Echiniscus Testudo Research Articles

The Evolution of Temperature and Desiccation-Related Protein Families in Tardigrada Reveals a Complex Acquisition of Extremotolerance.

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.

Developmental and genomic insight into the origin of the tardigrade body plan.

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.

Multiomics study of a heterotardigrade, Echinisicus testudo, suggests the possibility of convergent evolution of abundant heat-soluble proteins in Tardigrada

BackgroundMany limno-terrestrial tardigrades can enter an ametabolic state, known as anhydrobiosis, upon desiccation, in which the animals can withstand extreme environments. Through genomics studies, molecular components of anhydrobiosis are beginning to be elucidated, such as the expansion of oxidative stress response genes, loss of stress signaling pathways, and gain of tardigrade-specific heat-soluble protein families designated CAHS and SAHS. However, to date, studies have predominantly investigated the class Eutardigrada, and molecular mechanisms in the remaining class, Heterotardigrada, still remains elusive. To address this gap in the research, we report a multiomics study of the heterotardigrade Echiniscus testudo, one of the most desiccation-tolerant species which is not yet culturable in laboratory conditions.ResultsIn order to elucidate the molecular basis of anhydrobiosis in E. testudo, we employed a multi-omics strategy encompassing genome sequencing, differential transcriptomics, and proteomics. Using ultra-low input library sequencing protocol from a single specimen, we sequenced and assembled the 153.7 Mbp genome annotated using RNA-Seq data. None of the previously identified tardigrade-specific abundant heat-soluble genes was conserved, while the loss and expansion of existing pathways were partly shared. Furthermore, we identified two families novel abundant heat-soluble proteins, which we named E. testudo Abundant Heat Soluble (EtAHS), that are predicted to contain large stretches of disordered regions. Likewise the AHS families in eutardigrada, EtAHS shows structural changes from random coil to alphahelix as the water content was decreased in vitro. These characteristics of EtAHS proteins are analogous to those of CAHS in eutardigrades, while there is no conservation at the sequence level.ConclusionsOur results suggest that Heterotardigrada have partly shared but distinct anhydrobiosis machinery compared with Eutardigrada, possibly due to convergent evolution within Tardigrada. (276/350).

Cover Image

The tardigrade brain is key to understanding the evolution of the central nervous systems in Panarthropoda. In this issue of the Journal of Morphology, Gross and coauthors (pp. 1298–1312) reinvestigated the central nervous system of the heterotardigrade Echiniscus testudo using immunohistochemistry to visualize the number and position of tracts, commissures, and neuropils. They document five major synapsinimmunoreactive domains along the body: a large unitary, horseshoe‐shaped neuropil in the head and four neuropils in the trunk ganglia, supporting the hypothesis that the dorsal brain is serially homologous with the ventral trunk ganglia. The cover image shows the dorsal part of the saddle shaped brain [anti‐synapsin immunolabeling (red) and nuclear counterstain (cyan)]. The centrally located synapsin‐rich region, corresponding to the central brain neuropil.

Organization of the central nervous system and innervation of cephalic sensory structures in the water bear Echiniscus testudo (Tardigrada: Heterotardigrada) revisited.

The tardigrade brain has been the topic of several neuroanatomical studies, as it is key to understanding the evolution of the central nervous systems in Panarthropoda (Tardigrada + Onychophora + Arthropoda). The gross morphology of the brain seems to be well conserved across tardigrades despite often disparate morphologies of their heads and cephalic sensory structures. As such, the general shape of the brain and its major connections to the rest of the central nervous system have been mapped out already by early tardigradologists. Despite subsequent investigations primarily based on transmission electron microscopy or immunohistochemistry, characterization of the different regions of the tardigrade brain has progressed relatively slowly and open questions remain. In an attempt to improve our understanding of different brain regions, we reinvestigated the central nervous system of the heterotardigrade Echiniscus testudo using anti-synapsin and anti-acetylated α-tubulin immunohistochemistry in order to visualize the number and position of tracts, commissures, and neuropils. Our data revealed five major synapsin-immunoreactive domains along the body: a large unitary, horseshoe-shaped neuropil in the head and four neuropils in the trunk ganglia, supporting the hypothesis that the dorsal brain is serially homologous with the ventral trunk ganglia. At the same time, the pattern of anti-synapsin and anti-tubulin immunoreactivity differs between the ganglia, adding to the existing evidence that each of the four trunk ganglia is unique in its morphology. Anti-tubulin labeling further revealed two commissures within the central brain neuropil, one of which is forked, and additional sets of extracerebral cephalic commissures associated with the stomodeal nervous system and the ventral cell cluster. Furthermore, our results showing the innervation of each of the cephalic sensilla in E. testudo support the homology of subsets of these structures with the sensory fields of eutardigrades.

The Unique Antimicrobial Recognition and Signaling Pathways in Tardigrades with a Comparison Across Ecdysozoa

Tardigrades are microscopic animals known to withstand unfavorable abiotic conditions. These animals are also constantly exposed to biotic stresses, including parasites and internal microbiomes. However, the tardigrade immune mechanisms against these biotic stresses are largely uncharacterized. Due to the contentious phylogenetic position of tardigrades, it is not intuitive whether they possess an immune system more similar to that of arthropods (e.g., Toll, Imd, and JNK pathways of the Drosophila melanogaster antimicrobial response) or to that of nematodes (e.g., the Tir-1/Nsy-1/Sek-1/Pmk-1/Atf-7 signaling cassette [called Tir-1 pathway here]) in Caenorhabditis elegans). In this study, comparative genomic analyses were conducted to mine homologs of canonical D. melanogaster and C. elegans immune pathway genes from eight tardigrades (Echiniscoides cf. sigismundi, Echiniscus testudo, Hypsibius exemplaris, Mesobiotus philippinicus, Milnesium tardigradum, Paramacrobiotus richtersi, Richtersius cf. coronifer, and Ramazzottius varieornatus) and four non-arthropod ecdysozoans (two onychophorans: Epiperipatus sp. and Opisthopatus kwazululandi; one nematomorph: Paragordius varius; and one priapulan: Priapulus caudatus) in order to provide insights into the tardigrade antimicrobial system. No homologs of the intracellular components of the Toll pathway were detected in any of the tardigrades examined. Likewise, no homologs of most of the Imd pathway genes were detected in any of the tardigrades or any of the other non-arthropod ecdysozoans. Both the JNK and Tir-1 pathways, on the other hand, were found to be conserved across ecdysozoans. Interestingly, tardigrades had no detectable homologs of NF-κB, the major activator of antimicrobial response gene expression. Instead, tardigrades appear to possess NF-κB distantly related NFAT homologs. Overall, our results show that tardigrades have a unique gene pathway repertoire that differs from that of other ecdysozoans. Our study also provides a framework for future studies on tardigrade immune responses.

Echiniscus testudo (Doyère, 1840) in New Zealand: anthropogenic dispersal or evidence for the ‘Everything is Everywhere’ hypothesis?

ABSTRACTMany species of microscopic invertebrates, such as tardigrades or rotifers, have been traditionally regarded as cosmopolitan. This conviction was based on classical taxonomic observations of very similar phenotypes across the globe and hypothetical abilities of micrometazoans for large-scale dispersal with air and water currents. However, several recent studies showed that micrometazoan species may have restricted geographic ranges, suggesting that microscopic size is not the only determinant of dispersal. Here, we describe the first Australasian record of Echiniscus testudo, a heterotardigrade originally described from the Holarctic. Morphological and genetic analyses gave congruent conclusions and confirmed that European and New Zealand populations represent a single species. Importantly, however, without broader sampling in primeval localities, it is not possible to test whether the New Zealand record of E. testudo is a result of natural dispersal or whether the species was brought to Australasia by humans.

The complete mitochondrial genome of Echiniscus testudo (Heterotardigrada: Echiniscidae)

The complete mitchondrial genome of Echiniscus testudo, a cosmopolitan heterotardigrade collected in Japan, has been sequenced using a single molecule real-time (SMRT) sequencing long read after whole genome amplification from a single individual. The genome has a total length of 15,817 bp, consisting of 13 protein-coding genes, 20 tRNA, 2 rRNA genes, and an AT-rich control region. The nucleotide composition was extremely AT-rich, with 78.41% AT. Being in a different class of the phylum Tardigrada, there is a large sequence divergence from the previously reported mitochondrial genome of the eutardigrade Ramazzottius varieornatus, but the gene order of protein-coding genes are mostly conserved. This is the first report of a complete mitochondrial genome of a heterotardigrade.

Three Echiniscidae species (Tardigrada: Heterotardigrada) new to the Polish fauna, with the description of a new gonochoristic Bryodelphax Thulin, 1928.

During a faunistic survey in the Pieniny and Tatra Mountains three species of Echiniscidae new to Poland, including one new to science, were found. Bryodelphax instabilis sp. nov. is characterised by an instable number of ventral plates, deep faceting of the scapular plate, having dorsal plates covered either with pseudopores or pores, and striking sexual dimorphism. Two first records, namely Echiniscus militaris and E. spiniger, are rare taxa of upland-mountain character, which have already been reported from a few European countries since the original description at the beginning of the XXth century. The interspecific appendage length variability and development of pedal plates in the spinulosus group, to which E. spiniger belongs, and their taxonomic importance is discussed. Notes relating to sexual dimorphism within the newly recorded Pseudechiniscus facettalis, are also presented. Echiniscus testudo is reported from the Polish part of the Tatra Mountains for the first time. Succeeding findings confirm the high tardigrade α-diversity in the Polish mountain ranges. An amended key for Polish Heterotardigrada is provided.

First record of the tardigrade Echiniscus testudo (Doyère, 1840) from northeast of Iran (Heterotardigrada: Echiniscidae)

Tardigrada is a phylum closely allied with the arthropods. They are small (0.05-1.20 mm), hygrophilous micrometazoans, have four pairs of lobe-like legs and are either carnivorous or feed on plant material. Most of the tardigrade species are limno-terrestrial. In two moss and lichen samples collected in Mashhad, one heterotardigrade species was found. Echiniscus testudo (Doyere, 1840) belongs to the Echiniscidae group and differs from most of other species in this group mainly by having a different claw configuration and by some morphometric characters. This study is the first report of tardigrades from Iran.

An integrative redescription of Echiniscus testudo (Doyère, 1840), the nominal taxon for the class Heterotardigrada (Ecdysozoa: Panarthropoda: Tardigrada)

The phylum Tardigrada is divided into three classes: Eutardigrada, Mesotardigrada, and Heterotardigrada. Armoured limno-terrestrial taxa within the family Echiniscidae represent over half of the described species in the last class, and exhibit more consistent morphology in comparison with their closest marine relatives. The main aim of this study was to redescribe comprehensively the nominal species for Heterotardigrada, Echiniscus testudo, applying an integrative approach. Our integrative study confirmed that both forms E. testudo trifilis and E. t. quadrifilis (with three and four lateral body cirri, respectively), although differing in the COI sequence, indeed represent a single species. Finally, we discuss the taxonomic status of E. glaber, E. filamentosus, and E. filamentosus mongoliensis. As a result, we designate the first two species as junior synonyms of E. testudo but we recognise the validity of the last taxon and we elevate it to the species level as Echiniscus mongoliensiscomb. nov. This study, by providing a detailed description of the nominal taxon and the diagnosis for the genus Echiniscus, opens the way for confident descriptions of closely related species and for erecting new genera from within the largest polyphyletic tardigrade genus.

Comparative Investigation of Copper Tolerance and Identification of Putative Tolerance Related Genes in Tardigrades.

Tardigrades are microscopic aquatic animals renowned for their tolerance toward extreme environmental conditions. The current study is the first to investigate their tolerance toward heavy metals and we present a novel tardigrade toxicant tolerance assay based on activity assessments as a measure of survival. Specifically, we compare tolerance toward copper in four species representing different evolutionary lineages, habitats and adaptation strategies, i.e., a marine heterotardigrade, Echiniscoides sigismundi, a limno-terrestrial heterotardigrade, Echiniscus testudo, a limno-terrestrial eutardigrade, Ramazzottius oberhaeuseri, and a marine eutardigrade, Halobiotus crispae. The latter was sampled at a time of year, when the population is predominantly represented by aberrant P1 cysts, while the other species were in normal active states prior to exposure. Based on volume measurements and a general relation between body mass and copper tolerance, expected tardigrade EC50 values were estimated at 0.5–2 μg l−1. Following 24 h of exposure, tolerance was high with no apparent link to lineage or habitat. EC50s (95% CI), 24 h after exposure, were estimated at 178 (168–186) and 310 (295–328) μg l−1, respectively, for E. sigismundi and R. oberhaeuseri, whereas E. testudo and H. crispae were less affected. Highest tolerance was observed in H. crispae with a mean ± s.e.m. activity of 77 ± 2% (n = 3) 24 h after removal from ~3 mg l−1 copper, suggesting that tardigrade cysts have increased tolerance toward toxicants. In order to identify putative tolerance related genes, an E. sigismundi transcriptome was searched for key enzymes involved in osmoregulation, antioxidant defense and copper metabolism. We found high expression of Na/K ATPase and carbonic anhydrase, known targets for copper. Our transcriptome, furthermore, revealed high expression of antioxidant enzymes, copper transporters, ATOX1, and a Cu-ATPase. In summary, our results indicate that tardigrades express well-known key osmoregulatory enzymes, supporting the hypothesis that copper inhibits sodium turnover as demonstrated for other aquatic organisms. Tardigrades, nevertheless, have high tolerance toward the toxicant, which is likely linked to high expression of antioxidant enzymes and an ability to enter dormant states. Tardigrades, furthermore, seem to have a well-developed battery of cuproproteins involved in copper homeostasis, providing basis for active copper sequestering and excretion.

Osmotic stress tolerance in semi-terrestrial tardigrades

Little is known about ionic and osmotic stress tolerance in tardigrades. Here, we examine salt stress tolerance in Ramazzottius oberhaeuseri and Echiniscus testudo from Niva (Denmark) and address whether limno-terrestrial tardigrades can enter a state of quiescence (osmobiosis) in the face of high external osmolyte concentrations. Direct transfers into NaCl solutions showed an upper tolerance level of around 600 mOsm kg−1 in R. oberhaeuseri and 200 mOsm kg−1 in E. testudo. During salt exposures, R. oberhaeuseri contracted into a ‘tun’, whereas E. testudo remained active leaving it more susceptible to acute effects of the ions. Further experiments focused on the more resilient R. oberhaeuseri, which entered a tun and readily regained activity when directly exposed to polyethylene glycol and sucrose of up to 872 ± 0 and 813 ± 3 mOsm kg−1, respectively, revealing a higher tolerance towards non-ionic osmolytes as compared to NaCl. Ramazzottius oberhaeuseri furthermore readily regained activity following gradual increases in non-ionic osmolytes and NaCl of up to 2434 ± 28 and 1905 ± 3 mOsm kg−1, respectively, showing that short-term acclimation promoted salt stress tolerance. Our results suggest that the limno-terrestrial R. oberhaeuseri enters a state of quiescence in the face of high external osmotic pressure and that it, in this state, is highly tolerant of ionic and osmotic stress.

Genetic diversity in the parthenogenetic reproducing tardigrade Echiniscus testudo (Heterotardigrada: Echiniscoidea)

Little is known about the genetic structure of microscopic animals from mosses and lichens. A few studies have investigated the geographic variation in tardigrades from mosses, but so far no study has investigated the intra-population or local clonal lineage variation. Echiniscus testudo (Echiniscoidea: Echiniscidae) belongs to a large cosmopolitan genus of terrestrial tardigrades comprising more than 150 species. It is a common tardigrade in mosses in the temperate part of the Northern hemisphere, and is highly tolerant of desiccation and freezing. In a previous study, we reported a maximum of 1.28% sequence variation (uncorrected p-distance) in cytochrome c oxidase subunit I (COI) haplotypes between clonal lineages covering a large geographical area. However, in this previous study we used pooled specimens to constitute a sample, and the genetic diversity from single specimens within a locality therefore remains unknown. Accordingly, the present study investigates the COI sequence variation and haplotype diversity between single specimens of E. testudo collected at three Danish localities, separated by 80 m and 186 km. A total of 10 COI haplotypes were found in the present study (Et2, Et3, Et9, Et12-Et18); only three of these were previously reported (Et2, Et3 and Et9). The uncorrected COI sequence diversity ranged between 0-2.07%, with haplotype Et18 having the highest genetic difference. The second most variable haplotypes (Et14, Et15, and Et17) all showed a maximum diversity of 1.19% compared to the other haplotypes. No general pattern of haplotype distribution was evident. Our data suggest that E. testudo has dispersed across the Baltic sea as haplotypes Et3, Et13 and Et14 are present at all three localities. The most likely dispersal mode is passive wind dispersal in the cryptobiotic tun stage. The current study emphasises that numerous sequences from single specimens are needed to describe the genetic diversity within single moss cushions.

The architecture of the nervous system of Echiniscus testudo (Echiniscoidea, Heterotardigrada)

Despite the fact that there are several descriptions of the nervous system of Tardigrada there is still dispute about how to interpret the organisation of these structures. Is the structure of the brain homologous to segmental equivalents of the arthropod brain or not? The latest studies concerning these questions concentrate on specimens from the taxon Eutardigrada, but a representative of Heterotardigrada has been missing. Therefore, in this immunohistochemical study the organisation of the nervous system of Echiniscus testudo is investigated and can be described as follows. In the brain of E. testudo several distinct regions can be recognised. These are the anterior, dorsal, dorsoventral, inner and posterior clusters. Furthermore a ventral cluster can be detected that is connected to the dorsoventral clusters. The brain is followed by four ventral ganglia that are positioned slightly anterior to their corresponding pair of legs. The brain and the first ventral ganglion are connected via connectives showing tyrosinated α-tubulin and RFamide immunoreactivity. A connection between the first ventral ganglion and the ventral cluster could not be detected, at least not with our antibody set. In longitudinal direction the ventral ganglia are chained by connectives, and transversal interconnections via commissures are present. In addition to the commissures connecting the hemiganglia, three commissures could be detected lying anterior to the second, the third and the fourth ventral ganglion. In some specimens between the second and the third ganglion, bilaterally arranged neurites could be detected that run in a loop to the dorsal part of the specimens. The hereindescribed organisation is compared with previously published data on the nervous system of Tardigrada, and we conclude that the lobate organisation of the brain of E. testudo comprises an arrangement due to functional needs rather than to reflect an organisation into arthropod-like proto-, deuto- and trito-cerebrum.

Inorganic ion composition in Tardigrada: cryptobionts contain large fraction of unidentified organic solutes

Many species of tardigrades are known to tolerate extreme environmental stress, yet detailed knowledge of the mechanisms underlying the remarkable adaptations of tardigrades is still lacking, as are answers to many questions regarding their basic biology. Here, we present data on the inorganic ion composition and total osmotic concentration of five different species of tardigrades (Echiniscus testudo, Milnesium tardigradum, Richtersius coronifer, Macrobiotus cf. hufelandi and Halobiotus crispae) using high-performance liquid chromatography and nanoliter osmometry. Quantification of the ionic content indicates that Na(+) and Cl(-) are the principal inorganic ions in tardigrade fluids, albeit other ions, i.e. K(+), NH4(+), Ca(2+), Mg(2+), F(-), SO4(2-) and PO4(3-) were also detected. In limno-terrestrial tardigrades, the respective ions are concentrated by a large factor compared with that of the external medium (Na(+), ×70-800; K(+), ×20-90; Ca(2+) and Mg(2+), ×30-200; F(-), ×160-1040, Cl(-), ×20-50; PO4(3-), ×700-2800; SO4(2-), ×30-150). In contrast, in the marine species H. crispae, Na(+), Cl(-) and SO4(2-) are almost in ionic equilibrium with (brackish) salt water, while K(+), Ca(2+), Mg(2+) and F(-) are only slightly concentrated (×2-10). An anion deficit of ~120 mEq l(-1) in M. tardigradum and H. crispae indicates the presence of unidentified ionic components in these species. Body fluid osmolality ranges from 361±49 mOsm kg(-1) in R. coronifer to 961±43 mOsm kg(-1) in H. crispae. Concentrations of most inorganic ions are largely identical between active and dehydrated groups of R. coronifer, suggesting that this tardigrade does not lose large quantities of inorganic ions during dehydration. The large osmotic and ionic gradients maintained by both limno-terrestrial and marine species are indicative of a powerful ion-retentive mechanism in Tardigrada. Moreover, our data indicate that cryptobiotic tardigrades contain a large fraction of unidentified organic osmolytes, the identification of which is expected to provide increased insight into the phenomenon of cryptobiosis.

Extreme stress tolerance in tardigrades: surviving space conditions in low earth orbit

Abstract Most terrestrial tardigrade species possess the ability to enter a reversible ametabolic state termed anhydrobiosis in response to desiccation. In theanhydrobiotic state, tardigrades display an incredible capacity to tolerate extreme environmental stress, not necessarily encountered in theirnatural habitat. In this study, we determine the effect of different extreme stresses on initial survival, long-term survival and fecundity of selectedspecies of limno-terrestrial tardigrades. The primary focus was to assess the effect of cosmic radiation. This was achieved through the RoTaRad(Rotifers, Tardigrades and Radiation) project on the BIOPAN 6 mission, funded by Agenzia Spaziale Italiana under the European Space Agency.To test their tolerance of space environment, tardigrades were sent into low earth orbit, and exposed to cosmic radiation and a microgravityenvironment. Experiments on Whatman-3 filters show an effect of cosmic radiation on the survival of the eutardigrade Richtersius coronifer justafter returning to Earth; however, after 2 years of desiccation on Whatman-3 filters, none of the tardigrades previously exposed to cosmicradiation could be revived. In a microcosmos experiment, the tardigrades R. coronifer, Ramazzottius oberhauseri and Echiniscus testudo weredesiccated on a moss substrate together with rotifers and nematodes. Very low survival rates were observed in this experiment, likely due to theapplied desiccation protocol. Embryos of the tardigrade Milnesium tardigradum were also exposed to cosmic radiation; they all hatched in thelaboratory after the flight. In addition, experiments testing extreme cold and vacuum tolerance in R. coronifer show that tardigrades inanhydrobiosis are unaffected by these conditions.Key words: Tardigrada – anhydrobiosis – cosmic radiation – extreme freezing – vacuum

Tardigrade workbench: comparing stress-related proteins, sequence-similar and functional protein clusters as well as RNA elements in tardigrades

BackgroundTardigrades represent an animal phylum with extraordinary resistance to environmental stress.ResultsTo gain insights into their stress-specific adaptation potential, major clusters of related and similar proteins are identified, as well as specific functional clusters delineated comparing all tardigrades and individual species (Milnesium tardigradum, Hypsibius dujardini, Echiniscus testudo, Tulinus stephaniae, Richtersius coronifer) and functional elements in tardigrade mRNAs are analysed. We find that 39.3% of the total sequences clustered in 58 clusters of more than 20 proteins. Among these are ten tardigrade specific as well as a number of stress-specific protein clusters. Tardigrade-specific functional adaptations include strong protein, DNA- and redox protection, maintenance and protein recycling. Specific regulatory elements regulate tardigrade mRNA stability such as lox P DICE elements whereas 14 other RNA elements of higher eukaryotes are not found. Further features of tardigrade specific adaption are rapidly identified by sequence and/or pattern search on the web-tool tardigrade analyzer http://waterbear.bioapps.biozentrum.uni-wuerzburg.de. The work-bench offers nucleotide pattern analysis for promotor and regulatory element detection (tardigrade specific; nrdb) as well as rapid COG search for function assignments including species-specific repositories of all analysed data.ConclusionDifferent protein clusters and regulatory elements implicated in tardigrade stress adaptations are analysed including unpublished tardigrade sequences.

Tardigrada of Xinjiang Uygur Autonomous Region, China

Relatively little is known of the Tardigrada fauna of China, and there are no previous tardigrade records for Xinjiang Uygur Autonomous Region, China's largest administrative division. Moss specimens of the Missouri Botanical Garden Herbarium (St. Louis, U.S.A.) were used as a source of tardigrades from this region. Of the 270 moss specimens sampled, 78 yielded tardigrades. Species found were Bryodelphax asiaticus, Cornechiniscus holmeni, Echiniscus blumi, Echiniscus canadensis, Echiniscus granulatus, Echiniscus testudo, Echiniscus trisetosus, Macrobiotus alekseevi, Macrobiotus mauccii, Milnesium asiaticum, Milnesium longiungue, and Milnesium tardigradum. Of the species found, the Heterotardigrada are better represented, which is probably a reflection of the higher altitudes at which the samples were taken and the arid environment of the region; the species found are primarily ones considered to be xerophilic or montane. Seven species new to China are reported.

A molecular study of the tardigrade Echiniscus testudo (Echiniscidae) reveals low DNA sequence diversity over a large geographical area

In the present study we investigate the genetic diversity within the asexually reproducing tardigrade Echiniscus testudo. The present study is the first to sample a tardigrade species for comparison of DNA sequence diversity between widely separated samples. Echiniscus testudo was sampled at 13 localities spanning three continents. DNA sequences of the mitochondrial COI gene and the nuclear ITS2 sequence were used to investigate the genetic diversity and phylogeographic structure of the various asexual lineages. Terrestrial tardigrades with the capability of entering a cryptobiotic state are assumed to have a high passive dispersal potential through airborne transport. Our results show moderate (ITS2) to high (COI) haplotype diversity and low sequence diversity that indicate evolution of haplotypes within distinct asexual lineages and a high dispersal potential. No isolation by distance was detected by Mantel tests. Different phylogeny inference methods (neighbor-joining, maximum parsimony, maximum likelihood and Bayesian inference) revealed little topological resolution, but minimum spanning networks showed some phylogeographic patterns. The COI and ITS2 minimum spanning networks show patterns that indicate dispersal of several haplotypes from founding populations. In conclusion our data show a low genetic diversity and a relatively high haplotype diversity indicating that E. testudo is a young species with a high dispersal potential.