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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.

We present a data set on Antarctic biodiversity for the phylum Rotifera, making it publicly available through the Antarctic Biodiversity Information facility. We provide taxonomic information, geographic distribution, location, and habitat for each record. The data set gathers all the published literature about rotifers found and identified across the Continental, Maritime, and Subantarctic biogeographic regions of Antarctica. A total of 1455 records of rotifers in Antarctica found from 1907 to 2018 is reported, with information on taxonomic hierarchies, updated nomenclature, geographic information, geographic coordinates, and type of habitat. The aim is to provide a georeferenced data set on Antarctic rotifers as a baseline for further studies, to improve our knowledge on what has been considered one of the most diverse and successful groups of animals living in Antarctica.

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]

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]