely sparse. Only the fossil tardigrades Milnesium swolenskyi (Late Cretaceous) and Paradoryphoribius chronocaribbeus (Miocene) have resolved taxonomic positions, restricting the availability of calibration points for estimating for the origin of this phylum. Here, we revise two crown-group tardigrades from Canadian Cretaceous-aged amber using confocal fluorescence microscopy, revealing critical morphological characters that resolve their taxonomic positions. Formal morphological redescription of Beorn leggi reveals that it features Hypsibius-type claws. We also describe Aerobius dactylus gen. et sp. nov. based on its unique combination of claw characters. Phylogenetic analyses indicate that Beo. leggi and Aer. dactylus belong to the eutardigrade superfamily Hypsibioidea, adding a critical fossil calibration point to investigate tardigrade origins. Our molecular clock estimates suggest an early Paleozoic diversification of crown-group Tardigrada and highlight the importance of Beo. leggi as a calibration point that directly impacts estimates of shallow nodes. Our results suggest that independent terrestrialization of eutardigrades and heterotardigrades occurred around the end-Carboniferous and Lower Jurassic, respectively. These estimates also provide minimum ages for convergent acquisition of cryptobiosis. The redescription of two Cretaceous-aged tardigrade fossils resolved their relationship with modern species, with one belonging to a new genus. This new information is critical for calibrating the timing of the evolutionary origins of tardigrades. [ABSTRACT FROM AUTHOR]

Marine birds and pinnipeds which come to land to breed, rest and moult are widely known to fertilize adjacent terrestrial ecosystems, with cascading effects on vegetation and other trophic levels. We provide a synthesis of the consequences of allochthonous nutrient enrichment for terrestrial invertebrate communities within and around marine vertebrate aggregation sites and nutrient sources in the High Arctic and Continental and Maritime Antarctic, the most nutrient-poor and environmentally extreme parts of the polar regions. Using a combination of literature review (identifying 19 articles from the Arctic Svalbard archipelago and 12 from different Antarctic locations) and new analyses of available datasets of springtail, mite and tardigrade community composition, we confirmed that terrestrial invertebrate abundance and species richness tended to increase, and their community compositions changed, as a result of marine vertebrate fertilisation in both polar regions. These changes were significantly greater on talus slopes enriched by kittiwakes, guillemots and little auks in the Arctic, as compared to the edges of penguin colonies in the Antarctic. Both these habitat areas were typically abundantly vegetated and provided the most favourable microhabitat conditions for terrestrial invertebrates. The most heavily disturbed and manured areas within Antarctic penguin rookeries and seal wallows, generally on flat or gently sloping ground, were typically characterised by extremely low invertebrate diversity. In the Arctic, only sites directly beneath densely-occupied bird cliffs were to some extent comparably barren. Invertebrate responses are dependent on a combination of vertebrate activity, local topography and vegetation development. [ABSTRACT FROM AUTHOR]

An important, but generally overlooked source in intraspecific variability of characters used in tardigrades taxonomy is sexual dimorphism. Dioecious tardigrades species with unisexual or bisexual populations are common, but external sexual dimorphism is rarely observed. The discovery and integrative analysis of a Diploechiniscus species population with high sexual dimorphism from Calvert Island (Canada) has allowed its description as a new species. Diploechiniscus dimorphus n. sp. is characterized by a different chaetotaxy in males and females, and by enlarged cephalic sensory appendages in the males. The discovery of this new species shows that it is important to consider sexual dimorphism as a source of intraspecific variability in tardigrade taxonomy due to its implications on the use of traits commonly used to delineate species such as chaetotaxy. Lastly, the finding of individuals of Diploechiniscus horningi (Schuster and Grigarick, 1971), a species previously synonymized with Diploechiniscus oihonnae (Richters, 1903), allows us to prove that it is genetically a separate species and to reinstate it. [ABSTRACT FROM AUTHOR]

Tardigrades are unique among animals in their resistance to dehydration, mainly due to anhydrobiosis and tun formation. They are also very resistant to high-energy radiation, low and high temperatures, low and high pressure, and various chemical agents, Interestingly, they are resistant to ionizing radiation both in the hydrated and dehydrated states to a similar extent. They are able to survive in the cosmic space. Apparently, many mechanisms contribute to the resistance of tardigrades to harmful factors, including the presence of trehalose (though not common to all tardigrades), heat shock proteins, late embryogenesis-abundant proteins, tardigrade-unique proteins, DNA repair proteins, proteins directly protecting DNA (Dsup and TDR1), and efficient antioxidant system. Antioxidant enzymes and small-molecular-weight antioxidants are an important element in the tardigrade resistance. The levels and activities of many antioxidant proteins is elevated by anhydrobiosis and UV radiation; one explanation for their induction during dehydration is provided by the theory of "preparation for oxidative stress", which occurs during rehydration. Genes coding for some antioxidant proteins are expanded in tardigrades; some genes (especially those coding for catalases) were hypothesized to be of bacterial origin, acquired by horizontal gene transfer. An interesting antioxidant protein found in tardigrades is the new Mn-dependent peroxidase. [ABSTRACT FROM AUTHOR]

Tardigrades (Tardigrada) are a phylum of micrometazoans found in all biomes on Earth, but their ecology and habitat preferences remain vastly understudied. Boreal peatlands include a diversity of habitat types and high structural heterogeneity that represents an interesting system to study some of the poorly known habitat preferences of tardigrades. Here, we investigate for the first time tardigrade communities in peatland mosses and the latter's potential associations with key environmental variables. We collected 116 moss samples from 13 sites representing different peatland types and management histories. We found that tardigrades are common and diverse in boreal peatlands, as tardigrades were present in 72% of the collected samples and we identified 14 tardigrade genera. Tardigrade abundance seemed to increase alongside the increasing tree basal area and the density was higher in the microtopographic level further from the water table level, that is, hummocks (mean 117/moss gram) than in lawns/hollows (mean 84/moss gram). Furthermore, the highest tardigrade density was found in the moss taxa that are associated with forested peatland types (i.e., feather mosses) (321 mean/moss gram). Finally, we found interesting patterns regarding tardigrade functional diversity, as carnivorous tardigrades were found only in peatlands with tree basal area > 20 m2 and mostly in hummocks. Our study demonstrates that the habitat heterogeneity of peatlands (e.g., variation in moisture and vegetation cover) represents an interesting system to study tardigrade ecology and habitat preferences. However, since we found variation in tardigrade abundance and communities across peatland types and microhabitats within peatlands, our results highlight that such studies should be conducted with numerous replicate samples and a systematic study design that properly addresses the habitat heterogeneity between and within different peatland types. [ABSTRACT FROM AUTHOR]

This is the first survey of marine tardigrades from the British Virgin Islands, though two species were previously reported from St. Croix, U.S. Virgin Islands. In June 2016, we collected subtidal and intertidal sand samples from various locations throughout the British Virgin Islands. We found 602 tardigrades in 18 of 21 samples, and these included 12 taxa, one of which, Batillipes wyedeleinorum sp. nov., is new to science and described here. We compared abundance and species diversity in intertidal and subtidal samples and found significantly greater abundance in intertidal habitats but no significant difference in the number of observed species between the two habitats. We calculated Chao 1 species richness, which indicated higher estimated richness in intertidal habitats and 15 ± 3.7 species (x̅ ± SD) in both habitats combined. Non-metric Multidimensional Scaling revealed differences in species composition between the two habitats with some species showing clear preferences for one or the other. [ABSTRACT FROM AUTHOR]

Recently, in 2023, WHO and UNICEF published a report on water, sanitation and hygiene (WASH) progress. Report highlighted that there is a need to increase WASH progress rate by 3 to 6 fold to achieve clean water and sanitation (SDG) 6 by 2030. Main aim of this research paper is to assess progress of WASH and identify risk factors which are yet barrier in attaining SDG 3 and SDG 6 in Bist Doab area of Punjab. Household survey was conducted to assess level of WASH in study region through well-structured questionnaire using multistage random purposive sampling. Village environmental conditions were also observed and included in the study to identify risk factor present for water - borne diseases. Survey revealed that level of WASH has improved in Punjab in drinking water sources, sanitation level and personal hygiene. In addition, survey disclosed people are not satisfied with quality of water supplied in their villages. Also, study found low awareness level among people regarding water borne diseases and presence of permanent water logged areas, improper waste disposal, open drainage are some favorable grounds for outbreak of water borne and other water associated diseases such as malaria and dengue. [ABSTRACT FROM AUTHOR]

Lobopodians represent a key step in the early history of ecdysozoans since they were the first animals to evolve legs within this clade. Their Cambrian representatives share a similar body plan with a typically cylindrical annulated trunk and a series of non-jointed legs. However, they do not form a monophyletic group and likely include ancestors of the three extant panarthropod lineages (Tardigrada, Onychophora, Euarthropoda). Some species display astonishing protective devices such as cuticular plates and spines. We describe here the armor and molting process of Microdictyon from the early Cambrian of China. Microdictyon secreted ovoid paired cuticular sclerites that were duplicated in a non-synchronous way along the animal's body. The reticulated pattern and cuticular architecture of these sclerites have similarities to extant armored tardigrades that recently served in hypothesizing that tardigrades are possibly miniaturized lobopodians. Ecdysis and hard cuticular protection are now well documented in the whole spectrum of early Cambrian ecdysozoans such as soft-bodied scalidophorans, lobopodians and fully articulated euarthropods. We hypothesize that the secretion of sclerotized cuticular elements periodically renewed via ecdysis was a key innovation that opened large-scale evolutionary opportunities to invertebrate animal life, specifically ecdysozoans, both in terms of anatomical functionalities and ecological success. This paper presents exceptionally preserved fossils from the early Cambrian that show how molting occurred in some of the very earliest arthropod relatives, a trait which enabled continuous growth in animals with hard exoskeletons. [ABSTRACT FROM AUTHOR]

Tardigrada is an ancient lineage of miniaturized animals. As an outgroup of the well‐studied Arthropoda and Onychophora, studies of tardigrades hold the potential to reveal important insights into body plan evolution in Panarthropoda. Previous studies have revealed interesting facets of tardigrade development and genomics that suggest that a highly compact body plan is a derived condition of this lineage, rather than it representing an ancestral state of Panarthropoda. This conclusion was based on studies of several species from Eutardigrada. We review these studies and expand on them by analyzing the publicly available genome and transcriptome assemblies of Echiniscus testudo, a representative of Heterotardigrada. These new analyses allow us to phylogenetically reconstruct important features of genome evolution in Tardigrada. We use available data from tardigrades to interrogate several recent models of body plan evolution in Panarthropoda. Although anterior segments of panarthropods are highly diverse in terms of anatomy and development, both within individuals and between species, we conclude that a simple one‐to‐one alignment of anterior segments across Panarthropoda is the best available model of segmental homology. In addition to providing important insight into body plan diversification within Panarthropoda, we speculate that studies of tardigrades may reveal generalizable pathways to miniaturization. [ABSTRACT FROM AUTHOR]

The current biodiversity of 14 phyla, namely Platyhelminthes, Xenacoelomorpha, Nematoda, Acanthocephala, Brachiopoda, Kinorhyncha, Nemertea, Chaetognatha, Tardigrada, Gastrotricha, Rotifera, Phoronida, Echinodermata, and Chordata (invertebrates only, including the subphyla Tunicata, Cephalochordata, and Hemichordata) from the coasts of Türkiye is revisited. It was found that a total number of 695 species occur along all the coastlines of Türkiye, with the Black Sea being represented by 297 species, the Sea of Marmara by 305 species, the Aegean Sea by 308 species, and the Levantine Sea by 204 species. The most species-rich phyla in these regions were Platyhelminthes (249 species), Nematoda (131), Echinodermata (98), and Chordata (85). A total of 26 alien species have been reported from the regions to date, of which one species belongs to Chaetognatha, 8 species to Echinodermata, and 17 species to Tunicata. The highest number of alien species (17) was encountered in the Levantine Sea and the lowest (2) was in the Black Sea. [ABSTRACT FROM AUTHOR]

Tardigrades are omnipresent microfauna with scarce record on their ecology in soils. Here, we investigated soil inhabiting tardigrade communities in five contrasting polar habitats, evaluating their abundance, diversity, species richness, and species composition. Moreover, we measured selected soil physico‐chemical properties to find the drivers of tardigrade distribution among these habitats. In spite of reported tardigrade viability in extreme conditions, glacier forelands represented a habitat almost devoid of tardigrades. Even dry and wet tundra with soil developing for over more than 10 000 years held low abundances compared to usual numbers of tardigrades in temperate habitats. Polar habitats also differ in species composition, with Diaforobiotus islandicus being typical species for dry and Hypsibius exemplaris for wet tundra. Overall, tardigrade abundance was affected by the content of nutrients as well as physical properties of soil, i.e. content of total nitrogen (TN), total organic carbon (TOC), stoniness, soil texture and the water holding capacity (WHC). While diversity and species composition were significantly related to soil physical properties such as the bulk density (BD), soil texture, stoniness, and WHC. Physical structure of environment was, therefore, an important predictor of tardigrade distribution in polar habitats. Since many studies failed to identify significant determinants of tardigrade distribution, we encourage scientists to include physical properties of tardigrade habitats as explanatory variables in their studies. [ABSTRACT FROM AUTHOR]

Seventeen species of Tardigrada were found in submerged mosses of 17 freshwater bodies from the SE part of the island of Hopen (Svalbard). Fourteen species are new records for Hopen; Pseudechiniscus islandicus was not previously reported from Svalbard. The most frequently and numerously encountered species were Isohypsibius granulifer, Hypsibius dujardini, Dactylobiotus dispar, Macrobiotus dianeae and Amphibolus weglarskae.

Molting is a key feature of Ecdysozoa, but little is known about the regulation of this process in most ecdysozoans. A new study demonstrates that molting is regulated by the ecdysteroid hormone in the tardigrade Hypsibius exemplaris. [ABSTRACT FROM AUTHOR]

Tardigrades are small aquatic invertebrates known for their remarkable tolerance to diverse extreme stresses. To elucidate the in vivo mechanisms underlying this extraordinary resilience, methods for genetically manipulating tardigrades have long been desired. Despite our prior success in somatic cell gene editing by microinjecting Cas9 ribonucleoproteins (RNPs) into the body cavity of tardigrades, the generation of gene-edited individuals remained elusive. In this study, employing an extremotolerant parthenogenetic tardigrade species, Ramazzottius varieornatus, we established conditions that led to the generation of gene-edited tardigrade individuals. Drawing inspiration from the direct parental CRISPR (DIPA-CRISPR) technique employed in several insects, we simply injected a concentrated Cas9 RNP solution into the body cavity of parental females shortly before their initial oviposition. This approach yielded gene-edited G0 progeny. Notably, only a single allele was predominantly detected at the target locus for each G0 individual, indicative of homozygous mutations. By co-injecting single-stranded oligodeoxynucleotides (ssODNs) with Cas9 RNPs, we achieved the generation of homozygously knocked-in G0 progeny, and these edited alleles were inherited by G1/G2 progeny. This is the first example of heritable gene editing in the entire phylum of Tardigrada. This establishment of a straightforward method for generating homozygous knockout/knock-in individuals not only facilitates in vivo analyses of the molecular mechanisms underpinning extreme tolerance, but also opens up avenues for exploring various topics, including Evo-Devo, in tardigrades. Author summary: Tardigrades, tiny aquatic invertebrates also known as water bears, are celebrated for their extraordinary resilience to various extreme stresses like dehydration, radiation, and unusual ranges of temperature and pressure. Understanding the molecular mechanisms of this resilience not only satisfies scientific curiosity but also holds promise for the development of innovative technologies for the dry preservation of biomaterials like biomedicines and vaccines. However, the lack of a heritable genome manipulation technology has hindered in vivo analyses of these mechanisms. This study addresses this longstanding challenge in the field. Employing an extremotolerant parthenogenetic tardigrade species, we established conditions that enable the efficient production of gene-manipulated individuals. Using these conditions, the simple injection of Cas9 genome-editing components into parental females leads to the generation of knockout/knock-in progeny. Unlike similar approaches in other animals, we obtained mutant progeny predominantly carrying a single type of mutation, namely, homozygous mutants, which significantly facilitates downstream analyses. This is the first report of a heritable gene-editing method in the entire group of tardigrades. The establishment of this straightforward method for generating gene-manipulated tardigrades not only facilitates in vivo analyses of the molecular mechanisms underpinning extreme tolerance, but also opens up avenues for exploring various topics, including Evo-Devo. [ABSTRACT FROM AUTHOR]

Tardigrades can survive hostile environments such as desiccation by adopting a state of anhydrobiosis. Numerous tardigrade species have been described thus far, and recent genome and transcriptome analyses revealed that several distinct strategies were employed to cope with harsh environments depending on the evolutionary lineages. Detailed analyses at the cellular and subcellular levels are essential to complete these data. In this work, we analyzed a tardigrade species that can withstand rapid dehydration, Ramazzottius varieornatus. Surprisingly, we noted an absence of the anhydrobiotic-specific extracellular structure previously described for the Hypsibius exemplaris species. Both Ramazzottius varieornatus and Hypsibius exemplaris belong to the same evolutionary class of Eutardigrada. Nevertheless, our observations reveal discrepancies in the anhydrobiotic structures correlated with the variation in the anhydrobiotic mechanisms. [ABSTRACT FROM AUTHOR]

Tardigrades, are a phylum of microscopic organisms well known for their resistance to extreme conditions thanks to adaptations such as cryptobiosis, in which they are able to suspend their metabolism until more favorable conditions arise. These organisms are found in a wide range of environments, and high Andean mountains are not the exception, even though weather conditions are highly variable during the day, let alone a month. An experiment was conducted at an altitude of 2600 m in Bogotá, Colombia, to evaluate the resistance of Macrobiotus sp. found on trees. Three sets of fifteen tardigrades were exposed to temperatures of 20 °C, 30 °C, and 40 °C, with a heating rate of 0.5 °C/min. The tardigrades were then examined to determine the number of living, dead, and "tun" organisms. At 20 °C, 22% of the individuals were dead; at 30 °C, 35.56% were dead; and at 40 °C, 46.67% were dead. No tardigrades were found in the "tun" state at any temperature. Therefore, the data show an increase in mortality as the temperature rises. However, considering the climatic conditions recorded, studied tardigrades are able to withstand higher temperatures than those they are usually exposed to. The lack of the "tun" state implies that high temperatures, at least at this rate, do not trigger this state, whereas conditions like desiccation might. More research is needed to explore this further. [ABSTRACT FROM AUTHOR]

In this paper we provide integrative description (morphological and genetic) of the new eutardigrade species Mesobiotus mandalorisp. nov. from central Poland, found during research on the vertical distribution of Tardigrada in the Czerniejewskie Forests. Mesobiotus mandalorisp. nov. belongs to the harmsworthi group, but it differs from the members of this group in some morphometric characters of the bucco-pharyngeal apparatus, claws and/or eggs. Morphologically, Meb. mandalorisp. nov. is most similar to Meb. pseudocoronatus, but it differs from it by a larger bare egg diameter and smaller number of egg processes on egg circumference. Morphometrical data were supported by results of comparative genetic analysis of four molecular markers: 18S rRNA, 28S rRNA, ITS2 and COI. According to COI the new species is most similar to Meb. skorackii with the genetic distance of 21.1%. [ABSTRACT FROM AUTHOR]

Species within the eutardigrade superfamily Macrobiotoidea are usually differentiated through their eggshell morphology. However, this trait can show very high intraspecific variability and, as consequence, species delimitation is challenging without molecular support. Although eggshell variability usually consists of small details, cases of species with very different egg morphotypes are known. Paramacrobiotus bifrons sp. nov. here described with an integrative approach, represents one of the species with extreme variability in eggshell morphology and it belongs to the areolatus group. The production by this gonochoric species of both areolatus-type and csotiensis-type eggs, the latter being rare in the group but most abundant in this species, was assessed by DNA barcoding, culturing, and inter-morphotype crosses. The reason underlying the production of two different eggshells resulted not related to tested culturing conditions, seasonality, or male's influence. Confocal (with and without staining), Light, and Scanning Electron Microscopies analyses of the two egg morphotypes laid by P. bifrons sp. nov. allowed to redescribe the csotiensis-type egg, shed light on its composition (excluding chitin as a component), and to find shared details supporting the belonging of the two egg morphotypes to the same species. [ABSTRACT FROM AUTHOR]

Moss samples were collected from trees and rocks in Haida Gwaii, British Columbia, Canada, and examined for the presence of tardigrades. Specimens from 24 taxa were found in 17 out of the 22 examined samples. New species records for British Columbia are provided and undescribed Grevenius and Crenubiotus species were found; a division in four morphogroups of Grevenius, based on number and presence of placoids, is provided to aid in the future identification. In addition, three specimens of a new species belonging to a potential new undescribed Diploechiniscus species were identified. The finding of Macrobiotus occidentalis occidentalis also provides the occasion to transfer the latter one to the genus Diaforobiotus, for which a new dichotomous key for the identification of its species is given and to redefine the family Richtersiusidae. The DNA sequences of selected taxa are also provided. The high number of tardigrade species collected from a relatively low number of samples highlight how still unexplored is tardigrade diversity, particularly in still-largely insular island systems like Haida Gwaii. [ABSTRACT FROM AUTHOR]

Microbiota are considered significant in the biology of tardigrades, yet their diversity and distribution remain largely unexplored. This is partly due to the methodological challenges associated with studying the microbiota of small organisms that inhabit microbe‐rich environments. In our study, we characterized the microbiota of 31 species of cultured tardigrades using 16S rRNA amplicon sequencing. We employed various sample preparation strategies and multiple types of controls and estimated the number of microbes in samples using synthetic DNA spike‐ins. We also reanalysed data from previous tardigrade microbiome studies. Our findings suggest that the microbial communities of cultured tardigrades are predominantly composed of bacterial genotypes originating from food, medium, or reagents. Despite numerous experiments, we found it challenging to identify strains that were enriched in certain tardigrades, which would have indicated likely symbiotic associations. Putative tardigrade‐associated microbes rarely constituted more than 20% of the datasets, although some matched symbionts identified in other studies. We also uncovered serious contamination issues in previous tardigrade microbiome studies, casting doubt on some of their conclusions. We concluded that tardigrades are not universally dependent on specialized microbes. Our work underscores the need for rigorous safeguards in studies of the microbiota of microscopic organisms and serves as a cautionary tale for studies involving samples with low microbiome abundance. [ABSTRACT FROM AUTHOR]

The present study is conducted to assess the radiological and hydrogeochemical quality of earthly bore potable water in Haridwar, Uttarakhand, India. Radon activity concentrations in water samples ranged from 0.59 ± 0.04 to 57.32 ± 4.39 Bq/L. The average activity concentration of radon is estimated as 10.46 ± 1.05 Bq/L. Annual Effective Inhalation dose to humans ranged from 1.48 μSv/Y to 144.45 μSv/Y with an average value of 26.36 μSv/Y. Ca2+ > Na+ > Mg2+ > K+ and HCO3− > CaCO3− > SO42− > Cl− > NO3− > F− were the concentration orders of the primary cations and anions. The majority of tests contained acceptable levels of ions and TDS, indicating that the region's groundwater is safe for consumption. For irrigation purposes, the sodium absorption rate, sodium percentage, and magnesium risks were examined. The weathering of rocks was discovered to be the key factor influencing the chemistry of the groundwater in the region. The spatial patterns of observed fluctuations were investigated using the collected data set. [ABSTRACT FROM AUTHOR]

A total of 205 tardigrades representing two orders, five families, nine genera and ten species were extracted from a moss sample (104 tardigrades) and a lichen sample (101 tardigrades) collected near Missoula, Montana, in 2016. Three of the species are new to Montana and one is new to science, Platicrista loloensis nov. sp., which is distinguished by its smooth cuticle, the presence of internal cuticular bars at the base of the claws of legs II and III and a median cuticular bar between the claws of leg IV. [ABSTRACT FROM AUTHOR]

Tardigrades withstand ionizing irradiation levels ∼500 times higher than humans can tolerate. Two recent papers shed light on how this might be achieved — via the transcriptional induction of DNA repair genes, the induction of a radioprotective DNA-binding protein, and possibly also the heightened capacity of repair proteins. [ABSTRACT FROM AUTHOR]

In recent decades, there has been notable variability in the occurrence, frequency, and intensification of cyclones worldwide, and a significant trend has emerged in the northern Indian Ocean, notably the Arabian Sea. The recent cyclone, Biparjoy, occurred in June 2023 and stands out as a significant event among these occurrences. Through an extensive analysis utilizing available datasets (both in-situ and model-based) along the vertical trajectory of cyclone paths, it has been ascertained that the intensity of cyclones is influenced by the advection of warm saline (referred to as "Spicy") water originating north of the cyclone's track. This influx of high-saline waters occurs at various depths, inducing alterations in the vertical water column configuration. Notably, the diffusion of heat overtakes that of salt, resulting in the gradual dispersion of the saline water. These high salinity levels are prevalent at depths ranging from 0 to 300 m, with a pronounced concentration up to 100 m below the surface. The presence of these warm saline waters overlying the colder, fresher waters gives rise to a phenomenon known as "salt fingering" (45o < Tu < 90o), which establishes a stable surface layer predominantly controlled by temperature gradients. This stable surface layer, extending up to approximately 50 m in depth holding a substantial heat, fostering a positive feedback loop that amplifies cyclone intensity. As the spiciness of the Arabian Sea experiences an ascending trend in recent years, the continued extension of saline water advection bears intense implications for upper ocean heat content. This, in turn, creates a favorable environment for the formation and rapid intensification of cyclones. [ABSTRACT FROM AUTHOR]

Tardigrades, commonly known as water bears, are enigmatic organisms characterized by their remarkable resilience to extreme environments despite their simple and compact body structure. To date, there is still much to understand about their evolutionary and developmental features contributing to their special body plan and abilities. This research provides preliminary insights on the conserved and specific gene expression patterns during embryonic development of water bears, focusing on the species Hypsibius exemplaris. The developmental dynamic expression analysis of the genes with various evolutionary age grades indicated that the mid‐conserved stage of H. exemplaris corresponds to the period of ganglia and midgut development, with the late embryonic stage showing a transition from non‐conserved to conserved state. Additionally, a comparison with Drosophila melanogaster highlighted the absence of certain pathway nodes in development‐related pathways, such as Maml and Hairless, which are respectively the transcriptional co‐activator and co‐repressor of NOTCH regulated genes. We also employed Weighted Gene Co‐expression Network Analysis (WGCNA) to investigate the expression patterns of tardigrade‐specific genes during embryo development. Our findings indicated that the module containing the highest proportion of tardigrade‐specific genes (TSGs) exhibits high expression levels before the mid‐conserved stage, potentially playing a role in glutathione and lipid metabolism. These functions may be associated to the ecdysone synthesis and storage cell formation, which is unique to tardigrades. [ABSTRACT FROM AUTHOR]