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Many vertebrates, both homeo- and poikilothermic, show a significant relationship between body size and environmental temperature. Whether such an association may exist in microscopic invertebrates has been less explored. Therefore, we decided to analyse terrestrial Tardigrada from various habitats worldwide to examine whether these animals reveal any relationship pattern between body size and environmental temperature. Data on minimum, maximum, and mean body sizes were extracted from original descriptions or sometimes from later re-descriptions of the species. Minimum, maximum, and mean temperature data from the type localities of the species were retrieved from WorldClim 2. In general, accounting for geographic and phylogenetic confounding factors, the body size of terrestrial tardigrades decreased as the environmental temperature increased. The same tendency was observed for most of the genera when additional analyses were carried out separately for each genus. This is the first biogeographical analysis demonstrating that terrestrial tardigrades generally conform to the temperature–size rule. [ABSTRACT FROM AUTHOR]

Recently it was purported that autofluorescence (AF) in Paramacrobiotus n. sp. provided protection from UV radiation. If true, this would be the first documentation of an adaptive function for AF in any microscopic animal. We review what is currently known about AF in tardigrades, and we provide the first true colour images of tardigrade fluorescence. To assess the hypothesis of AF as UV protection we measured interspecific variation and intraspecific variation. We found that interspecific variation was much greater than intraspecific variation. We compared the fluorescence emission spectra for nine species of tardigrades, and together with the true colour fluorescence images, we noticed different patterns of fluorescence suggesting a rich diversity of fluorophores. We examined epidermal pigments of a new species of Milnesium and Ramazzottius kretschmanii and found that they are not the source of fluorescence in these species. We suggest further research is necessary to test the hypothesis that AF is UV protective in tardigrades, and we demonstrate and assess four different research tools for examining autofluorescence in microscopic animals. [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]

The cosmopolitan echiniscid genus Hypechiniscus contains exclusively rare species. In this contribution, by combining statistical morphometry and molecular phylogeny, we present qualitative and quantitative aspects of Hypechiniscus diversity, which remained hidden under the two purportedly cosmopolitan species: H. gladiator and H. exarmatus. A neotype is designated for H. gladiator from Creag Meagaidh (Scotland), and an informal re-description is provided for H. exarmatus based on animals from Creag Meagaidh and the Isle of Skye (Inner Hebrides). Subspecies/forms of H. gladiator are suppressed due to the high developmental variability of the cirrus dorsalis. At the same time, four species of the genus are described: H. daedalus sp. nov. from Roan Mountain and the Great Smoky Mountains (Southern Appalachian Mountains, USA), H. flavus sp. nov. and H. geminus sp. nov. from the Yatsugatake Mountains (Honshu, Japan), and H. cataractus sp. nov. from the Malay Archipelago (Borneo and the Moluccas). Dorsal and ventral sculpturing, together with morphometric traits, are shown to be the key characters that allow for the phenotypic discrimination of species within the genus. Furthermore, the morphology of Hypechiniscus is discussed and compared to that of the most similar genera, Pseudechiniscus and Stellariscus. Finally, a diagnostic key to all recognized Hypechiniscus species is provided. [ABSTRACT FROM AUTHOR]

The Central American Isthmus has had profound effects on the evolution and distribution of larger marine organisms, but the impacts on meiobenthic animals have received little attention. Tardigrades are microscopic metazoan lobopodians that are ubiquitous in benthic communities worldwide, but little is known about marine tardigrades in Central America. Only two marine tardigrades have been identified to species level in all of Central America, and these came from a single sample of barnacles from El Salvador collected in 1953. Additionally, multiple haplotypes of Echiniscoides were reported from Costa Rica and Panama, but species names were not assigned. Here we report an extensive survey of both intertidal and subtidal marine tardigrades from both the Caribbean and Pacific coasts of Costa Rica. We found 701 individuals in 65 samples. There was a total of 19 taxa, including seven species with a sufficient quality and quantity of specimens to describe here as new to science. The new species are Archechiniscus murilloi sp. nov., Batillipes homocercus sp. nov., Batillipes ichthyocercus sp. nov., Echiniscoides costaricensis sp. nov., Echiniscoides ritavargasae sp. nov., Styraconyx vargasi sp. nov. and Tanarctus breedyae sp. nov. Ten taxa were found only in the Caribbean, six were found only in the Pacific, and three were found on both coasts. We discuss the three species with trans-isthmus distributions and note two additional candidate geminate species pairs that warrant further investigation. [ABSTRACT FROM AUTHOR]

Background. The phylum Tardigrada consists of over 1,300 species that inhabit terrestrial, freshwater and marine environments throughout the world. In terrestrial habitats they live primarily in mosses, lichens, leaf litter and soil, whereas tardigrades in freshwater and marine environments are mainly found in sediments and on aquatic plants. More than 65 species have been previously reported in the state of Tennessee, USA. Methods. Tardigrades present in moss cushions (Grimmia sp.) collected from a xerothermic habitat on the East Tennessee State University campus, Johnson City, TN, USA, were extracted, mounted on slides, identified, and counted. Additional samples of fresh dried moss were used for integrative analyses, including morphological analysis with phase contrast (PCM) and scanning electron microscopy (SEM), as well as molecular analyses of COI, 18S rRNA, 28S rRNA, and ITS-2 of the Macrobiotus and Milnesium species. Results. Five species were found, including two species new to science: Viridiscus miraviridis sp. nov. and Macrobiotus basiatus sp. nov. Viridiscus miraviridis sp. nov. differs from other members of the genus mainly by having a different type of dorsal cuticle and some other, more subtle, morphometric characters. In addition to the two new species, Viridiscus perviridis and Viridiscus viridissimus were present, and males of Vir. viridissimus were found for the first time, the first record of males in the genus Viridiscus. Macrobiotus basiatus sp. nov. is most similar to Macrobiotus nelsonae, but it differs from Mac. nelsonae mainly by the stylet supports being situated in a more anterior position, shorter and narrower egg processes, and a smaller number of areoles around the egg processes. Moreover, the identification of Milnesium inceptum was confirmed as the first record for the USA by analysis of COI. [ABSTRACT FROM AUTHOR]

A major inventory of tardigrades in the Great Smoky Mountains National Park was conducted and we compared tardigrade species composition in moss and lichen samples and analysed environmental correlates of tardigrade community structure. We also compared these tardigrades with those collected from soil. The basic dataset from tree mosses and lichens consisted of 336 samples, 9200 individuals and 43 species. The supplemental dataset from rock mosses and lichens consisted of 29 samples, 811 individuals, and 41 species. Collectively, there were 57 species present in mosses and lichens. Eleven species were found uniquely on rock habitats. Two-way ANOVAs for various community metrics showed no significant differences between substrate (moss versus lichen) or height (ground level versus breast height); however, there were significant differences between ATBI plots. Tardigrade communities were not significantly different between mosses and lichens, but soil tardigrade communities were quite distinct from these moss/lichen communities. We analysed the impact of 17 environmental variables on community structure using partition tree analyses. SOx deposition explained most of the variation in species richness and evenness in moss tardigrades. Forest disturbance regime had the greatest impact on abundance in lichen tardigrades. Other environmental factors influencing community structure are discussed. [ABSTRACT FROM AUTHOR]

Homeotherms and many poikilotherms display a positive relationship between body size and latitude, but this has rarely been investigated in microscopic animals. We analysed all published records of marine Tardigrada to address whether microscopic marine invertebrates have similar ecogeographical patterns to macroscopic animals. The data were analysed using spatially explicit generalized least squares models and linear models. We looked for latitudinal patterns in body size and species richness, testing for sampling bias and phylogenetic constraints. No latitudinal pattern was detected for species richness, and sampling bias was the strongest correlate of species richness. A hump-shaped increase in median body size with latitude was found, and the effect remained significant for the Northern Hemisphere but not for the Southern. The most significant effect supporting the latitudinal gradient was on minimum body size, with smaller species disappearing at higher latitudes. Our results suggest that biogeographical signals were observed for body size, albeit difficult to detect in poorly studied groups because of swamping from biased sampling effort and from low sample size. We did not find a significant correlation with the latitudinal pattern of body size and ecologically relevant net primary productivity. [ABSTRACT FROM AUTHOR]

Just over 200 species of marine tardigrades have been described, and most of these have been collected in sand and other sediments. However, several species are known to associate with other invertebrates such as barnacles, bryozoans, and holothurians. It is possible that many epizoic tardigrade species remain to be discovered, since surveys of tardigrades on other potential animal hosts are very rare. Sponges, with extensive cavities, constant water flow, and protective secondary compounds, are known to harbour a highly diverse epizoic community, but there are no published studies indicating that marine tardigrades are among this community, and there is only one published record of tardigrades from freshwater sponges. We collected 30 samples of marine sponges, consisting of 12 species, from the central Bahamas. We processed these for tardigrades and other meiofauna using the freshwater shock technique. One unusual non-tardigrade in our samples was Loxosomella sp., an entoproct which is a known commensal on sponges. Here we also provide the first record of marine tardigrades associated with marine sponges. However, we found only one species, Archechiniscus bahamensis, which is the most common species occurring free-living in Bahamian subtidal sand. Therefore, we conclude that marine sponges, at least in the Bahamas, do host epizoic marine tardigrades, but they may not be a unique or important host for marine tardigrades. [ABSTRACT FROM AUTHOR]

Mainly because of the problems with species delineation, the biogeography of microscopic organisms is notoriously difficult to elucidate. In this contribution, variable nuclear and mitochondrial DNA markers were sequenced from individual specimens representing the Echiniscus virginicus complex that are morphologically indistinguishable under light microscopy (five populations from the temperate Eastern Nearctic and 13 populations from the subtropical and tropical zone). A range of methods was used to dissect components of variability within the complex (Bayesian inference, haplotype networks, Poisson tree processes, automatic barcode gap discovery delineations, principal components analysis and ANOVA). We found deep divergence between the temperate Eastern Nearctic E. virginicus and pantropical Echiniscus lineatus in all three genetic markers. In contrast, intraspecific genetic variation was very low, regardless of the geographical distance between the populations. Moreover, for the first time, statistical predictions of tardigrade geographical distributions were modelled. The factor determining the allopatric geographical ranges of deceptively similar species analysed in this study is most likely to be the type of climate. Our study shows that widespread tardigrade species exist, and both geographical distribution modelling and the genetic structure of populations of the pantropical E. lineatus suggest wind-mediated (aeolian) passive long-distance dispersal. [ABSTRACT FROM AUTHOR]

Knowledge of global biodiversity is essential for a basic understanding of Earth's ecosystems and for the conservation of life. Although many estimates of species numbers have been attempted using various techniques, many smaller phyla remain poorly known without such estimates. For most of these it is unclear if they are species-poor or just poorly studied. The phylum Tardigrada is one of these phyla. Specialists have created a regularly updated checklist for the known tardigrade species, which as of 15 July 2013 listed 1190 taxa (species and subspecies). Of these, 1008 are limnoterrestrial and 182 are marine. These were the most up-to-date data at the time of our analysis. As species accumulation curves show little sign of levelling out, they do not provide a useful tool for estimating global tardigrade diversity from existing species numbers. A new technique has recently been developed that uses the more complete knowledge of higher taxonomic levels to estimate the asymptotic number of species. We applied this technique to limnoterrestrial and marine tardigrades. We estimate that the global total for limnoterrestrial tardigrades is 1145 (upper 95% CI = 2101), and the global total for marine tardigrades is 936 (upper 95% CI = 1803). This yields 87% completeness for our knowledge of limnoterrestrial tardigrades, and only 19% completeness for our knowledge of marine tardigrades. Thus, although many more marine species remain to be discovered, it appears that tardigrades are both poorly studied and relatively species poor. [ABSTRACT FROM AUTHOR]

Milnesium, with its relatively short and wide buccal tube, is considered carnivorous. Species in this genus exhibit differences in buccal tube length, standard buccal tube width, and the buccal tube length/width ratio. To determine whether buccal tube size is correlated with the type of prey, ˜4000 specimens of various Milnesium species were examined. Among those with identifiable gut contents, ˜97% contained tardigrades, rotifers, or both, whereas only ˜3% contained nematodes or amoebas. In total, 189 females with guts containing only tardigrades, only rotifers, or both were analysed with general linear model multivariate analysis. Milnesium specimens containing only tardigrade remnants were larger and had longer and wider buccal tubes than those containing only rotifers. Those with only tardigrades in the gut also had a significantly lower buccal tube length to width ratio than those with only rotifers in the gut. Specimens with a mixed diet (rotifers and tardigrades) had intermediate values of buccal tube width and length, and these differed significantly from individuals containing rotifers or tardigrades only. Variation in buccal tube dimensions was linked with interspecific and age (size)-related factors, and differences in buccal tube dimensions associated with gut content remained significant, even when the analysis was controlled for the interspecific variation. No evidence of cannibalism was observed. [ABSTRACT FROM AUTHOR]

Quantitative traits are an important part of tardigrade taxonomy for both heterotardigrades and eutardigrades. Because most quantitative traits vary as a function of body size, variation in body size complicates comparisons between individuals or populations. Thus, body size effects must be eliminated in morphometric analysis. Although ratios (size of character/body size) are often used to attempt this, they only work for the specific case of isometry (i.e. when a structure grows proportionally to body size). Ratios do not eliminate body size effects for allometric (disproportionate) growth. In eutardigrades, body size is highly correlated with the length of the rigid buccal tube, whereas body length (BL) is highly variable because of the flexibility of the cuticle and the orientation and coverslip pressure on the specimen. In heterotardigrades, BL is typically used to indicate body size because the thickened dorsal plates provide more rigidity and reliability in measurements. We measured 27 traits in 97 specimens of Paramacrobiotus tonollii (Eutardigrada) and 14 traits in 100 specimens of Echiniscus virginicus (Heterotardigrada) and found that many traits are allometric rather than isometric. Thorpe (1975, Biol J Linn Soc 7:27) provided a normalization technique to eliminate body size effects for any trait regardless of its relationship to body size. Using the data from P. tonollii, we show that Thorpe's size normalization does successfully remove buccal tube length effects (body size effects), while pt indices generally do not. We also demonstrate the effectiveness of Thorpe's normalization in species delineations of Macrobiotus recens and Macrobiotus hufelandi, two species that differ primarily in a few quantitative traits and overall body size in addition to the eggs. Based on these examples, we propose that the allometric exponent (b) and the Y‐intercept (a*) of the regression of Thorpe normalized traits versus body size are valuable metrics in tardigrade systematics. [ABSTRACT FROM AUTHOR]

The story of the Tardigrada Symposia began 35 years ago in Pallanza, Italy. It was an idea of Professor Livia Tonolli, who wanted to honour Professor Giuseppe Ramazzotti, at that time the authority in that scientific field and her friend. Considering that tardigrades are a neglected group of metazoans (still to date), this particular event could be finished with that occasion, but it has not been so. With some gaps, the meetings have been proceeded till now, promoting scientific exchange among the researchers and improving the research quality. Following these 35 years and the topics of the symposia, we can understand the changing in the scientific approach. Taxonomy and faunal studies were the predominant topics of the first symposium, but also ultrastructural morphology, ecology, physiology, cytotaxonomy and reproductive biology were represented. Furthermore, the studies by SEM moved their first steps in that occasion. Faunal and taxonomic studies represented often the main topic during the years, but also other kinds of researches involving phylogeny, physiology, ultrastructure of organs and cells always accompanied it. From these points of view, often tardigrades were compared with other animal groups, giving a wider sense to the research. Molecular aspects were already considered in the third symposium (1980, Tennessee), but reconsidered only in the symposium in Cambridge (1994) and developed from the symposium in Denmark (2000). The last symposia showed an increased number of participants and scientific contributions. In line with the increasingly international nature of publications, the quality of the proceedings has also increased, always using in the last 10 years qualified international journals with peer review and impact factor, as now required by young scientists to further their careers. [ABSTRACT FROM AUTHOR]

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We studied the St. Croix River from May to September 2000, sampling the water with surface plankton net tows. We found low water, low flow, and a warm environment and observed new surface plankton. We report a red alga. The surface plankton also contained the alga genera Oedegonium, Hydrodictyon, Elakatothrix, Selenastrum, Tetraedon, Quadrigula, and Xanthidinium for the first time in our years of study. We also observed Synura, a chrysophyte, which had not been observed previously. We found many suctorian and amoeboid forms in the plankton, and we report the first continuous surface plankton observations of tardigrades. [ABSTRACT FROM AUTHOR]

Summary1 Tardigrades comprise a micrometazoan phylum that is a sister group of the arthropods. 2 They are components of the meiobenthos in lotic habitats, and ≈ 50–70 species have been reported in such habitats world-wide. Approximately 800 species have been identified from all marine, freshwater, and terrestrial habitats. 3 Taxonomy is based primarily on the morphology of the claws, buccal-pharyngeal apparatus, cuticle and eggs. 4 Reproductive modes include sexual reproduction (amphimixis) and parthenogenesis. The sexual condition of individuals may be either gonochorism, unisexuality, or hermaphroditism. Moulting occurs throughout the life of the tardigrade. 5 Latent states (cryptobiosis, including encystment, anoxybiosis, cryobiosis, osmobiosis and anhydrobiosis) enable tardigrades to withstand unfavourable environmental conditions. 6 Population densities, life histories, dissemination and biogeography of freshwater species are poorly known. [ABSTRACT FROM AUTHOR]

From time to time, small, fragile, previously unknown fossil invertebrates are found in specialized habitats. Occasionally, as in the present case, a fragment of the original habitat that existed millions of years ago is also preserved. The present article describes a previously unknown microinvertebrate in Dominican amber that cannot be placed in any group of extant invertebrates. Placed in a new family, genus, and species, the fossil shares characters with both tardigrades and mites, but clearly belongs to neither group. The several hundred fossil individuals preserved in the amber shared their moist, warm habitat with pseudoscorpions, nematodes, fungi, and protozoa. The large number of fossils provided additional evidence of their biology, including their reproductive behavior, developmental stages, and food. While there is no extant group that can accommodate these fossils, and we have no knowledge of any extant descendants, this discovery shows that unique lineages of minute invertebrates were surviving in the mid‐Tertiary. [ABSTRACT FROM AUTHOR]

One of the largest inventories of tardigrades ever conducted occurred from 20002010 in the Great Smoky Mountains National Park, USA. Over 16,000 specimens were catalogued, 85 species were identified, 11 species new to science were described, and 16 other possible new species await further study. More than 20 papers have resulted from the GSMNP tardigrade inventory, making the Smokies the most thoroughly studied area in North America for tardigrades. Several species lists have been published over this 20-year period, but many taxonomic revisions and new identifications have led to significant changes to the list. Biogeographical studies citing species records from earlier studies could yield serious errors. Here we update the species list from the Smokies to accommodate the many recent changes in tardigrade taxonomy, we re-analyze some species in light of delineations of cryptic species groups that have occurred recently via integrative taxonomy, and we provide a table of all synonyms that have been used in previous publications. We also make available, for the first time, the Smokies tardigrade database, complete with all locations, elevations, and substrates.

This is the first survey of subtidal marine tardigrades from the Bahamas, and we compare our results with earlier studies of Bahamian intertidal habitats. In 2011 and 2014 we collected 60 subtidal sand samples from Bimini, the Berry Islands, New Providence, Eleuthera, and the Exumas. We found 11 species only one of which, Dipodarctus subterraneus (Renaud-Debyser, 1959), had been found in the previous intertidal Bahamian collections. Thus, 10 species are new records for the Bahamas, and four of these are new to science. We describe two of the new species (Archechiniscus bahamensis sp. nov. and Anisonyches eleutherensis sp. nov.). Additional material is needed for a conclusive identification of the undescribed species of Batillipes and Florarctus. Based on examination of the holotype of Anisonyches diakidius Pollock, 1975, we redescribe this species and give an emended diagnosis of the genus and the species. We also provide new keys to the species in the genera Archechiniscus and Anisonyches. A Chao2 species richness estimate indicated that our sampling effort was extensive and probably recovered most common species. Correlations of abundance and diversity indices with regard to depth, distance to nearest shore, and sediment grain size were not significant.

This monograph describes the global records of marine water bears (Phylum Tardigrada). We provide a comprehensive list of marine tardigrades recorded from around the world, providing an up-to-date taxonomy and a complete bibliography accompanied by geographic co-ordinates, habitat, substrate and biogeographic comments. A link is provided to an on-line interactive map where all occurrences for each species are shown. In total we list 197 taxa and their 2240 records from 39 oceans and seas and 18 Major Fishing Areas (FAO). It is hoped this work will serve as a reference point and background for further zoogeographic and taxonomic studies on marine tardigrades.

Five marine arthrotardigrade species are recorded from Moorea, Society Islands, French Polynesia. Four were collected from coral sand; two, Dipodarctus anaholiensis Pollock, 1995 and Florarctus kwoni Chang & Rho, 1997, are new records for the region, and two, Halechiniscus perfectus Schulz, 1955 and Styraconyx kristenseni kristenseni Renaud-Mornant, 1981, have been previously reported. The fifth, a new species Styraconyx turbinarium sp. nov., is described and was collected from the drifting brown alga Turbinaria ornata. The new species is characterized by the presence of peduncles on all digits, an elongate primary clava, and the lateral cirrus A arising from a common pedestal and enveloped by a common membrane extending almost to the claval tip. The new species differs from the most similar species, Styraconyx tyrrhenus D'Addabbo Gallo, Morone De Lucia & de Zio Grimaldi, 1989, by having longer and differently shaped primary clavae which are elongated in the new species and club-shaped in S. tyrrhenus. By having a dorsal cuticle that is coarsely punctated but without folds or other ornamentations, the new species can be easily distinguished from S. craticulus (Pollock, 1983), a species with similar primary clavae, but with cuticular dorsal folds ornamented with a grid-like pattern.

For many decades the genus Milnesium was thought to consist of a single, cosmopolitan species: Milnesium tardigradum Doyère, 1840. However, recently the genus has been re-evaluated, and numerous new species have been described. Currently, over twenty extant species and one fossil are recognised, and most appear to have very narrow geographic ranges. It is doubtful that M. tardigradum sensu stricto is truly cosmopolitan, but to evaluate this hypothesis, specimens previously identified as M. tardigradum must be re-examined using newly proposed taxonomic characters. As part of the All Taxa Biodiversity Inventory (ATBI) we collected Milnesium specimens from various locations in the Great Smoky Mountains National Park (GSMNP). Two Milnesium species have been evaluated, and one of them, Milnesium bohleberi sp. nov., is new to science. The new species is most similar to M. eurystomum but differs by shorter claws and a shorter, narrower, and more cylindrical buccal tube. The other Milnesium species, very rare in our collection, is morphologically indistinguishable from Milnesium granulatum Ramazzotti 1962, which was previously known only from Chile, Italy and Romania. Based on the recently revised description of M. tardigradum sensu stricto, this nominal species for the genus has not been found in the GSMNP samples.

As part of the All Taxa Biodiversity Inventory (http://www.dlia.org), an extensive survey of tardigrades has been conducted in the Great Smoky Mountains National Park (GSMNP) in Tennessee and North Carolina, U.S.A., by Bartels and Nelson. Freshwater tardigrades include three species in the aquatic genus Thulinius (Eutardigrada, Isohypsibiidae). A new species, Thulinius romanoi, described from stream sediment, is distinguished from all other congeners by having a sculptured cuticle. In addition, the presence of Thulinius augusti (Murray, 1907) was verified by combined morphological and molecular analysis, and nine specimens of a third species, Thulinius cf. saltursus, were also found. Thulinius augusti is a new record for the United States. Thulinius saltursus (Schuster, Toftner & Grigarick, 1978) was previously recorded in California and Ohio, but our specimens vary slightly in morphology. The list of tardigrades from streams in the GSMNP was updated to a total of 44 species, 22 of which were predominantly or exclusively aquatic.