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This is the first survey of marine tardigrades from the British Virgin Islands, though two species were previously reported from St. Croix, U.S. Virgin Islands. In June 2016, we collected subtidal and intertidal sand samples from various locations throughout the British Virgin Islands. We found 602 tardigrades in 18 of 21 samples, and these included 12 taxa, one of which, Batillipes wyedeleinorum sp. nov., is new to science and described here. We compared abundance and species diversity in intertidal and subtidal samples and found significantly greater abundance in intertidal habitats but no significant difference in the number of observed species between the two habitats. We calculated Chao 1 species richness, which indicated higher estimated richness in intertidal habitats and 15 ± 3.7 species (x̅ ± SD) in both habitats combined. Non-metric Multidimensional Scaling revealed differences in species composition between the two habitats with some species showing clear preferences for one or the other. [ABSTRACT FROM AUTHOR]

Ranges of tardigrade intraspecific and interspecific variability are not precisely defined, both in terms of morphology and genetics, rendering descriptions of new taxa a cumbersome task. This contribution enhances the morphological and molecular dataset available for the heterotardigrade genus Viridiscus by supplying new information on Southern Nearctic populations of V.perviridis, V.viridianus, and a new species from Tennessee. We demonstrate that, putting aside already well-documented cases of significant variability in chaetotaxy, the dorsal plate sculpturing and other useful diagnostic characters, such as morphology of clavae and pedal platelets, may also be more phenotypically plastic characters at the species level than previously assumed. As a result of our integrative analyses, V.viridianus is redescribed, V.celatus sp. nov. described, and V.clavispinosus designated as nomeninquirendum, and its junior synonymy with regard to V.viridianus suggested. Morphs of three Viridiscus species (V.perviridis, V.viridianus, and V.viridissimus) are depicted, and the implications for general echiniscid taxonomy are drawn. We emphasise that taxonomic conclusions reached solely through morphological or molecular analyses lead to a distorted view on tardigrade α-diversity. [ABSTRACT FROM AUTHOR]

To persist in extreme environments, some meiofaunal taxa have adopted outstanding resistance strategies. Recent years have seen increased enthusiasm for understanding extreme-resistance mechanisms evolved by tardigrades, nematodes and rotifers, such as the capability to tolerate complete desiccation and freezing by entering a state of reversible suspension of metabolism called anhydrobiosis and cryobiosis, respectively. In contrast, the less common phenomenon of diapause, which includes encystment and cyclomorphosis, is defined by a suspension of growth and development with a reduction in metabolic activity induced by stressful environmental conditions. Because of their unique resistance, tardigrades and rotifers have been proposed as model organisms in the fields of exobiology and space research. They are also increasingly considered in medical research with the hope that their resistance mechanisms could be used to improve the tolerance of human cells to extreme stress. This review will analyse the dormancy strategies in tardigrades, rotifers and nematodes with emphasis on mechanisms of extreme stress tolerance to identify convergent and unique strategies occurring in these distinct groups. We also examine the ecological and evolutionary consequences of extreme tolerance by summarizing recent advances in this field. [ABSTRACT FROM AUTHOR]

An All Taxa Biodiversity Inventory (ATBI) is underway in the Great Smoky Mountains National Park (GSMNP), with the goal of attempting to identify all species of life in the 2000 km2 park. The GSMNP is a hotbed of biodiversity, a U.N. Biosphere Reserve, and one of the largest protected, deciduous forests in the temperate world. We have completed two field seasons of work on the tardigrades in the park (2001–2002). As of July 2003, we have collected 420 samples from soil/decomposed leaf litter, lichens and mosses on trees, and stream sediment and periphyton. A few samples from caves, bird nests, and lichens/mosses on rocks were also collected. Samples were taken from within permanent plots established for the ATBI, representing the major biological communities of the GSMNP. Tardigrades were extracted from samples using centrifugation with Ludox AM™, individually mounted on microscope slides in Hoyer’s medium, and studied with phase contrast and DIC microscopy. We have examined 1524 slides from 60 samples as of July 2003. Prior to our work, only three species of tardigrades had been previously reported from a few samples in the park. We have now recorded 42 species, 8 of which we believe may be new to science. Species richness estimates were calculated using EstimateS 6 software for each of the major tardigrade habitats. Overall, we predict that there are 47 to 76 species in the GSMNP, with generally similar species richness in soil, lichen, moss, and stream habitats. Species richness estimates were also used to determine that the number of tardigrade species was greater in mosses at breast height on trees than in mosses at the base of trees. [ABSTRACT FROM AUTHOR]

In the present study a character data set suitable for cladistic analysis at the family level was developed. A data matrix consisting of 50 morphological characters from 15 families of tardigrades was analyzed by maximum parsimony. Kinorhynchs, loriciferans, and gastrotrichs were used as outgroups. The results agree with the currently accepted hypothesis that Eutardigrada and Heterotardigrada are distinct monophyletic groups. Among the eutardigrades, Eohypsibiidae was found to be a sister group to Macrobiotidae+Hypsibiidae, while Milnesiidae was the basal eutardigrade family. The basal heterotardigrade family was found to be Oreellidae. Echiniscoideans grouped with some traditional Arthrotardigrada (Renaudarctidae, Coronarctidae+Batillipedidae) suggesting that the arthrotardigrades are not monophyletic. The 18S rRNA gene sequence of Batillipes mirus Richters, 1909 and Calohypsibius schusteri Nelson & McGlothlin, 1996 were obtained and their addition to a previously published dataset supports the monophyly of Heterotardigrada and of Parachela versus Apochela within the Eutardigrada. [ABSTRACT FROM AUTHOR]

Describes the feeding of young whale sharks on a copepod bloom near the Bay of La Paz, Mexico. Head movements of the sharks during feeding; Feeding behavior of the sharks.