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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. [ABSTRACT FROM AUTHOR]

Richtersius coronifer, the nominal species for the family Richtersiidae and a popular laboratory model, exemplifies a common problem in modern tardigrade taxonomy. Despite undeniable progress in the field, many old and incomplete descriptions of taxa hinder both species delimitation and the estimation of species diversity and distribution. Although for over a century this species has been recorded throughout the world, recent research indicates that records to date are likely to represent a species complex rather than a single cosmopolitan species. However, in order to recognise and name species diversity within the complex, an integrative redescription of the nominal species is first needed. Here, we describe an R. coronifer population collected from Spitsbergen, i.e., one of the two localities mentioned in the original description, with detailed morphological and morphometric data associated with standard DNA sequences of four standard genetic markers (18S rRNA, 28S rRNA, ITS-2, and COI) and supported by transcriptome sequencing. We propose replacement of the neotype designated in 1981 by Maucci and Ramazzotti, as it is impossible to verify whether the existing neotype is conspecific with specimens studied by Richters in 1903 and 1904. Finally, using newly obtained cytochrome c oxidase subunit I (COI) sequences of populations from Spitsbergen, Italy, Poland, and Greece together with sequences deposited in GenBank (China, Greenland, Italy, Mongolia), we performed genetic species delimitation, which indicated seven distinct potential species within the genus Richtersius, in addition to the nominal taxon. This study marks a starting point for further research on the taxonomy of and species diversity within the genus. Moreover, this work has the potential to be the first tardigrade redescription to provide both genetic barcodes and a transcriptome of the species in question. [ABSTRACT FROM AUTHOR]

(1) During the Arctic summer, little auks ( Alle alle) deposit considerable amounts of guano on land. Ecosystems subsidised in nutrients are known to hold greater biodiversity and to produce grander biomass of plants and animals compared with areas where seabirds do not nest. (2) The aim of this study was to look into the relationship between guano fertilisation and body size of invertebrates inhabiting tundra. (3) The specimens of Macrobiotus islandicus islandicus Richters, 1904, a tardigrade dwelling in mosses and lichens of the Arctic, from six different populations from Spitsbergen (Hornsund fjord) were measured. Tardigrades were collected from areas different in terms of seabird guano effects on the tundra ecosystem. An overall body size index for tardigrades was calculated using a principal component analysis. (4) Here, we show that the body size of M. i. islandicus is larger in vicinities of the little auk colonies than in areas devoid of bird nesting sites. (5) Given that fitness of many invertebrates is positively correlated with their condition, our study underlines the ecological importance of a side effect of seabirds biology-the transfer of nutrients from the sea to the land. [ABSTRACT FROM AUTHOR]

Two transects were established and sampled along altitudinal gradients on the slopes of Ariekammen (77°01′N; 15°31′E) and Rotjesfjellet (77°00′N; 15°22′E) in Hornsund, Spitsbergen. In total 59 moss, lichen, liverwort and mixed moss–lichen samples were collected and 33 tardigrade species of Hetero- and Eutardigrada were found. The α diversity ranged from 1 to 8 per sample; the estimated number of species based on all analysed samples was 52±17 for the Chao 2 estimator and 41 for the incidence-based coverage estimator. According to the results of detrended canonical correspondence analysis, altitude and type of substratum were the most important factors influencing tardigrade communities in the investigated area. Macrobiotus crenulatus, M. hufelandi hufelandi and Hypsibius pallidus dominated in the lower elevations, whereas Echiniscus wendti and E. merokensis merokensis prevailed in samples from higher plots. Macrobiotus islandicus islandicus was collected most often from mosses collected from rock whereas Isohypsibius coulsoni from mosses collected from soil. Analyses of covariance were employed to test for differences in species richness between the transects in relation to altitude. Contrary to expectations, there were significant differences in species richness between the transects, but richness was not significantly related to altitude. Interestingly, significant effects of colonies of seabirds, little auk (Alle alle), on the tardigrades communities were detected. Additionally, in one of the samples first ever males of Milnesium asiaticum were found. Their measurements and microphotographs are provided herein. [ABSTRACT FROM AUTHOR]