Abundance Of Tardigrades Research Articles

A first look into moss living tardigrades in boreal peatlands.

Tardigrades (Tardigrada) are a phylum of micrometazoans found in all biomes on Earth, but their ecology and habitat preferences remain vastly understudied. Boreal peatlands include a diversity of habitat types and high structural heterogeneity that represents an interesting system to study some of the poorly known habitat preferences of tardigrades. Here, we investigate for the first time tardigrade communities in peatland mosses and the latter's potential associations with key environmental variables. We collected 116 moss samples from 13 sites representing different peatland types and management histories. We found that tardigrades are common and diverse in boreal peatlands, as tardigrades were present in 72% of the collected samples and we identified 14 tardigrade genera. Tardigrade abundance seemed to increase alongside the increasing tree basal area and the density was higher in the microtopographic level further from the water table level, that is, hummocks (mean 117/moss gram) than in lawns/hollows (mean 84/moss gram). Furthermore, the highest tardigrade density was found in the moss taxa that are associated with forested peatland types (i.e., feather mosses) (321 mean/moss gram). Finally, we found interesting patterns regarding tardigrade functional diversity, as carnivorous tardigrades were found only in peatlands with tree basal area > 20 m2 and mostly in hummocks. Our study demonstrates that the habitat heterogeneity of peatlands (e.g., variation in moisture and vegetation cover) represents an interesting system to study tardigrade ecology and habitat preferences. However, since we found variation in tardigrade abundance and communities across peatland types and microhabitats within peatlands, our results highlight that such studies should be conducted with numerous replicate samples and a systematic study design that properly addresses the habitat heterogeneity between and within different peatland types.

Tardigrade distribution in soils of high Arctic habitats.

Tardigrades are omnipresent microfauna with scarce record on their ecology in soils. Here, we investigated soil inhabiting tardigrade communities in five contrasting polar habitats, evaluating their abundance, diversity, species richness, and species composition. Moreover, we measured selected soil physico-chemical properties to find the drivers of tardigrade distribution among these habitats. In spite of reported tardigrade viability in extreme conditions, glacier forelands represented a habitat almost devoid of tardigrades. Even dry and wet tundra with soil developing for over more than 10000 years held low abundances compared to usual numbers of tardigrades in temperate habitats. Polar habitats also differ in species composition, with Diaforobiotus islandicus being typical species for dry and Hypsibius exemplaris for wet tundra. Overall, tardigrade abundance was affected by the content of nutrients as well as physical properties of soil, i.e. content of total nitrogen (TN), total organic carbon (TOC), stoniness, soil texture and the water holding capacity (WHC). While diversity and species composition were significantly related to soil physical properties such as the bulk density (BD), soil texture, stoniness, and WHC. Physical structure of environment was, therefore, an important predictor of tardigrade distribution in polar habitats. Since many studies failed to identify significant determinants of tardigrade distribution, we encourage scientists to include physical properties of tardigrade habitats as explanatory variables in their studies.

The structure of tardigrade communities at fine spatial scales in an Andean Polylepis forest

ABSTRACT Little is known about distribution patterns of micrometazoan organisms at different spatial scales and the mechanisms driving these patterns across different environments. Here we explore the fine-scale structure of tardigrades in a high-elevation Polylepis forest in northern Ecuador. To investigate spatial patterns of tardigrade abundance, we collected samples from different bryophyte taxa (hosts) on the woodland floor. We identified some tardigrades to species, but most taxa were considered at the level of morphological operational taxonomic units. Tardigrade assemblages differed in composition between host taxa, with some tardigrade taxa associated more with certain hosts, which might relate to host architecture or chemistry. Tardigrade occupancy, richness and abundance varied considerably between samples, and we estimate that more than 50 samples are required to estimate tardigrade taxon richness in this forest habitat. Physical distance between samples was not related to similarity of composition, and it seems that fine-scale differences in environmental conditions (including the distribution of host bryophytes) is much more important in determining tardigrade composition. We conclude that standardised, comprehensive sampling of terrestrial tardigrades at fine scales is necessary before making broader comparisons at coarser geographical scales. Such sampling should account for the diversity of potential hosts, with sufficient replication to capture tardigrade diversity.

Tardigrade abundance in relation to urbanisation and highly anthropogenic substrates

Abstract Animals colonising urban environments are exposed to a series of novel stressors and ecological challenges, which can result in adaptations to alternative urban niches. Tardigrades are cosmopolitan invertebrates present in all types of ecosystems, including urban environments; and they can survive under extreme conditions, including periods of desiccation, thus allowing them to colonise novel harsh habitats. Tardigrades are thus a promising model to investigate the challenges and opportunities encountered by urban colonisers. Our aims were 1, to determine if tardigrade abundance in natural substrates (moss, lichen and leaf litter) differs between rural and urban sites and 2, to assess if tardigrades have successfully colonised urban substrates that are highly anthropogenic (road sediment, and material accumulated under cars and in wall crevices). Among natural substrates, we found fewer tardigrades in Cork city than in rural sites. However, in urban sites we found no differences between the number of tardigrades present in natural and anthropogenic substrates. In fact, the highest tardigrade abundances in urban samples were found in abiotic material accumulated in wall crevices. We conclude that even though urbanisation may restrict tardigrade abundance, this group of organisms can successfully colonise alternative urban substrates. More research is needed on the ability of tardigrades and other taxa to inhabit highly unusual and disturbed urban substrates effectively, and the adaptations that may take place when animals colonise such substrates.

Seabirds modify trophic groups, while altitude promotes xeric-tolerant species of Tardigrada in the high Arctic tundra (Svalbard archipelago)

In the Arctic, especially in the coastal mountainous areas, gradual changes in elevation above sea level and allochthonous nutrients delivered by seabirds modify environmental conditions. Increasing elevation affects temperature whereas allochthonous nutrients delivered by seabirds to the terrestrial ecosystem remarkably influence primary production and diversity of organisms. Knowing the abundance of ubiquitous tardigrades (a microinvertebrate phylum), their multitrophic level function and their trophic composition might be essential for understanding ecosystem functioning and matter flow in fragile polar ecosystems. In this study, we tested the effects of altitude and seabird guano on modifying trophic diversity of tardigrades. We found that the tardigrades in Hornsund were herbivorous and microbivorous species dominated. Microbivores were significantly more abundant in guano-supplied than in control areas, which may be explained by the presence of higher nutrient and organic matter content in comparison with areas not fertilised by birds. We observed no significant relationship between the abundance of tardigrade trophic groups and altitude. However, the abundance of xeric-tolerant herbivorous terrestrial tardigrades representing the class Heterotardigrada increased with altitude. Strongly hygrophilic conditions (ponds, swamps, streams) at lower elevations as well as acidic conditions formed by seabird guano may reduce the abundance of heterotardigrades. Our study shows that seabirds rather than the effect of altitude or the generally predicted increasing temperatures in the Arctic, are affecting high Arctic tundra limno-terrestrial invertebrate trophic groups proportion. Our results provide baseline data for future studies of the Hornsund region, since climate change scenarios predict decreased guano delivery by seabirds on mountain slopes, shifts in plant species dominance and more intense fertilisation of lakes by geese, all of which may alter invertebrate trophic composition in southern Svalbard.

Tardigrades in the Canopy: Using Double Rope Techniques to Conduct Sampling Along Vertical Transects

The methods called Double-rope techniques (DRT) were used to sample vertical transects into the temperate forest canopy, to determine the diversity and abundance of tardigrades. This technique is reputedly the safest method of accessing canopies and it uses a minimum of technical hardware. In this case, DRT served to facilitate the access of mobility-limited students into the forest canopy, thereby providing an inspiring experience in field biology for this underserved group as well as allowing replicated point sampling of organisms throughout the treetops.

Deep-Water Tardigrada of the Istanbul Strait’S (Bosporus) Outlet Area of the Black Sea

The results of investigations of tardigrades (2009-2010) in the Bosporus outlet area of the Black Sea are represented. For the first time two species of tardigrades Dipodarctus subterraneus (Renaud-Debyser, 1959) and Tanarctus ramazzottii (Renaud-Mornant, 1975) are recorded for the Black Sea. Tardigrades are registered on 4 stations at depths range 88-250 m. Average abundance of tardigrades widely varied from 141 to 11 440 ind./m2. The vertical distribution of tardigrades in the sediments was analyzed: most specimens (up to 98 %) found in the top 0-1 cm sediment layer.

Tardigrades of Alaska: distribution patterns, diversity and species richness

During the summer of 2010, a biotic survey of tardigrades was conducted along a latitudinal transect in central Alaska from the Kenai Peninsula, via Fairbanks and the Arctic Circle to the coastal plain. Work was centred at the Toolik and Bonanza Creek Long Term Ecological Research Network sites and supplemented by opportunistic collections from the Kenai Peninsula and Anchorage areas. The 235 samples collected at 20 sites over 10 degrees of latitude yielded 1463 tardigrades representing two classes, three orders, 10 families, 23 genera and 73 species from 142 positive samples. A total of 50 species are new to Alaska, increasing the state’s known species richness to 84. Several environmental metrics, such as pH, substrate, elevation, location and habitat were measured, recorded and analysed along the latitudinal gradient. Contrary to expectations, pH did not appear to be a predictor of tardigrade abundance or distribution. Density and species richness were relatively consistent across sites. However, the assemblages were highly variable within and between sites at only 14-20% similarity. We detected no correlation between species diversity and latitudinal or environmental gradients, though this may be affected by a high (59.9%) occurrence of single-species samples (containing individuals of only one species). Estimates of species richness were calculated for Alaska (118) and the Arctic (172). Our efforts increased the number of known species in Alaska to 84, and those results led us to question the validity of the estimate numbers. Keywords: Tardigrade; Alaska; distribution; latitudinal gradient; pH; species richness (Published: 22 May 2013) Citation: Polar Research 2013, 32 , 18793, http://dx.doi.org/10.3402/polar.v32i0.18793

Horizontal distribution of moisture and Tardigrada in a single moss cushion

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 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 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 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. 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.

Seasonal and Spatial Variation in Diversity and Abundance of Tardigrades in Leaf Litter from Louisiana and Florida

Abstract During 2002–2003, we collected samples of leaf litter (10-cm diameter) from two woodland sites in southwestern Louisiana and one in central Florida. In Louisiana, we collected at four times (autumn, winter, spring, and summer) and in Florida in spring and summer. We divided each sample into two layers, an upper leafy layer (1–2 cm in depth) and a lower layer of humus (1–2 cm in depth). We detected six species of tardigrades in samples from Louisiana and five in samples from Florida. Seasonal variation in density of tardigrades was pronounced at each site. Tardigrades generally were more abundant in the upper layer. Density and diversity of tardigrades in the leaf litter at these sites were less than in mountainous areas of Italy and Tennessee, USA.

Effects of macro and micro-environmental factors on the species richness of terrestrial tardigrade assemblages in an Iberian mountain environment

Tardigrade communities are affected by micro and macro-environmental conditions but only micro-environmental variables, and altitudinal gradients have been studied. We review previous reports of altitudinal effects and evaluate the influence by interacting macro- (climate, soils, biome, and others) and micro-environmental (vegetation, moss and leaf litter) factors on tardigrade assemblages at the Sierra de Guadarrama mountain range (Iberian Central System Mountains, Spain). Terrestrial tardigrade assemblages were sampled using standard cores to collect leaf litter and mosses growing on rocks. General Linear Models were used to examine relationships between Tardigrada species richness and abundance, and macro- and micro-environmental variables (altitude, habitat characteristics, local habitat structure and dominant leaf litter type, and two bioclimatic classifications). Variation partitioning techniques were used to separate the effects of altitude and habitat variation, and to quantify the independent influences of climate and soil, vegetation structure and dominant type of leaf litter. Altitude shows a unimodal relationship with tardigrade species richness, although its effect independent of habitat variation is negligible. The best predictors for species richness were bioclimatic classifications. Separate and combined effects of macro-environmental gradients (soil and climate), vegetation structure and leaf litter type are important determinants of richness. A model including both macro- and micro-environmental variables explained nearly 60% of tardigrade species richness in micro-scale plots. Abundance was significantly related only to soil composition and leaf litter type. Tardigrade abundance was not explained by macro-environmental gradients analysed here, despite a significant correlation between abundance and richness.

Unique Similarity of Faunal Communities across Aquatic–Terrestrial Interfaces in a Polar Desert Ecosystem

Critical transition zones, such as aquatic–terrestrial interfaces, have been recognized as important features in landscape ecology. Yet changes in the community structure of soil and sediment biota across aquatic–terrestrial boundaries remain relatively unstudied. We investigated the community structure of the dominant fauna, namely nematodes, rotifers and tardigrades, across lake sediment–soil transects in three basins in a species-poor, polar desert ecosystem (McMurdo Dry Valleys, Antarctica). We also examined substrate (that is, soil and sediment) properties, including moisture, salinity, carbon, nitrogen and phosphate concentration, across these transects. Differences in faunal community structure and biochemical properties were typically explained by hydrologic basin and the sediment–soil gradient, but not by transects within each basin. Bonney Basin contained the least organic carbon, chlorophyll a, nematodes and taxa, whereas there was little difference in many of these measures between Fryxell and Hoare Basins. Nematode (Scottnema lindsayae and Plectus sp.) and rotifer abundance varied along sediment–soil transects. Scottnema lindsayae, the most abundant and widely distributed soil animal in this ecosystem, increased in abundance from sediments to soils, whereas Plectus sp. and rotifer abundance, and taxa richness (that is, nematodes, rotifers and/or tardigrades), decreased; Eudorylaimus sp. and tardigrade abundance did not differ significantly along the transects. Previous studies of soil biodiversity and faunal abundance in this ecosystem have revealed a positive association between these measures and biogeochemistry, if this holds true for lake sediments, our findings suggest sediments in Lake Bonney experience lower rates of nutrient cycling than either Lakes Fryxell or Hoare. Despite differences in faunal abundances along the sediment–soil transects, taxa occurrence was surprisingly similar in soil and sediment, only S. lindsayae was restricted to soil or the lake shore. In contrast, in other ecosystems, soil community composition differs greatly from lake sediments, suggesting that the observed similarity in species occurrence in both soils and sediments may be unique to Antarctica. This finding might result from the extreme low diversity of this ecosystem, presumably limiting competition among fauna, and thus promoting broad ecological niches. Alternatively, environmental conditions in Antarctica may select for species with broad ecological niches.

Tardigrade Distribution in a Medium-sized City of Central Argentina

The distribution and abundance of tardigrades in the city of General Pico (Argentina) are analyzed from samples collected during autumn and spring 2001. Sample sites included paved urban locations with different traffic intensities, non-paved periurban places, and places with peculiar conditions such as the city industrial area and the bus station. Trees of the same species were selected in each area and from each of them nine subsamples of lichens and/or moss, 11 mm in diameter, were taken with steel corers. The diversity, density and relative abundance of tardigrades was recorded and analyzed. Sampling sites were ordinated and classified with PCA and clustering. The number total of species collected in the research was 5. The maximum number of species per site and per tree was 4. The species recorded were: Echiniscus rufoviridis, Milnesium cf. tardigradum, Ramazzottius oberhaeuseri, Macrobiotus areolatus and an undescribed species of the genus Macrobiotus. The average density was approximately 10 specimens per cm2 and the maximum values reach over 50 specimens per cm2. R. oberhaeuseri and M. cf. tardigradum were the most frequent species. R. oberhaeuseri dominates in periurban areas with high suspension dust and very exposed to the sun. M. cf. tardigradum dominates on paved streets with intense vehicle traffic. Results supported the hypothesis of the relationship between air quality and tardigrade diversity.

Small-scale Spatial Distribution Variability in Terrestrial Tardigrade Populations

Terrestrial tardigrades are often found in the lichens and mosses growing on trees and rocks. The assertion that tardigrades in these habitats are very patchy in their distribution has rarely been backed by quantitative sampling. This study assesses spatial variability in tardigrade populations inhabiting small patches (0.1 cm2 to over 5 cm2) of moss and lichen on trees and rocks at three sites in the United States of America. Tardigrades were collected from four replicate rocks in the Ouachita Mountains of Arkansas, with 30 lichen patches collected on two adjacent boulders and 20 moss patches on a second pair of boulders. In Fort Myers and in Citrus Springs, Florida, 30 lichen patches per tree were collected from two pairs of trees. The tardigrades in each sample were extracted, mounted, identified, and counted. The variation in tardigrade abundance among lichen or moss patches within rocks or trees was very high; the only consistent pattern was that very small patches usually lacked tardigrades. Tardigrade diversity and abundance also varied greatly within sites when lichens and mosses of the same species from different rocks and trees were compared (in the most extreme case one tree had numerous individuals of two tardigrade species present while the other had almost no tardigrades). The results of this quantitative sampling support the assertion that tardigrades are very patchy in distribution. Given the considerable time investment required for the quantitative processing of tardigrade samples, this high spatial variability in tardigrade diversity and abundance requires that researches testing ecological hypotheses about tardigrade abundance check variability before deciding how many samples to take.

Population density and species composition of moss‐living tardigrades in a boreo‐nemoral forest

This study investigates for the first time the tardigrade fauna in a variety of different mosses from a coniferous forest and an adjacent clear‐cut area in southern Sweden. Tardigrades were found in a majority of the samples. Sixteen species were recorded, of which the cosmopolitan species Macrobiotus hufelandi was the far most common. Some mosses, particularly species with “wefts” growth form, contained more tardigrades than other mosses, indicating that growth form may have an impact on tardigrade abundance. Mosses of the same species collected from a forest and from a clear‐cut, respectively, did not show a general trend in the overall abundance of tardigrades, but the forest tended to contain more species. Five species of tardigrades (Murrayon dianae, Isohypsibius sattleri, Platicrista angustata, Diphascon belgicae and Diphascon pingue) never previously reported from Sweden were recorded.

Tardigrades from Australian Marine Caves. With a Redescription of Actinarctus neretinus (Arthrotardigrada)

Several marine caves in Australia have been investigated for meiofauna using a freshwater technique to shock large sediment samples. Several species of nematodes, gastrotrichs, crustaceans, polychaetes and aplacophorans were found, and one new species of kinorhynch has been described. In addition, two new species of loriciferans from marine caves in New South Wales, Australia, are under description. This paper is the second in a series describing the unique meiofauna in submarine caves and inland anchialine caves of Australia. The paper deals with the tardigrade fauna of two caves, Jim's Cave and Fish Rock Cave, both located off the coast of New South Wales. The sediment consists of carbonate sediments (shell-hash to shell-gravel) mixed with organic detritus. The abundance of tardigrades is very low in the two caves, but the species diversity is very high. The following arthrotardigrade genera have already been found: Actinarctus, Batillipes, Dipodarctus, Halechiniscus, Raiarctus, Styraconyx, Tanarctus, Tholoarctus, and Wingstrandarctus. The cave fauna of tardigrades seems not to be related to the well-investigated high energy beach fauna of tardigrades along the East Coast of Australia. Most surprising is the discovery of the species Actinarctus neretinus known from the Italian cave, Grotta Cattedrale, supporting the theory that marine caves serve as refuges for an old Tethyan fauna.

Seasonality, abundance, and microhabitat distribution of meiofauna from a Chickahominy River, Virginia tidal freshwater marsh

Meiofauna were sampled from intertidal pool and vegetative hummock microhabitats at a tidal freshwater marsh on the Chickahominy River, Virginia. Nematodes, ostracods, tardigrades, oligochaetes (Naididae), copepods (Harpacticoida and Cyclopoida), and the sabellid polychaete Manayunkia spp. were numerically dominant in monthly collections. Total meiofaunal densities ranged from 169 individuals 10 cm−2 (low marsh pools, April) to 13832 individuals 10 cm−2 (low marsh hummocks, September). Highest densities of total meiofauna were observed in August–September, coincident with recruitment of oligochaetes and Manyunkia spp. to low marsh hummocks. Nematodes were generally abundant in all seasons and represented 37% of total meiofauna collected. Nematode densities were significantly greater on hummocks (p=0.0001). Ostracods were significantly more abundant in pools, Greatest densities of ostracods were observed in May. Tardigrades were abundant November through March, and September. Significantly greater abundance of tardigrades was observed on hummocks. Harpacticoid copepods were abundant from December through April and cyclopoids were abundant from May through September (low marsh only).

Ecological distribution of moss-dwelling tardigrades on Vancouver Island, British Columbia, Canada

Replicate samples of tardigrades were collected at six altitudes from five mountains on Vancouver Island, British Columbia, Canada, to determine the relationship between species of tardigrades and altitude, and between species of tardigrades and species of mosses in which they were collected. A total of 13 696 tardigrades representing 39 species were collected and identified. Thirty-seven species of mosses were identified. Data were analyzed using principal components analysis and cluster analysis. The results from both multivariate statistical methods indicated that the distribution and abundance of tardigrades were not dependent upon the altitude or moss species.