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Studies of tardigrade biology have been severely limited by the sparsity of appropriate quantitative techniques, informative on a single-organism level. Therefore, many studies rely on motility-based survival scoring and quantifying reproductive success. Measurements of O2 respiration rates, as an integrating expression of the metabolic activity of single tardigrades, would provide a more comprehensive insight into how an individual tardigrade is responding to specific environmental factors or changes in life stages. Here we present and validate a new method for determining the O2 respiration rate (nmol O2 mg−1 hour−1) of single tardigrades under steady state, using O2-microsensors. As an example, we show that the O2 respiration rate determined in MilliQ water for individuals of Richtersius coronifer and of Macrobiotus macrocalix at 22 °C was 10.8±1.8 nmol O2 mg−1 hour−1 and 13.1±2.3 nmol O2 mg−1 hour−1, respectively.

STORAGE CELLS AND THEIR ROLE IN TARDIGRADE PHYSIOLOGY Abstract Tardigrades possess remarkable tolerance to numerous stress conditions (e.g. almost complete desiccation, exposure to very low sub-zero temperature, heat stress and even exposure to space in low Earth orbit). Indeed, they are among the most radiation-resistant multi-cellular organisms. The body cavity of tardigrades is filled with the storage cells (SC). Their role in anhydrobiosis has been discussed. The main objectives of this work were to analyse (i) the occurrence of mitosis in SC, (ii) the factors constraining anhydrobiotic survival, and (iii) the general ultrastructure of SC and their ultrastructure concerning the stress conditions. Our model species, R. cf. coronifer is one of the most extensively studied tardigrades concerning anhydrobiosis. Comprehensive histochemical techniques were used in combination with SEM, TEM, and confocal microscopy. First, mitotic divisions of tardigrade SC occur with a higher frequency in juveniles than in adults and correlate with animal growth. Mitosis is more frequent in moulting tardigrades, but the overall mitotic index is low. Furthermore, tardigrades of R. cf. coronifer can survive the maximum of 6 repeated desiccation cycles with significantly declining survival rate with repeated desiccations and...

The designation of a neotype for Macrobiotus coronifer Richters, 1903 (now the type species of the genus Richtersius Pilato & Binda, 1989) by Maucci & Ramazzotti (1981) with type locality Bodø in Norway is shown to be invalid as it does not comply with the International Code of Zoological Nomenclature (Article 75.3.4). Furthermore, the specimen selected by Maucci & Ramazzotti (1981) is not from the original type locality, and the superficial and outdated documentation prevent a reliable identification of the species. A Code-compliant neotype is therefore designated. The new neotype was collected from the original locus typicus in Svalbard and described with standard light microscopy, detailed scanning electron microscopy imaging, DNA barcodes and a transcriptome, which makes it ideally suited for stabilising the taxonomy and nomenclature of Richtersius coronifer (Richters, 1903).

The aim of this study was to analyze tolerance to heavy ions in desiccated animals of the eutardigrade Richtersius coronifer and the bdelloid rotifer Mniobia russeola within the STARLIFE project. Both species were exposed to iron (Fe) and helium (He) ions at the Heavy Ion Medical Accelerator in Chiba (HIMAC) in Chiba, Japan, and to X-rays at the German Aerospace Center (DLR) in Cologne, Germany. Results show no effect of Fe and He on viability up to 7 days post-rehydration in both R. coronifer and M. russeola, while X-rays tended to reduce viability in R. coronifer at the highest doses. Mean egg production rate tended to decline with higher doses in R. coronifer for all radiation types, but the pattern was not statistically confirmed. In M. russeola, there was no such tendency for a dose response in egg production rate. These results confirm the previously reported high tolerance to high linear energy transfer (LET) radiation in tardigrades and show for the first time that bdelloid rotifers are also very tolerant to high-LET radiation. These animal phyla represent the most desiccation- and radiation-tolerant animals on Earth and provide excellent eukaryotic models for astrobiological research. Key Words: Tardigrada-Rotifera-Radiation tolerance-Heavy ions-X-rays. Astrobiology 17, 163-167.

Although tardigrades are sometimes reported as eutelic animals, mitosis has been reported in several somatic tissues of adult eutardigrades. The occurrence of cell division in storage cells is part ...

Important contributions have been made to the systematics of Eutardigrada in recent years, but these have also revealed that several taxa are polyphyletic and that cryptic species are present. To shed light on the taxonomy and systematic position of the genus Richtersius (Eutardigrada, Macrobiotoidea), six populations attributed to Richtersius coronifer were collected and analysed from morphological (light and scanning electron microscopy) and molecular (mitochondrial cytochrome oxidase subunit 1, 18S, 28S) points of view. In particular, a new morphometric index (claw common tract: length of the common tract of the claw/total claw length × 100) and a new morphological character (stalk system) were introduced. Our integrative study was able to unveil the ‘cryptic’ species diversity within Richtersius, showing that the genus contains more than one evolutionary lineage. A morphological peculiarity in the animals of all lineages is the dimorphism in the morphology of the cuticle. Cuticular pores are present in the newborns and are lost with the first moult; this morphological change represents a novelty in the life cycle of eutardigrades. The phylogenetic analyses carried out on Richtersius populations and other Macrobiotoidea show that Richtersius is closely related to Macrobiotus islandicus, whereas Adorybiotus granulatus is more related to Richtersius and M. islandicus than to other members of the genus Macrobiotus (type genus of Macrobiotidae); therefore, the genus Macrobiotus and the family Macrobiotidae are not monophyletic. Based on these results, the new genus Diaforobiotus (for M. islandicus) and the new family Richtersiidae (composed of Richtersius, Diaforobiotus gen. nov., and Adorybiotus) are established.

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

Pollen- and non-pollen-palynomorphs (NPP) analytical studies of the northwestern part of Spitsbergen were conducted between 1988 and 1991. As well as pollen from local native flora and more dispersed species, some well preserved remains of tardigrada exuvia, buccal tubes and eggs were found. This study reviewed the remains of at least six tardigrade taxa reported:Dactylobiotus ambiguous, Paramacrobiotus richtersigroup,Richtersius coronifer, Macrobiotus hufelandigroup,Macrobiotus peterseniandMinibiotuscf.intermedius, which are reassessed and determined more accurately. These findings provide some new insights into the past environmental conditions and changes for Spitsbergen. Based on the present research it can be concluded that tardigrade remains are frequent NPP elements of pollen analyses from lake, peat bogs and detritus sub-fossil sediment cores, at least in polar regions. It can also be stated that tardigrades can be considered indicators in further palaeontological studies helping to reconstruct past environmental conditions (for example humidity) for some regions. However, the knowledge of tardigrades in these types of analyses is still rather poor.

Global knowledge of tardigrade diversity is limited, and there still are regions with poorly studied fauna, such as Nepal. We applied an integrative taxonomy approach to describe a new tardigrade species from this area. The presented analysis was based on morphological and morphometrical data (using both light and scanning electron microscopy) and combined with multilocus molecular data (nuclear barcode sequences, i.e. 18S rRNA, 28S rRNA and ITS-2, and one mitochondrial COI sequences). The p-distances enabled an independent verification of Macrobiotus wandaesp. nov. as a species new to science. Molecular data allowed us to determine the phylogenetic position of Mac. wandaesp. nov. within the hufelandi group. Based on egg morphology, i.e. porous egg chorion and processes in shape of cones with terminal discs, new species is most similar to Mac. biserovi, Mac. denticulus, Mac. diversus, Mac. glebkai, Mac. macrocalix, Mac. maculatus and Mac. ramoli. But it differs from them mainly by some morphological and morphometrical characters of eggs (number of egg processes on circumference, details of egg shell sculpture, and morphology of terminal discs of eggs) and adults (oral cavity armature type, morphology of lunule and presence or absence of leg granulation). Moreover, we report from Nepal six other tardigrade taxa: Calohypsibius cf. maliki, Echiniscus blumi, Echiniscus nepalensis, Mesobiotus cf. furciger, Richtersius coronifer and Stellariscus cf. latifasciatus.

Tardigrades represent an invertebrate phylum with no circulatory or respiratory system. Their body cavity is filled with free storage cells of the coelomocyte-type, which are responsible for important physiological functions. We report a study comparing the ultrastructure of storage cells in anhydrobiotic and hydrated specimens of the eutardigrade Richtersius coronifer. We also analysed the effect of temperature stress on storage cell structure. Firstly, we verified two types of ultrastructurally different storage cells, which differ in cellular organelle complexity, amount and content of reserve material and connection to oogenetic stage. Type I cells were found to differ ultrastructurally depending on the oogenetic stage of the animal. The main function of these cells is energy storage. Storage cells of Type I were also observed in the single male that was found among the analysed specimens. The second cell type, Type II, found only in females, represents young undifferentiated cells, possibly stem cells. The two types of cells also differ with respect to the presence of nucleolar vacuoles, which are related to oogenetic stages and to changes in nucleolic activity during oogenesis. Secondly, this study revealed that storage cells are not ultrastructurally affected by six months of desiccation or by heating following this desiccation period. However, heating of the desiccated animals (tuns) tended to reduce animal survival, indicating that long-term desiccation makes these animals more vulnerable to heat stress. We confirmed the degradative pathways during the rehydration process after desiccation and heat stress. Our study is the first to document two ultrastructurally different types of storage cells in tardigrades and reveals new perspectives for further studies of tardigrade storage cells.

162. Richtersius coronifer (Richters, 1903) sensu lato [T] MacRobiotus coRonifeR F. Richters, 1903 (Teunissen 1938) MacRobiotus coRonifeR Richt. (Iharos 1978) RichteRsia coRonifeR (Richters, 1903) (Binda & Pilato 1987) Terra typica: Svalbard (Spitsbergen) (Norway, Arctic Ocean) Algeria: • 36°40′N, 04°36′E; 1,400 m asl: Tizi Ouzou Province, Akfadou Forest. Binda & Pilato (1987) • 36°38′N, 05°45′E; 1,200 m asl: Jijel Province, M’Sid-Ech-Cheta (Texenna Pass). Binda & Pilato (1987) • 36°28′N, 04°14′E; 1,700 m asl: Tizi Ouzou Province, Massif of Djurdjura (Assouille depression). Binda & Pilato (1987) Democratic Republic of Congo: • 01°24′S, 29°15′E; 2,100 m asl: North Kivu Province, Albert National Park [Virunga National Park], “ Mayumba ” - mountain primary forest island in the plain of lava on the volcano Nyamuragira, soil. Teunissen (1938) Tunisia: • 36°46'36''N, 08°42'45''E; 784 m asl: Jendouba Governorate, Beni M'tir, urban, moss on soil. Gąsiorek et al. (2017) • 36°46′N, 08°41′E; 700 m asl: Jendouba Governorate, surroundings of Ain Draham, moss and lichen on tree (QueRcus saubeR). Iharos (1978) • 36°44'21''N, 08°43'47''E; 516 m asl: Jendouba Governorate, Beni M'tir, forest, moss on soil. Gąsiorek et al. (2017) Record numbers. Algeria: 3, Democratic Republic of Congo: 1, Tunisia: 3; total: 7. Remarks. This largely Holarctic distribution, appears focused in the Arctic, sub-Arctic and montane regions (McInnes 1994). African records appear restricted to northern and montane localities.

162. Richtersius coronifer (Richters, 1903) sensu lato [T] MacRobiotus coRonifeR F. Richters, 1903 (Teunissen 1938) MacRobiotus coRonifeR Richt. (Iharos 1978) RichteRsia coRonifeR (Richters, 1903) (Binda & Pilato 1987) Terra typica: Svalbard (Spitsbergen) (Norway, Arctic Ocean) Algeria: ��� 36��40���N, 04��36���E; 1,400 m asl: Tizi Ouzou Province, Akfadou Forest. Binda & Pilato (1987) ��� 36��38���N, 05��45���E; 1,200 m asl: Jijel Province, M���Sid-Ech-Cheta (Texenna Pass). Binda & Pilato (1987) ��� 36��28���N, 04��14���E; 1,700 m asl: Tizi Ouzou Province, Massif of Djurdjura (Assouille depression). Binda & Pilato (1987) Democratic Republic of Congo: ��� 01��24���S, 29��15���E; 2,100 m asl: North Kivu Province, Albert National Park [Virunga National Park], ��� Mayumba ��� - mountain primary forest island in the plain of lava on the volcano Nyamuragira, soil. Teunissen (1938) Tunisia: ��� 36��46'36''N, 08��42'45''E; 784 m asl: Jendouba Governorate, Beni M'tir, urban, moss on soil. Gąsiorek et al. (2017) ��� 36��46���N, 08��41���E; 700 m asl: Jendouba Governorate, surroundings of Ain Draham, moss and lichen on tree (QueRcus saubeR). Iharos (1978) ��� 36��44'21''N, 08��43'47''E; 516 m asl: Jendouba Governorate, Beni M'tir, forest, moss on soil. Gąsiorek et al. (2017) Record numbers. Algeria: 3, Democratic Republic of Congo: 1, Tunisia: 3; total: 7. Remarks. This largely Holarctic distribution, appears focused in the Arctic, sub-Arctic and montane regions (McInnes 1994). African records appear restricted to northern and montane localities., Published as part of Kaczmarek, ��ukasz, 2017, Annotated zoogeography of non-marine Tardigrada. Part IV: Africa, pp. 1-74 in Zootaxa 4284 (1) on page 58, DOI: 10.11646/zootaxa.4284.1.1, http://zenodo.org/record/1010400, {"references":["Teunissen, R. J. H. (1938) Tardigraden. ExploRation du PaRc National AlbeRt, Mission de Witte, 16, 1 - 21.","Iharos, G. (1978) Data to the knowledge of the Tardigrada fauna of Tunisia. Folia Entomologica HungaRica, 21, 175 - 177.","Gasiorek, P., Morek, W., Stec, D., Marnissi, J. & Michalczyk, L. (2017) The tardigrade fauna of Tunisia, with an integrative description of BRyodelphax maculatus sp. nov. (Tardigrada: Heterotardigrada: Echiniscoidea). African Zoology. http: // dx. doi. org / 10.1080 / 15627020.2017.1297688","McInnes, S. J. (1994) Zoogeographic distribution of terrestrial / freshwater tardigrades from current literature. JouRnal of NatuRal HistoRy, 28, 257 - 352. https: // doi. org / 10.1080 / 00222939400770131"]}

Tardigrades represent one of the main animal groups with anhydrobiotic capacity at any stage of their life cycle. The ability of tardigrades to survive repeated cycles of anhydrobiosis has rarely been studied but is of interest to understand the factors constraining anhydrobiotic survival. The main objective of this study was to investigate the patterns of survival of the eutardigrade Richtersius coronifer under repeated cycles of desiccation, and the potential effect of repeated desiccation on size, shape and number of storage cells. We also analyzed potential change in body size, gut content and frequency of mitotic storage cells. Specimens were kept under non-cultured conditions and desiccated under controlled relative humidity. After each desiccation cycle 10 specimens were selected for analysis of morphometric characteristics and mitosis. The study demonstrates that tardigrades may survive up to 6 repeated desiccations, with declining survival rates with increased number of desiccations. We found a significantly higher proportion of animals that were unable to contract properly into a tun stage during the desiccation process at the 5th and 6th desiccations. Also total number of storage cells declined at the 5th and 6th desiccations, while no effect on storage cell size was observed. The frequency of mitotic storage cells tended to decline with higher number of desiccation cycles. Our study shows that the number of consecutive cycles of anhydrobiosis that R. coronifer may undergo is limited, with increased inability for tun formation and energetic constraints as possible causal factors.

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

212. Richtersius coronifer (Richters, 1903) sensu lato [T] Macrobiotus coronifer Richters (Heinis 1914) Terra typica: Svalbard (Spitsbergen) (Norway, Arctic Ocean) Colombia: • 02° 44 ′N, 76 ° 50 ′W; 2,000 m asl: Cauca Department, above Tambo, moss (Thuidium sp.) and hepatic (Frullania coalita Steph.). Heinis (1914) Record numbers: Colombia: 1; total: 1. Remarks: With a largely Holarctic distribution (McInnes 1994 a), this Colombian record appears anomalous and requires confirmation.

212. Richtersius coronifer (Richters, 1903) sensu lato [T] Macrobiotus coronifer Richters (Heinis 1914) Terra typica: Svalbard (Spitsbergen) (Norway, Arctic Ocean) Colombia: ��� 02�� 44 ���N, 76 �� 50 ���W; 2,000 m asl: Cauca Department, above Tambo, moss (Thuidium sp.) and hepatic (Frullania coalita Steph.). Heinis (1914) Record numbers: Colombia: 1; total: 1. Remarks: With a largely Holarctic distribution (McInnes 1994 a), this Colombian record appears anomalous and requires confirmation., Published as part of Kaczmarek, ��ukasz, Michalczyk, ��ukasz & Mcinnes, Sandra J., 2015, Annotated zoogeography of non-marine Tardigrada. Part II: South America, pp. 1-107 in Zootaxa 3923 (1) on page 88, DOI: 10.11646/zootaxa.3923.1.1, http://zenodo.org/record/241936, {"references":["Richters, F. (1903) Nordische Tardigraden. Zoologisher Anzeiger, 27, 168 - 172.","Heinis, F. (1914) Die Moosfauna Columbiens. Memoires de la Societe des Sciences Naturelles de Neuchatel, 5, 713 - 724.","McInnes, S. J. (1994 a) Zoogeographic distribution of terrestrial / freshwater tardigrades from current literature. Journal of Natural History, 28, 257 - 352. http: // dx. doi. org / 10.1080 / 00222939400770131"]}

The ability of some animal taxa (e.g., nematodes, rotifers, and tardigrades) to enter an ametabolic (cryptobiotic) state is well known. Nevertheless, the phenotypic factors affecting successful anhydrobiosis have rarely been investigated. We report a laboratory study on the effects of body size, reproductive condition, and energetic condition on anhydrobiotic survival in a population of the eutardigrade Richtersius coronifer. Body size and energetic condition interacted in affecting the probability of survival, while reproductive condition had no effect. Large tardigrades had a lower probability of survival than medium-sized tardigrades and showed a positive response in survival to energetic condition. This suggests that energy constrained the possibility for large tardigrades to enter and to leave anhydrobiosis. As a possible alternative explanation for low survival in the largest specimens we discuss the expression of senescence. In line with the view that processes related to ahhydrobiosis are connected with energetic costs we documented a decrease in the size of storage cells over a period of anhydrobiosis, showing for the first time that energy is consumed in the process of anhydrobiosis in tardigrades. (C) 2002 Wiley-Liss, Inc. (Less)

We report a study on anhydrobiotic survival in the eutardigrades Richtersius coronifer and Ramazzottius oberhaeuseri. In each of these species, we investigated the anhydrobiotic survival of two populations, one from Sweden and one from Italy. We found that anhydrobiotic survival was similar in the Swedish and the Italian populations in both species, indicating no divergence with respect to anhydrobiotic capacity. Body size had a strong effect on the probability to recover from anhydrobiosis, but the effect was in opposite direction in the two tardigrade species. Ramazzottius oberhaeuseri had a considerable higher overall survival (66%) than R. coronifer (40%). This result is in line with earlier studies that found R. oberhaeuseri to have a very high water-retentive capacity.

Life unfolds within a framework of constraining abiotic factors, yet some organisms are adapted to handle large fluctuations in physical and chemical parameters. Tardigrades are microscopic ecdysozoans well known for their ability to endure hostile conditions, such as complete desiccation – a phenomenon called anhydrobiosis. During dehydration, anhydrobiotic animals undergo a series of anatomical changes. Whether this reorganization is an essential regulated event mediated by active controlled processes, or merely a passive result of the dehydration process, has not been clearly determined. Here, we investigate parameters pivotal to the formation of the so-called "tun", a state that in tardigrades and rotifers marks the entrance into anhydrobiosis. Estimation of body volume in the eutardigrade Richtersius coronifer reveals an 87 % reduction in volume from the hydrated active state to the dehydrated tun state, underlining the structural stress associated with entering anhydrobiosis. Survival experiments with pharmacological inhibitors of mitochondrial energy production and muscle contractions show that i) mitochondrial energy production is a prerequisite for surviving desiccation, ii) uncoupling the mitochondria abolishes tun formation, and iii) inhibiting the musculature impairs the ability to form viable tuns. We moreover provide a comparative analysis of the structural changes involved in tun formation, using a combination of cytochemistry, confocal laser scanning microscopy and 3D reconstructions as well as scanning electron microscopy. Our data reveal that the musculature mediates a structural reorganization vital for anhydrobiotic survival, and furthermore that maintaining structural integrity is essential for resumption of life following rehydration.

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.

Anhydrobiotic organisms are well known for their resistance to extreme environmental conditions while in the inactive, ametabolic, state. This study confirms that this resistance also transfers to treatments with the fumigant methyl bromide. Live specimens of nematodes, rotifers, and tardigrades were found after 70 h of treatment with methyl bromide. Quantitative estimates of survival in the eutardigrade Richtersius coronifer revealed no difference between treated and untreated samples which had been kept dry for a short time. However, R. coronifer from samples collected 11 months before treatment had lower survival compared to samples collected shortly before the treatment. The fact that anhydrobiotic organisms escape treatments with biocides should be considered a serious problem, both for the food industry and from the perspective of human-mediated spread of organisms.