Numerous evolutionary lineages representing an armoured, limno-terrestrial family Echiniscidae are restricted to high mountainous or polar localities, exhibiting clear cold stenothermic preferences. One such group is the genus Claxtonia, with its type species Claxtonia wendti, originally described from Svalbard and later on reported globally. In this paper, we re-describe this taxon by establishing the neotype from Spitsbergen. We sequenced five genetic markers (18S rRNA, 28S rRNA, ITS-1, ITS-2, and COI) for multiple populations of Claxtonia, including C. mauccii, C. molluscorum, C. wendti, and several potentially new species, collected in the Alps, Andes, Carpathians, Scotland, Iceland, Southern Appalachians, Spitsbergen, Scandinavian Peninsula, Borneo, and the West Indies. The relationships between these species are elucidated thanks to the phylogenetic reconstructions based on nuclear loci. Various Claxtonia species frequently co-occur in mosses and lichens, which hampers delineating their probable geographic ranges. All historical records of C. wendti are questioned in the light of our revision. Delineation of new species within the genus is nipped in the bud due to numerous problems with original species descriptions, unknown intraspecific (including ontogenetic) variability, and the lack of DNA barcodes. Finally, it is hypothesized that Claxtonia potentially comprises two lineages: a cold-stenothermic one and a thermophilic subtropical–tropical one.

Research on the limno-terrestrial Tardigrada fauna of the Sub-Antarctic zone began almost 120 years ago. Here we present an overview of the literature data on the presence of tardigrades on sub-Antarctic islands, including the substrates on which they have been found. From 32 published sources, we found original data on the occurrence of 49 currently valid species on six sub-Antarctic islands/island groups. Of these, 9 species (18%) were originally described from this zone, another 13 species (26%) were described from Continental or Maritime Antarctica, almost half of these species (22 species—45%) were originally described from European localities, and the remaining 5 species (10%) were originally described from South America, Africa, or Australia. The validity of the records of individual species is discussed. We consider the presence of 29 species in the Sub-Antarctic to be doubtful. We ascertained a total of 90 combinations of species and islands or island groups. More than half (64%) of these will require confirmation in the future because we currently consider them doubtful. We can conclude that the tardigrade fauna of the sub-Antarctic islands is only very superficially known, and the occurrence of most species in this zone must be verified.

A new Tardigrada species, Claxtonia goni sp. nov. is described from specimens collected in the central area of the Haleakalā National Park, the island of Maui, Hawaii, U.S.A. The new species and Clx. pardalis (Degma & Schill, 2015) together with several examples of Clx. wendti (Richters, 1903) are the only known Claxtonia species with the plates having an intracuticular pattern resembling that on a leopard’s fur. Claxtonia goni sp. nov. differs from Clx. pardalis in the absence of pores on leg plates, in smaller and uniform pores on dorso-lateral plates, in very unequally spaced teeth in the dentate collar, in lesser ratio of internal cephalic cirrus and lateral cirrus A lengths, and in relatively shorter claws in fourth pair of legs. The differences between the new species and the other congeners as well as Echiniscus species with the same cirri composition and similar cuticular sculpture are also defined. The diagnosis of the genus Claxtonia is amended and three Echiniscus species are transferred into the genus with the proposed new combinations: Claxtonia aliquantilla (Grigarick, Schuster & Nelson, 1983) comb. nov., Clx. mosaica (Grigarick, Schuster & Nelson, 1983) comb. nov. and Clx. nigripustula (Horning, Schuster & Grigarick, 1978) comb. nov..

The phyletic relationships both between and within many of tardigrade genera have been barely studied and they remain obscure. Amongst them is the cosmopolitan Bryodelphax , one of the smallest in terms of body size echiniscid genera. The analysis of newly-found populations and species from the Mediterranean region and from South-East Asia gave us an opportunity to present the first phylogeny of this genus, which showed that phenotypic traits used in classical Bryodelphax taxonomy do not correlate with their phyletic relationships. In contrast, geographic distribution of the analysed species suggests their limited dispersal abilities and seems to be a reliable predictor of phylogenetic affinities within the genus. Moreover, we describe three new species of the genus. Bryodelphax australasiaticus sp. nov. , by having the ventral plate configuration VII:4-4-2-4-2-2-1, is a new member of the weglarskae group with a wide geographic range extending from the Malay Peninsula through the Malay Archipelago to Australia. Bryodelphax decoratus sp. nov. from Central Sulawesi (Celebes) also belongs to the weglarskae group (poorly visible ventral plates VII:4-2-2-4-2-2-1) and is closely related to the recently described Bryodelphax arenosus Gąsiorek, 2018, but is differentiated from the latter by well-developed epicuticular granules on the dorsum. Finally, a new dioecious species, Bryodelphax nigripunctatus sp. nov. , is described from Mallorca and, by the reduced ventral armature (II/III:2-2-(1)), it resembles Bryodelphax maculatus Gąsiorek et al., 2017. The latter species, known so far only from northern Africa, is recorded from Europe for the first time. A taxonomic key to the genus members is also presented.

Tardigrades live in diverse habitats. Fundamental research on tardigrades is based on habitat sampling, sample processing, tardigrade culture and preparation for descriptive microscopy, identification and molecular studies. These methods are described and referenced in this chapter which I hope it will be a starting point especially for new tardigradologists.

The recent re-description of Paramacrobiotus Guidetti, Schill, Bertolani, Dandekar and Wolf, 2009 has inadvertently led to the description of an objective synonym within its subgenera nominal taxa. To resolve this issue, we have re-described both subgenera, and proposed a new substitute name for one subgenus, in line with the International Code of Zoological Nomenclature. Additionally we have confirmed the placement of two recently published Paramacrobiotus species, not included in the last revision, within the respective subgenera established herein.

The list of tardigrade taxa up to a sub-generic level, with the type species of each genus and the numbers of lower taxa in each taxon (known in the end of June 2018) is here presented together with the main environments in which taxa were found. Each listed taxon is characterized by characters common to all lower taxa using predominantly most recent taxa definitions. Taxa definitions were eventually adjusted using original descriptions. This review of tardigrade taxa underlines as taxonomy and systematics of the phylum are continuously updated by researchers and new species are constantly discovered. Currently, there are 1265 species (2 of them fossil) of Tardigrada belonging to 129 genera and 28 families including one fossil.

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.

The aim of the study is to get a representative picture of the diet composition of hoopoes in vineyards as specific man made habitats in Central Europe. Therefore diet composition and its interannual variability and the representativeness of two sampling techniques have been studied in hoopoe nestlings, Upupa epops during two breeding periods. Altogether, 1081 prey items were identified and classified into ca. 90 species, 32 families and 11 orders of invertebrates. Regarding interannual variation, the number of prey items per nestbox did not differ between years in the same nestboxes. A within-nest comparison between the two sampling methods revealed a significant difference in the number of prey items for four categories, namely orthopterans, "other beetles", arachnids and lepidopterans. Comparing the two sampling methods, revealed reversed results regarding the proportion of the main prey categories; e.g. scarabaeid larvae, abundant in the camera samples, were less frequent in faeces, whereas "other beetles" were common in faeces, but were only occasionally detected in the camera recordings. The occurrence of the earthworms in the hoopoe's food is novel. We finally discuss advantages as well as the drawbacks of both methods and the possibility to use both these contrasting, but non-invasive techniques.

A new species of Tardigrada Doyere, 1840, Echiniscus pardalis n. sp., is described from two moss samples collected in the Parco Naturale delle Alpi Marittime (NW Italy). It belongs to the Echiniscus arctomys species-group, but differs from other 49 known members of the group mainly by the irregularly and distantly scattered deep pores on the plates and by a unique subsurface cuticular pattern on the plates, resembling that of a leopard's fur. The new species is most similar to eight species from the arctomys group: E. barbarae Kaczmarek & Michalczyk, 2002, E. crebraclava Sun, Li & Feng, 2014, E. dearmatus Bartos, 1935, E. mosaicus Grigarick, Schuster & Nelson, 1983, E. nigripustulus Horning, Schuster & Grigarick, 1978, E. nobilis Mihelcic, 1967, E. tardus Mihelcic, 1951 and E. vinculus Horning, Schuster & Grigarick, 1978. The differences between the new species and these eight species are thoroughly discussed. They mainly concern the presence/absence and relative size of shallow dimples surrounding individual tubercles, the relative length of cirrus A, the presence/absence of a spine on the first pair of legs, the presence/absence of a spur on the internal/external claws and the number of teeth on the collar of the hind legs. This paper is the first result published on Tardigrada collected during the European Distributed Institute of Taxonomy's in All Taxa Biodiversity Inventories+Monitoring programme.

A new species of Parahelichus Löbl & Smetana, 2006 is described from Laos and Thailand: P. pseudogranulosus. A similar species, P. granulosus Delève, 1974, which was originally described only from a single specimen, is redescribed and morphometric data are provided from 442 specimens from Vietnam and Laos. Habitus views, illustrations of important characters as well as results of morphometric analyses are presented and discussed. Praehelichus sinensis (Fairmaire, 1888) is proposed as a new junior synonym of P. sericatus (Waterhouse, 1881).

Summary: For this paper I analyzed the descriptions of all seventy seven currently known Macrobiotus species with three macroplacoids, with or without a microplacoid, to ascertain if they fit to the morphological diagnosis of the genus Paramacrobiotus Guidetti et al., 2009. Most (sixty three species) differed from the genus Paramacrobiotus characters as they were either members of the Macrobiotus harmsworthi and furciger species groups or did not possess the combination of two unique genus characters (elongated macroplacoids and microplacoid considerably distant from the third macroplacoid, if present). Insufficient descriptions for a further ten species means their taxonomic positions remain unclear. Four Macrobiotus species are transferred to the genus Paramacrobiotus and their new taxonomic position is Paramacrobiotus danielisae (Pilato, Binda & Lisi, 2006) comb. nov., Paramacrobiotus hapukuensis (Pilato, Binda & Lisi, 2006) comb. nov., Paramacrobiotus priviterae (Binda, Pilato, Moncada & Napolitano, 2001) comb. nov. and Paramacrobiotus sklodowskae (Michalczyk, Kaczmarek & Węglarska, 2006) comb. nov.

We carried out a study of the moisture distribution and the horizontal distribution of Tardigrada in a single moss cushion. During one field trip, we collected 25 equal samples (in a square of five rows x five columns) from a growth of the moss Hypnum cupressiforme Hedwig. Using two-way anovas without replications and linear regression analyses, we determined that there was no significant gradient of absolute or relative moisture along the moss slope. We isolated 224 specimens of seven Tardigrada species (Milnesium tardigradum Doyere, 1840, Hypsibius convergens (Urbanowicz, 1925), H. microps Thulin, 1928, Diphascon pingue (Marcus, 1936), Astatumen trinacriae (Arcidiacono, 1962), Macrobiotus hufelandi C.A.S. Schultze, 1833 and Minibiotus sp.) from the 25 samples. Using both chi-square tests of independence and chi-square goodness-of-fit tests as well as by calculations of the coefficients of dispersion, we found that the horizontal distribution of tardigrade specimens in general, as well as the distribution of each species, was aggregated. By contrast, species number was random in the observed moss samples. Based on the comparison of all polynomial regression models (third, second, and first order) with the null model and between each other, the distribution of Tardigrada specimens as a whole as well as the distribution of M. hufelandi was related neither to absolute nor relative amount of water in the moss cushion. Based on these results, we formulated a hypothesis explaining tardigrade heterogeneity in randomly sampled mosses, which stayed unexplained up to now. According to this hypothesis, there are two processes occurring at the same time: (1) random recruitment of specimens or eggs on a substratum and (2) subsequent establishment of their own micro-populations and gradual increase in their density in time of active periods with slow radiating of these micro-populations into the surroundings. The consequences of these processes are (1) larger substrata usually contain more tardigrades than smaller ones and (2) some parts of larger substrata can be without any tardigrades, while other parts can host rich tardigrade population(s); this within-substrate heterogeneity was ascertained for the first time in this investigation. We hypothesize that aggregated Tardigrada distribution in each moss cushion is the most likely reason for the large variability in tardigrade abundance in random samples taken from different moss cushions. Hence, we believe that introduced hypothesis and the resulting consequences have a considerable significance in the ecological studies based on random sampling.

The freezing and desiccation tolerance of 12 Klebsormidium strains, isolated from various habitats (aeroterrestrial, terrestrial, and hydro-terrestrial) from distinct geographical regions (Antarctic — South Shetlands, King George Island, Arctic — Ellesmere Island, Svalbard, Central Europe — Slovakia) were studied. Each strain was exposed to several freezing (−4°C, −40°C, −196°C) and desiccation (+4°C and + 20°C) regimes, simulating both natural and semi-natural freeze-thaw and desiccation cycles. The level of resistance (or the survival capacity) was evaluated by chlorophyll a content, viability, and chlorophyll fluorescence evaluations. No statistical differences (Kruskal-Wallis tests) between strains originating from different regions were observed. All strains tested were highly resistant to both freezing and desiccation injuries. Freezing down to −196°C was the most harmful regime for all studied strains. Freezing at −4°C did not influence the survival of studied strains. Further, freezing down to −40°C (at a speed of 4°C/min) was not fatal for most of the strains. RDA analysis showed that certain Antarctic and Arctic strains did not survive desiccation at +4°C; however, freezing at −40°C, as well as desiccation at +20°C was not fatal to them. On the other hand, other strains from the Antarctic, the Arctic, and Central Europe (Slovakia) survived desiccation at temperatures of +4°C, and freezing down to −40°C. It appears that species of Klebsormidium which occupy an environment where both seasonal and diurnal variations of water availability prevail, are well adapted to freezing and desiccation injuries. Freezing and desiccation tolerance is not species-specific nor is the resilience only found in polar strains as it is also a feature of temperate strains.

A new species, Macrobiotus derkai sp. nov., is described from a moss sample collected in the alpine zone of Sierra Nevada del Cocuy Mts (NE Colombia). It differs from the most similar species, Macrobiotus huziori Michalczyk & Kaczmarek, 2006 mainly in the location of the second macroplacoid and in the dimensions of accessory points on the claws. Eggs of the new species have the same type of areolation as eggs of M. huziori but they differ from the latter in the size and number of processes. The differences between the new species and others having similar number and shape of placoids are discussed. An identification key for these species is also provided. A round depression on the dorsal head cuticle is reported in Tardigrada for the first time. The results of a morphometric analysis of the new species are also given.