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Abstract Background Science curricula and teachers should emphasize evolution in a manner commensurate with its importance as a unifying concept in science. The concept of adaptation represents a first step to understand the results of natural selection. We settled an experimental project of alternative didactic to improve knowledge of organism adaptation. Students were involved and stimulated in learning processes by creative activities. To set adaptation in a historic frame, fossil records as evidence of past life and evolution were considered. Results The experimental project is schematized in nine phases: review of previous knowledge; lesson on fossils; lesson on fantastic animals; planning an imaginary world; creation of an imaginary animal; revision of the imaginary animals; adaptations of real animals; adaptations of fossil animals; and public exposition. A rubric to evaluate the student's performances is reported. The project involved professors and students of the University of Modena and Reggio Emilia and of the "G. Marconi" Secondary School of First Degree (Modena, Italy). Conclusion The educational objectives of the project are in line with the National Indications of the Italian Ministry of Public Instruction: knowledge of the characteristics of living beings, the meanings of the term "adaptation", the meaning of fossils, the definition of ecosystem, and the particularity of the different biomes. At the end of the project, students will be able to grasp particular adaptations of real organisms and to deduce information about the environment in which the organism evolved. This project allows students to review previous knowledge and to form their personalities.

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]

Like meiofauna in general, tardigrades are often neglected in ecological and environmental surveys. Tardigrades occur in all parts of the world, from deep marine sediments to alpine environments, and are present in most ecosystems. They are therefore potentially good candidates for biomonitoring programs. However, sampling of these minute animals is both tedious and time-consuming, impeding their inclusion in large-scale ecological surveys. In this study we argue that using a multi-marker metabarcoding approach on environmental DNA (eDNA) partly can overcome this barrier. Samples of moss, lichens, and leaf litter were investigated both by morphologybased methods and DNA metabarcoding, and the results were compared in terms of tardigrade diversity and community composition of the sampled microhabitats. DNA metabarcoding using three markers detected more species of tardigrades than identification by morphology in most samples. Also, metabarcoding detected the same community differences and microhabitat distribution patterns as morphology-based methods. In general, metabarcoding of litter samples was unreliable, with only one out of three markers consistently amplifying and detecting tardigrades. The low availability of tardigrade reference sequences in public databases restricts the taxonomic resolution in eDNA surveys, but this impediment is partly circumvented by utilizing multiple markers. Key words: Tardigrada, environmental DNA, eDNA, 18S, COI, DNA barcoding. Comme la meiofaune de maniere generale, les tardigrades sont souvent negliges dans les inventaires ecologiques et environnementaux. Les tardigrades sont rencontres dans toutes les parties de monde, des sediments dans les profondeurs marines jusqu'aux environnements alpins, et sont presents dans la plupart des ecosystemes. Ils constituent ainsi de bons candidats potentiels pour des programmes de biosurveillance. Cependant, l'echantillonnage de ces animaux minuscules est a la fois fastidieux et couteux en temps, ce qui represente une entrave a leur inclusion dans des inventaires ecologiques a grande echelle. Dans cette etude, les auteurs avancent que l'utilisation d'une approche de metacodage a barres a l'aide de multiples marqueurs sur des ADN environnementaux (ADNe) pourrait permettre de partiellement surmonter ces entraves. Des echantillons de mousses, de lichens et de litiere de feuilles ont ete analyses a la fois par des methodes fondees sur la morphologie et le metacodage a barres de l'ADN. Les resultats obtenus ont ete compares aux micro-habitats etudies en matiere de diversite des tardigrades et de composition de la communaute. Le metacodage a barres de l'ADN a l'aide de trois marqueurs a permis de detecter plus d'especes de tardigrades que l'identification morphologique chez la plupart des echantillons. De plus, le metacodage a barres a detecte les memes differences en matiere de composition des communautes et de distribution au sein des micro-habitats que les methodes fondees sur la morphologie. En general, le metacodage a barres des echantillons de litiere se sont averes peu fiables, avec un seul des trois marqueurs permettant d'amplifier et de detecter des tardigrades. Le faible nombre de sequences de reference pour les tardigrades au sein des bases de donnees publiques limite la resolution taxonomique dans les analyses d'ADNe, mais cette entrave est partiellement contournee en faisant appel a des marqueurs multiples. Mots-cles: Tardigrada, ADN environnemental, ADNe, 18S, COI, codage a barres de l'ADN., Introduction Tardigrades are hygrophilous, microscopic invertebrates inhabiting nearly all ecosystems on earth. Currently, the phylum holds about 1270 described species (Degma et al. 2019), of which most belong to the [...]

A new protocol for preparation of tardigrades for scanning electron microscope (SEM) analysis is proposed. The more conventional protocols require various steps and a long time to obtain good drying of water bears, together with specific and uncommon instruments (i.e., critical point dryer) or highly volatile toxic compounds (i.e., hexametildisilazane). The new protocol can be performed using few and simple instruments and materials, all easily accessible, and produces a high yield in terms of dried animals in excellent condition for the observation of external morphological structures with SEM. The acquired data exhibit considerable promise, and the proposed methodology shows potential for application to other meiofaunal groups, including small arthropods, nematodes, and rotifers. Research Highlights: Cheap, safe, and fast new method for Tardigrada preparation for SEM.With the new protocol, the number of animals required for SEM studies is minimized.New protocol is potentially applicable to the study of other meiofaunal soft‐bodied taxa. [ABSTRACT FROM AUTHOR]

Tardigrades are common in many terrestrial environments and habitats. Although little is known on their ecological preferences, previous studies found diversity and community composition significantly affected by various variables. This study associated tardigrade species' records with climatic variables, forest type, and substrate categories exploring tardigrade diversity and species communities to find associations with ecological characteristics of Norwegian forests. A total of 17 473 specimens were identified, encompassing 131 species (including putatively new species) from 305 samples of different substrates (leaf litter, bryophytes, and lichens). Bryophytes and lichens of samples were classified according to the main species, and growth form, and associated with tardigrade species and sample metadata. Tardigrade species' richness was related to climatic variables and forest type, increased with precipitation, decreased with summer temperature, and not varied with precipitation seasonality. Although there was an unbalanced representation of substrate categories in the different forest types, some tendencies were detectable. Mixed oak and birch forests reached the highest species' richness. Tardigrade community composition varied between substrate categories and, to a lesser degree, between forest types, but not with climatic variables. Our study highlights the importance of large-scale variables on tardigrade diversity, and substrate categories for tardigrade community composition. [ABSTRACT FROM AUTHOR]

The genera Xerobiotus and Pseudohexapodibius are xerophilic and characterized by reduced appendages and claws as adaptations to move between small interstices. To increase the knowledge of their biodiversity, biogeography and phylogeny, several specimens from European countries and Australia were analysed using an integrative approach, i.e. morphological, karyological and molecular studies (18S, 28S, cox1 , cytb and ITS2). The phylogenetic position of Xerobiotus with respect to the three evolutionary lineages of Macrobiotus remains unchanged with respect to what was previously identified in the phylogeny of Macrobiotidae. The following new Xerobiotus species are described: Xerobiotus litus sp. nov. Xerobiotus arenosum sp. nov. and Xerobiotus reductus sp. nov. It is proposed that Macrobiotus naginae should be transferred to Xerobiotus (Xerobiotus naginae comb. nov.). Pseudohexapodibius degenerans clusters within Xerobiotus and shares morphological and genetic characters with this genus. Some discrepancies between genetic and phenotypic data are found among the analysed species. Even between the results obtained with analysed genes disagreements are found, with cox1 and cytb generally agreeing with phenotypic results more than ITS2. Genotypic and phenotypic data are useful tools for species identification, but they have to be evaluated critically to obtain reliable results. [ABSTRACT FROM AUTHOR]

Chitin is a structural sugar broadly distributed among all kingdoms, and it is present in Tardigrada as α-chitin. Its presence in the buccopharyngeal apparatus of tardigrades was confirmed in previous studies and associated with autofluorescence emission, and within this emission three components were identified. This study aimed to localize the chitin in the buccopharyngeal apparatus and to understand the nature of the other autofluorescent components. Calcofluor white staining of three tardigrade species (Echiniscus sp. Milnesium sp. Macrobiotus sp.) allowed the chitin localization in the feeding structures and the separation of its signal from the whole autofluorescence emission via confocal laser scanning microscopy. Comparing different fluorochromes found in tardigrades and in the nematode Panagrellus pycnus , lambda and square lambda analyses showed that part of the autofluorescent signal is imputable to a collagen-like compound. The images acquired were analysed for morphological, functional, and evolutionary purposes. Chitin and the other autofluorescent compound were localized in the structures of the buccopharyngeal apparatus. Their distribution highlighted the presence of different levels of 'flexibility/strength' of the structures providing better understanding of their mechanical properties and relating them to the characteristics of the three major limnoterrestrial clades of the phylum Tardigrada. [ABSTRACT FROM AUTHOR]

The Antarctic region has been experiencing some of the planet's strongest climatic changes, including an expected increase of the land temperature. The potential effects of this warming trend will lead ecosystems to a risk of losing biodiversity. Antarctic mosses and lichens host different microbial groups, microarthropods and meiofaunal organisms (e.g., tardigrades, rotifers). The eutardigrade Acutuncus antarcticus is considered a model animal to study the effect of increasing temperature due to global warming on Antarctic terrestrial communities. In this study, life history traits and fitness of this species are analyzed by rearing specimens at two different and increasing temperatures (5°C vs. 15°C). Moreover, the first transcriptome analysis on A. antarcticus is performed, exposing adult animals to a gradual increase of temperature (5°C, 10°C, 15°C, and 20°C) to find differentially expressed genes under short- (1 day) and long-term (15 days) heat stress. Acutuncus antarcticus specimens reared at 5°C live longer (maximum life span: 686 days), reach sexual maturity later, lay more eggs (which hatch in longer time and in lower percentage) compared with animals reared at 15°C. The fitness decreases in animals belonging to the second generation at both rearing temperatures. The short-term heat exposure leads to significant changes at transcriptomic level, with 67 differentially expressed genes. Of these, 23 upregulated genes suggest alterations of mitochondrial activity and oxido-reductive processes, and two intrinsically disordered protein genes confirm their role to cope with heat stress. The long-term exposure induces alterations limited to 14 genes, and only one annotated gene is upregulated in response to both heat stresses. The decline in transcriptomic response after a long-term exposure indicates that the changes observed in the short-term are likely due to an acclimation response. Therefore, A. antarcticus could be able to cope with increasing temperature over time, including the future conditions imposed by global climate change. [ABSTRACT FROM AUTHOR]

Long‐term environment acidifications due to decrease pH of the rainwaters affect both soils and water bodies. The organisms most likely to be affected by acid rain are the ones that possess vital organs made of calcium carbonate; among them are tardigrades, presenting aragonite piercing stylets in feeding apparatuses. A positive relationship between acidic rainfall and loss of tardigrades diversity has been already shown, but there is lack of knowledge of its lethal and sublethal effects. This study quantifies the effects of the acute exposure of three eutardigrade, Acutuncus antarcticus, Hypsibius exemplaris, and Macrobiotus cf. hufelandi, to synthetic acid rains and to organic and inorganic acids (hydrochloric, acetic, sulfuric, and nitric acids) naturally occurring in the environment. The cumulative proportion of dead animals in respect of exposition time was fitted to cumulative Weibull Distribution using a Bayesian framework. At the end of the experiments, animals were observed to investigate damages to their piercing stylets. Besides, stylets were finely morphologically described with Scanning Electron Microscopy. This study shows that acid rains and the other tested acids negatively affect tardigrades accordingly with pH, time of exposure, and tardigrade species. Freshwater species show a better resistance to acidity than the moss dwelling species, which can better acclimate over the time to low pH. The stylets resulted unaltered in almost all of the alive specimens. The results suggest that the tested tardigrades taxa have the ability to buffer the environmental proton change and the negative effect on their populations could be counteracted. Research Highlights: Tardigrades exhibit differential sensitivity toacids.Aragonite piercing stylets of feeding apparatus exposed to acids.Tardigrades can to moderate/high acidity [ABSTRACT FROM AUTHOR]

The peculiar family Murrayidae, comprising the genera Murrayon, Dactylobiotus and Macroversum , contains relatively rare species living in hydrophilic and freshwater habitats on all continents, and contains two of the six exclusively freshwater tardigrade genera. This family probably represents an example of the evolution and persistence of an asexual lineage that differentiated into several taxa without sexual reproduction. Analyses of nuclear and mitochondrial genes (18S , 28S , ITS2 and cox1), and the increase of five taxa to the phylogenetic analyses of Murrayidae led us to infer that Murrayon is polyphyletic, being composed of two 'species groups' that also find morphological supports: the ' dianeae group' characterised by peculiar egg processes (rod-shaped and covered with a cuticular layer), animals with large, evident epicuticular pillars and small claws; and the ' pullari group' characterised by conical egg processes, animals with very small epicuticular pillars, and proportionally larger and longer claws. This latter group is a sister group to Dactylobiotus. Murrayon hastatus is the only species within the genus that has an uncertain position with eggs of the ' dianeae group' and animals of the ' pullari group'. We propose the erection of Paramurrayon gen. nov. (for the ' dianeae group' of species), the emendation of Murrayon , and new taxonomic keys for both genera. Possible scenarios of the evolution of taxa within Murrayidae are hypothesised based on synapomorphic characters. Paramurrayon meieri sp. nov. from Norway is described with an integrative approach. Photographs of type material of Murrayon stellatus, Murrayon nocentiniae, Murrayon ovoglabellus and Macroversum mirum are shown for the first time, together with descriptions of new characters. Murrayon hibernicus is considered as nomen dubium and Murrayon hyperoncus is transferred to Macrobiotus pending further analyses. [ABSTRACT FROM AUTHOR]

Simple Summary: Tardigrades are small micrometazoans able to resist several environmental stresses in any stage of their life cycle. The integrated molecular and morphological analysis of tardigrade specimens collected in Tsukuba (Japan) revealed that this population represents a new species, Macrobiotus kyoukenus sp. nov., belonging to the genus Macrobiotus, one of the most speciose and widespread water bear taxon. The stress resistance capabilities of M. kyoukenus sp. nov. have been tested by submitting animals to extreme desiccation, rapid freezing, and high levels of ultraviolet radiations (UVB and UVC). Animals were able to survive desiccation and freezing, and both hydrated and desiccated animals showed a high tolerance to increasing UV radiations. Overall, our findings contribute to the discovery of a larger tardigrade biodiversity in Japan, and the tolerance capabilities of M. kyoukenus sp. nov. show that this new species could become an emerging model for stress resistance studies. Tardigrades are small micrometazoans able to resist several environmental stresses in any stage of their life cycle. An integrated analysis of tardigrade specimens collected in Tsukuba (Japan) revealed a peculiar morphology and a new sensory field in the cloaca. Molecular taxonomy and phylogenetic analysis on different genes (COI, ITS2, 18S and 28S) confirmed that this population is a new species, Macrobiotus kyoukenus sp. nov., belonging to the widespread Macrobiotus hufelandi group. The stress resistance capabilities of M. kyoukenus sp. nov. have been tested by submitting animals to extreme desiccation, rapid freezing, and high levels of ultraviolet radiations (UVB and UVC). Animals were able to survive desiccation (survivorship 95.71 ± 7.07%) and freezing up to −80 °C (82.33 ± 17.11%). Both hydrated and desiccated animals showed a high tolerance to increasing UV radiations: hydrated animals survived to doses up to 152.22 kJ m−2 (UVB) and up to 15.00 kJ m−2 (UVC), while desiccated specimens persisted to radiations up to 165.12 kJ m−2 (UVB) and up to 35.00 kJ m−2 (UVC). Present data contribute to the discovery of a larger tardigrade biodiversity in Japan, and the tolerance capabilities of M. kyoukenus sp. nov. show that it could become a new emerging model for stress resistance studies. [ABSTRACT FROM AUTHOR]

Anhydrobiosis, a peculiar adaptive strategy existing in nature, is a reversible capability of organisms to tolerate a severe loss of their body water when their surrounding habitat is drying out. In the anhydrobiotic state, an organism lacks all dynamic features of living beings since an ongoing metabolism is absent. The depletion of water in the anhydrobiotic state increases the ionic concentration and the production of reactive oxygen species (ROS). An imbalance between the increased production of ROS and the limited action of antioxidant defences is a source of biomolecular damage and can lead to oxidative stress. The deleterious effects of oxidative stress were demonstrated in anhydrobiotic unicellular and multicellular organisms, which counteract the effects using efficient antioxidant machinery, mainly represented by ROS scavenger enzymes. To gain insights into the dynamics of antioxidant patterns during the kinetics of the anhydrobiosis of two tardigrade species, Paramacrobiotus spatialis and Acutuncus antarcticus, we investigated the activity of enzymatic antioxidants (catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase) and the amount of non-enzymatic antioxidants (glutathione) in the course of rehydration. In P. spatialis, the activity of catalase increases during dehydration and decreases during rehydration, whereas in A. antarcticus, the activity of superoxide dismutase decreases during desiccation and increases during rehydration. Genomic varieties, different habitats and geographical regions, different diets, and diverse evolutionary lineages may have led to the specialization of antioxidant strategies in the two species. [ABSTRACT FROM AUTHOR]

The temperature experienced by micro-invertebrates in extreme environments (such as those of Antarctica) is a pivotal parameter regarding these animals' ecology and physiology. However, at present, detailed knowledge of microhabitat physical conditions in Antarctica is limited, as well as being biased towards sub-Antarctic and Maritime Antarctic regions. To better understand the temperature conditions experienced in the microhabitats of Continental Antarctica by the native microfauna, we recorded temperatures year round in ponds and soils in an area of the Victoria Land coast and compared these measurements with air temperature data from the closest automatic weather station. We identified an important difference in temperature dynamics between the air, soil and pond datasets. Ponds were the warmest sites overall, differing by up to 7.5°C in comparison with the air temperature due to their greater thermal capacity, which also drove their patterns of freeze-thaw cycles and mean daily thermal excursion. [ABSTRACT FROM AUTHOR]

Halyomorpha halys (Stål, 1855) is an invasive agricultural pest in North America and Europe.Most of the information on H. halys predators in invaded areas comes from North America. This work focused on the molecular identification of arthropod predator species capable of feeding on H. halys in northern Italy. Predatory arthropods were collected in the field in four urban parks using the tree‐beating technique. A real‐time PCR workflow was applied to detect H. halys DNA from the gut content of predators.Of the 190 predator individuals analysed, 46 were positive for H. halys DNA and belonged to 10 insect taxa (1 Dermaptera, 3 Coleoptera, 2 Hemiptera and 4 Orthoptera) and six arachnid taxa (2 Opiliones and 6 Araneae).The integration of gut content analysis with laboratory bioassays and field observations allows the identification of a greater number of predators and therefore a better understanding of how the invaded ecosystem is responding to the introduction of a new species, given that samples are taken from the invaded environment itself. Therefore, the gut content analysis provides essential elements for conservation biocontrol in integrated pest management programmes. [ABSTRACT FROM AUTHOR]

Understanding how different taxa respond to global warming is essential for predicting future changes and elaborating strategies to buffer them. Tardigrades are well known for their ability to survive environmental stressors, such as drying and freezing, by undergoing cryptobiosis and rapidly recovering their metabolic function after stressors cease. Determining the extent to which animals that undergo cryptobiosis are affected by environmental warming will help to understand the real magnitude climate change will have on these organisms. Here, we report on the responses of tardigrades within a five-year-long, field-based artificial warming experiment, which consisted of 12 open-top chambers heated to simulate the projected effects of global warming (ranging from 0 to 5.5°C above ambient temperature) in a temperate deciduous forest of North Carolina (USA). To elucidate the effects of warming on the tardigrade community inhabiting the soil litter, three community diversity indices (abundance, species richness, and Shannon diversity) and the abundance of the three most abundant species (Diphascon pingue, Adropion scoticum, and Mesobiotus sp.) were determined. Their relationships with air temperature, soil moisture, and the interaction between air temperature and soil moisture were tested using Bayesian generalized linear mixed models. Despite observed negative effects of warming on other ground invertebrates in previous studies at this site, long-term warming did not affect the abundance, richness, or diversity of tardigrades in this experiment. These results are in line with previous experimental studies, indicating that tardigrades may not be directly affected by ongoing global warming, possibly due to their thermotolerance and cryptobiotic abilities to avoid negative effects of stressful temperatures, and the buffering effect on temperature of the soil litter substrate. [ABSTRACT FROM AUTHOR]

Aim: The long history of isolation of the Antarctic continent, coupled with the harsh ecological conditions of freezing temperatures, could affect the patterns of genetic diversity in the organisms living there. We aim (a) to test whether such pattern can be seen in a mitochondrial marker of bdelloid rotifers, a group of microscopic aquatic and limno‐terrestrial animals and (b) to speculate on the potential mechanisms driving the pattern. Location: Focus on Antarctica. Taxon: Rotifera Bdelloidea. Methods: We analysed different metrics of genetic diversity, also spatially explicit ones, including number of haplotypes, accumulation curves, genetic distances, time to the most recent common ancestor, number of independently evolving units from DNA taxonomy, strength of the correlation between geographical and genetic distances, population genetics neutrality and differentiation indices, potential historical processes, obtained from an extensive sample of cytochrome oxidase subunit I (COI) sequences obtained from bdelloid rotifers. We included 2242 individuals from 23 species in a comparison between Antarctic and non‐Antarctic taxa, correcting for sample size directly in the analyses and then by confirming the results also using only a restricted dataset of nine well‐sampled species. Results: Antarctic species had consistently lower genetic diversity and potential younger relative age than non‐Antarctic species, even if they were similar in sample size, geographical extent, neutrality and differentiation indices, and correlation between genetic and geographical distances. Main conclusions: The extensive survey of genetic diversity in one mitochondrial marker in Antarctic bdelloids supports previous suggestions from other organisms that the origin and maintenance of terrestrial Antarctic fauna are different from those of other continents. Such differences could be speculated to be due, in the case of bdelloid rotifers, to the more recent origin of the species living there in comparison to non‐Antarctic species. [ABSTRACT FROM AUTHOR]

The cuticle is the tardigrade exoskeleton that, limiting animal growth, needs to be periodically shed. New cuticles must be formed (within the old ones) before getting rid of the obsolete exoskeletons at the end of moulting process. After ecdysis (the release of the old cuticle), the exuvia has different destinies according to tardigrade evolutionary lines. In the marine tardigrades (Heterotardigrada), the exuvia is lost and useless, while in the other taxa, it acquires interesting uses to be considered exaptations, since the cuticle previously shaped by natural selection for a function (i.e. as exoskeleton) is coopted for new adaptive scopes. These are related to egg deposition, parental care, mating, and diapause. Egg deposition within the exuvia is one of the three different egg deposition strategies developed by tardigrades: smooth eggs can be laid freely or within the exuvia, while ornamented eggs are laid freely. A new scenario for the evolution of such egg deposition strategies is characterised by five schematic steps: smooth eggs laid freely (ancestral state), synchronization of egg maturation with moulting (developed in tardigrade ancestor in sea), use of the exuvia for oviposition (for enhanced mechanical and physiological egg protection), acquisition of egg ornamentation, and ornamented eggs laid freely (related to a risk-spreading strategy). An interesting thanatochresis case related to the release of free eggs in crustaceans exuviae, convergently developed in two distant taxa of eu- and heterotardigrades, is presented and discussed. [ABSTRACT FROM AUTHOR]

The integration of morphological data and data from molecular genetic markers is important for examining the taxonomy of meiofaunal animals, especially for eutardigrades, which have a reduced number of morphological characters. This integrative approach has been used more frequently, but several tardigrade taxa lack molecular confirmation. Here, we describe Crenubiotus ruhesteini sp. nov. from the Black Forest (Germany) integratively, with light and electron microscopy and with sequences of four molecular markers (18S, 28S, ITS2, cox1 genes). Molecular genetic markers were also used to confirm the recently described Crenubiotus genus and to establish its phylogenetic position within the Macrobiotoidea (Eutardigrada). The erection of Crenubiotus and its place in the family Richtersiidae are confirmed. Richtersiidae is redescribed as Richtersiusidae fam. nov. because its former name was a junior homonym of a nematode family. [ABSTRACT FROM AUTHOR]