K. Ingemar Jönsson

Tardigrades survive exposure to space in low Earth orbit

Summary Vacuum (imposing extreme dehydration) and solar/galactic cosmic radiation prevent survival of most organisms in space [1]. Only anhydrobiotic organisms, which have evolved adaptations to survive more or less complete desiccation, have a potential to survive space vacuum, and few organisms can stand the unfiltered solar radiation in space. Tardigrades, commonly known as water-bears, are among the most desiccation and radiation-tolerant animals and have been shown to survive extreme levels of ionizing radiation [2–4]. Here, we show that tardigrades are also able to survive space vacuum without loss in survival, and that some specimens even recovered after combined exposure to space vacuum and solar radiation. These results add the first animal to the exclusive and short list of organisms that have survived such exposure.

Radiation tolerance in the eutardigrade Richtersius coronifer

Purpose: Tardigrades have a reputation of being extremely tolerant to extreme environmental conditions including tolerance to ionizing radiation while in a desiccated, anhydrobiotic state. However, the evidence for radio-tolerance in tardigrades is based on only one previous report, and there is an obvious need for complementary studies. In this paper we report an investigation on radio-tolerance in desiccated and hydrated specimens of the eutardigrade Richtersius coronifer. Materials and methods: Groups of 30 – 50 tardigrades were exposed to γ-radiation at doses between 1.0 – 9.0 (anhydrobiotic animals) or 0.5 – 5.0 (hydrated animals) kGy and the animals were followed until all were dead. Radiation tolerance of both desiccated and hydrated tardigrades was studied. Results: Both desiccated and hydrated animals irradiated with 0.5 and 1 kGy did not deviate in survival from the control groups. Animals from all exposed groups underwent their moulting and egg production cycle, but at decreasing frequency for doses above 1 kGy. No eggs laid by irradiated animals hatched, while eggs laid by controls did so. Conclusion: Our study suggests that radiation tolerance in tardigrades is not due to biochemical protectants connected with the desiccated state. Rather, cryptobiotic tardigrades may rely on efficient mechanisms of DNA repair, the nature of which is currently unknown.

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. (Less)

Solving problems in social–ecological systems : definition, practice and barriers of transdisciplinary research

Translating policies about sustainable development as a social process and sustainability outcomes into the real world of social–ecological systems involves several challenges. Hence, research policies advocate improved innovative problem-solving capacity. One approach is transdisciplinary research that integrates research disciplines, as well as researchers and practitioners. Drawing upon 14 experiences of problem-solving, we used group modeling to map perceived barriers and bridges for researchers’ and practitioners’ joint knowledge production and learning towards transdisciplinary research. The analysis indicated that the transdisciplinary research process is influenced by (1) the amount of traditional disciplinary formal and informal control, (2) adaptation of project applications to fill the transdisciplinary research agenda, (3) stakeholder participation, and (4) functional team building/development based on self-reflection and experienced leadership. Focusing on implementation of green infrastructure policy as a common denominator for the delivery of ecosystem services and human well-being, we discuss how to diagnose social–ecological systems, and use knowledge production and collaborative learning as treatments.

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.

Anhydrobiotic survival in populations of the tardigrades Richtersius coronifer and Ramazzottius oberhaeuseri from Italy and Sweden

We report a study on anhydrobiotic survival in the eutardigrades Richtersius coronifer and Ramazzottius oberhaeuseri. In each of these species, we investigated the anhydrobiotic survival of two populations, one from Sweden and one from Italy. We found that anhydrobiotic survival was similar in the Swedish and the Italian populations in both species, indicating no divergence with respect to anhydrobiotic capacity. Body size had a strong effect on the probability to recover from anhydrobiosis, but the effect was in opposite direction in the two tardigrade species. Ramazzottius oberhaeuseri had a considerable higher overall survival (66%) than R. coronifer (40%). This result is in line with earlier studies that found R. oberhaeuseri to have a very high water-retentive capacity.

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

BackgroundThe 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 vs. environmental components into the level of melanism expressed. We investigated variation in the degree of melanism in the common frog (Rana temporaria; 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.ResultsWe 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 (PST ) and neutral marker loci (FST ) revealed that the PST > FST , 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.ConclusionsAs 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.

Causes and Consequences of Excess Resistance in Cryptobiotic Metazoans

Despite more than 200 yr of recognition that some microscopic metazoans survive environmental conditions far beyond those experienced in nature while in a cryptobiotic state, this phenomenon has received little attention from evolutionary biologists. The excess environmental resistance exhibited by cryptobiotic organisms cannot be viewed as an adaptation within current evolutionary biology. Rather, excess resistance may have evolved as a by‐product of natural selection for tolerance to desiccation or other naturally occurring environmental agents. The combined effects of desiccation, metabolic arrest, effective stabilization of dry or frozen cells by protectant molecules, and efficient DNA repair mechanisms may have led to a protection of the organism against conditions far beyond those experienced in nature.

Does testis weight decline towards the Subarctic? A case study on the common frog, Rana temporaria

Interpopulation comparisons of variation in resource availability and in allocation patterns along altitudinal and latitudinal gradients allow insights into the mechanisms shaping the life history of animals. Patterns of between-population differences in female life history traits have been studied intensively across a wide range of taxa, but similar investigations in males have remained scarce. To study if testis weight—a measure of reproductive investment—varies on a geographical scale in anurans, we focussed on the variation in relative testis weight (RelTW) and asymmetry in 22 populations of the common frog Rana temporaria along a 1,600-km latitudinal transect across the Scandinavian peninsula. We found that RelTW decreased towards the north. Body mass and body length both had independent positive effects on testes mass. We found evidence for directional asymmetry (DA) in testis weight with the right testis being larger than the left. The level of DA in testis weight was not related to latitude, but both body mass and testes mass had independent positive effects on asymmetry. We discuss the northwards decrease in RelTW in terms of a decreased reproductive investment as a possible consequence of harsher environmental conditions, and perhaps also, weaker sexual selection in the north than in the south.

Reproductive effort tactics : balancing pre- and postbreeding costs of reproduction

Costs of reproduction are most frequently evaluated in terms of postbreeding survival and fecundity costs. Such demographic costs are expected to follow as the female drains her somatic resources into reproduction. However, some reproductive tactics may lead to costs of reproduction that are expressed in terms of prebreeding survival. We propose an optimality model where total absolute effort may originate from two different components. The first component measures the amount of resources that the female accumulates for reproduction during the prebreeding period. The second component represents the amount of resources drained from somatic demands relative to non-reproductive individuals. While our model allows both components to imply pre-and postbreeding survival costs, we mainly focus on the case where accumulation effort implies costs on prebreeding survival and somatic effort implies costs on postbreeding survival. Effective fecundity is assumed to be a function of both components. We consider accumulation and somatic effort as alternative options of an organisms reproductive effort tactic, and solve for optimal tactics by maximizing fitness over a single breeding season, assuming a constant total investment in reproduction. The present analysis suggests that the evolution of accumulation effort requires that marginal prebreeding costs due to accumulated resources remain low relative to marginal postbreeding costs implied by somatic effort. When the total investment in reproduction increases, optimal somatic effort increases relative to optimal accumulation effort. Our analysis demonstrates that natural selection may well favour different effort tactics satisfying the energy demands of reproduction, some of which may involve optimization of the balance between pre- and postbreeding costs of reproduction. For organisms relying on tactics implying prebreeding costs, empirical studies monitoring postbreeding survival only may not reveal the major costs of reproduction.