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

Disability Insurance, Population Health and Employment in Sweden

This paper describes the development of population health and disability insurance utilization for older workers in Sweden and analyses the relation between the two. We use three different measures of population health: (1) the mortality rate (measured between 1950 and 2009); (2) the prevalence of different types of health deficiencies obtained from Statistics Sweden’s Survey on Living Conditions (ULF, 1975-2005); (3) the utilization of health care from the inpatient register (1968–2008). We also study the development of the relative health between disability insurance recipients and non-recipients. Finally, we study the effect of the introduction of less strict eligibility criteria for older workers in 1970 and 1972 as well as the subsequent abolishment of these rules in 1991 and 1997, respectively.Disability insurance; Population health

Facts and fiction about long-term survival in tardigrades

Tardigrades have achieved a widespread reputation for an ability to survive more than a century in an inactive, ametabolic state called cryptobiosis, However, a closer look at the empirical evidence provides little support for the claim that tardigrades are capable of century-long survival. Instead, current evidence suggests that a decade may more realistically represent the upper limit of cryptobiotic survival in the most resistant tardigrades

Long-term anhydrobiotic survival in semi-terrestrial micrometazoans

This study represents the first systematic investigation of long-term anhydrobiotic survival in tardigrades, rotifers and nematodes inhabiting mosses and lichens. Sixty-three different samples from public and private collections, kept dry for 9-138 years, were examined. Rotifers of the genus Mniohia and the eutardigrade Ramazzottius oberhaeuseri (hatched from eggs) were found alive from one of the samples (9 years old). These observations represent the longest record for rotifers in the anhydrobiotic state. For tardigrades, our results confirm previous reports on the upper limit of anhydrobiotic survival under atmospheric oxygen conditions. This study suggests the possibility that tardigrade eggs are able to withstand longer periods in anhydrobiosis than animals. Some problems related to the evaluation of long-term anhydrobiotic survival, such as contamination and chemical treatments of samples, are reported. The possible role of the microenvironment in which the anhydrobiotic animals are kept is discussed

An experimental study on tolerance to hypoxia in tardigrades

Introduction: Tardigrades are small aquatic invertebrates with well documented tolerance to several environmental stresses, including desiccation, low temperature, and radiation, and an ability to survive long periods in a cryptobiotic state under arrested metabolism. Many tardigrade populations live in habitats where temporary exposure to hypoxia is expected, e.g., benthic layers or substrates that regularly undergo desiccation, but tolerance to hypoxia has so far not been thoroughly investigated in tardigrades.Method: We studied the response to exposure for hypoxia (<1 ppm) during 1–24 h in two tardigrade species, Richtersius cf. coronifer and Hypsibius exemplaris. The animals were exposed to hypoxia in their hydrated active state.Results: Survival was high in both species after the shortest exposures to hypoxia but tended to decline with longer exposures, with almost complete failure to recover after 24 h in hypoxia. R. cf. coronifer tended to be more tolerant than H. exemplaris. When oxygen level was gradually reduced from 8 to 1 ppm, behavioral responses in terms of irregular body movements were first observed at 3–4 ppm.Discussion: The study shows that both limno-terrestrial and freshwater tardigrades are able to recover after exposure to severe hypoxia, but only exposure for relatively short periods of time. It also indicates that tardigrade species have different sensitivity and response patterns to exposure to hypoxia. These results will hopefully encourage more studies on how tardigrades are affected by and respond to hypoxic conditions

A comparative ultrastructure study of storage cells in the eutardigrade Richtersius coronifer in the hydrated state and after desiccation and heating stress

Tardigrades represent an invertebrate phylum with no circulatory or respiratory system. Their body cavity is filled with free storage cells of the coelomocyte-type, which are responsible for important physiological functions. We report a study comparing the ultrastructure of storage cells in anhydrobiotic and hydrated specimens of the eutardigrade Richtersius coronifer. We also analysed the effect of temperature stress on storage cell structure. Firstly, we verified two types of ultrastructurally different storage cells, which differ in cellular organelle complexity, amount and content of reserve material and connection to oogenetic stage. Type I cells were found to differ ultrastructurally depending on the oogenetic stage of the animal. The main function of these cells is energy storage. Storage cells of Type I were also observed in the single male that was found among the analysed specimens. The second cell type, Type II, found only in females, represents young undifferentiated cells, possibly stem cells. The two types of cells also differ with respect to the presence of nucleolar vacuoles, which are related to oogenetic stages and to changes in nucleolic activity during oogenesis. Secondly, this study revealed that storage cells are not ultrastructurally affected by six months of desiccation or by heating following this desiccation period. However, heating of the desiccated animals (tuns) tended to reduce animal survival, indicating that long-term desiccation makes these animals more vulnerable to heat stress. We confirmed the degradative pathways during the rehydration process after desiccation and heat stress. Our study is the first to document two ultrastructurally different types of storage cells in tardigrades and reveals new perspectives for further studies of tardigrade storage cells

Morphological and molecular analyses on Richtersius (Eutardigrada) diversity reveal its new systematic position and lead to the establishment of a new genus and a new family within Macrobiotoidea

Important contributions have been made to the systematics of Eutardigrada in recent years, but these have also revealed that several taxa are polyphyletic and that cryptic species are present. To shed light on the taxonomy and systematic position of the genus Richtersius (Eutardigrada, Macrobiotoidea), six populations attributed to Richtersius coronifer were collected and analysed from morphological (light and scanning electron microscopy) and molecular (mitochondrial cytochrome oxidase subunit 1, 18S, 28S) points of view. In particular, a new morphometric index (claw common tract: length of the common tract of the claw/total claw length 9 100) and a new morphological character (stalk system) were introduced. Our integrative study was able to unveil the ‘cryptic’ species diversity within Richtersius, showing that the genus contains more than one evolutionary lineage. A morphological peculiarity in the animals of all lineages is the dimorphism in the morphology of the cuticle. Cuticular pores are present in the newborns and are lost with the first moult; this morphological change represents a novelty in the life cycle of eutardigrades. The phylogenetic analyses carried out on Richtersius populations and other Macrobiotoidea show that Richtersius is closely related to Macrobiotus islandicus, whereas Adorybiotus granulatus is more related to Richtersius and M. islandicus than to other members of the genus Macrobiotus (type genus of Macrobiotidae); therefore, the genus Macrobiotus and the family Macrobiotidae are not monophyletic. Based on these results, the new genus Diaforobiotus (for M. islandicus) and the new family Richtersiidae (composed of Richtersius, Diaforobiotus gen. nov., and Adorybiotus) are established

Increasing melanism along a latitudinal gradient in a widespread amphibian: local adaptation, ontogenic or environmental plasticity?

<p>Abstract</p> <p>Background</p> <p>The thermal benefits of melanism in ectothermic animals are widely recognized, but relatively little is known about population differentiation in the degree of melanism along thermal gradients, and the relative contributions of genetic <it>vs. </it>environmental components into the level of melanism expressed. We investigated variation in the degree of melanism in the common frog (<it>Rana temporaria</it>; an active heliotherm thermoregulator) by comparing the degree of melanism (i) among twelve populations spanning over 1500 km long latitudinal gradient across the Scandinavian Peninsula and (ii) between two populations from latitudinal extremes subjected to larval temperature treatments in a common garden experiment.</p> <p>Results</p> <p>We found that the degree of melanism increased steeply in the wild as a function of latitude. Comparison of the degree of population differentiation in melanism (<it>P_ST</it>) and neutral marker loci (<it>F_ST</it>) revealed that the <it>P_ST</it> ><it>F_ST</it>, indicating that the differences cannot be explained by random genetic drift alone. However, the latitudinal trend observed in the wild was not present in the common garden data, suggesting that the cline in nature is not attributable to direct genetic differences.</p> <p>Conclusions</p> <p>As straightforward local adaptation can be ruled out, the observed trend is likely to result from environment-driven phenotypic plasticity or ontogenetic plasticity coupled with population differences in age structure. In general, our results provide an example how phenotypic plasticity or even plain ontogeny can drive latitudinal clines and result in patterns perfectly matching the genetic differences expected under adaptive hypotheses.</p

Phobos LIFE (Living Interplanetary Flight Experiment)

The Planetary Society's Phobos Living Interplanetary Flight Experiment (Phobos LIFE) flew in the sample return capsule of the Russian Federal Space Agency's Phobos Grunt mission and was to have been a test of one aspect of the hypothesis that life can move between nearby planets within ejected rocks. Although the Phobos Grunt mission failed, we present here the scientific and engineering design and motivation of the Phobos LIFE experiment to assist with the scientific and engineering design of similar future experiments. Phobos LIFE flew selected organisms in a simulated meteoroid. The 34-month voyage would have been the first such test to occur in the high-radiation environment outside the protection of Earth's magnetosphere for more than a few days. The patented Phobos LIFE “biomodule” is an 88 g cylinder consisting of a titanium outer shell, several types of redundant seals, and 31 individual Delrin sample containers. Phobos LIFE contained 10 different organisms, representing all three domains of life, and one soil sample. The organisms are all very well characterized, most with sequenced genomes. Most are extremophiles, and most have flown in low Earth orbit. Upon return from space, the health and characteristics of organisms were to have been compared with controls that remained on Earth and have not yet been opened