Extreme stress tolerance in tardigrades: surviving space conditions in low earth orbit

Journal of Zoological Systematics and Evolutionary Research (Impact Factor: 1.91). 05/2011; 49(special issue):90-97. DOI: 10.1111/j.1439-0469.2010.00605.x

ABSTRACT Most terrestrial tardigrade species possess the ability to enter a reversible ametabolic state termed anhydrobiosis in response to desiccation. In the anhydrobiotic state, tardigrades display an incredible capacity to tolerate extreme environmental stress, not necessarily encountered in their natural habitat. In this study, we determine the effect of different extreme stresses on initial survival, long-term survival and fecundity of selected species of limno-terrestrial tardigrades. The primary focus was to assess the effect of cosmic radiation. This was achieved through the RoTaRad (Rotifers, Tardigrades and Radiation) project on the BIOPAN 6 mission, funded by Agenzia Spaziale Italiana under the European Space Agency. To test their tolerance of space environment, tardigrades were sent into low earth orbit, and exposed to cosmic radiation and a microgravity environment. Experiments on Whatman-3 filters show an effect of cosmic radiation on the survival of the eutardigrade Richtersius coronifer just after returning to Earth; however, after 2 years of desiccation on Whatman-3 filters, none of the tardigrades previously exposed to cosmic radiation could be revived. In a microcosmos experiment, the tardigrades R. coronifer, Ramazzottius oberhauseri and Echiniscus testudo were desiccated on a moss substrate together with rotifers and nematodes. Very low survival rates were observed in this experiment, likely due to the applied desiccation protocol. Embryos of the tardigrade Milnesium tardigradum were also exposed to cosmic radiation; they all hatched in the laboratory after the flight. In addition, experiments testing extreme cold and vacuum tolerance in R. coronifer show that tardigrades in anhydrobiosis are unaffected by these conditions.

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    01/2015; 2015:1-7. DOI:10.1155/2015/167642
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    ABSTRACT: The position of Tardigrada in the animal tree of life is a subject that has received much attention, but still remains controversial. Whereas some think tardigrades should be categorized as cycloneuralians, most authors argue in favor of a phylogenetic position within Panarthropoda as a sister group to Arthropoda or Arthropoda + Onychophora. Thus far, neither molecular nor morphological investigations have provided conclusive results as to the tardigrade sister group relationships. In this article, we present a detailed description of the nervous system of the eutardigrade Halobiotus crispae, using immunostainings, confocal laser scanning microscopy, and computer‐aided three‐dimensional reconstructions supported by transmission electron microscopy. We report details regarding the structure of the brain as well as the ganglia of the ventral nerve cord. In contrast to the newest investigation, we find transverse commissures in the ventral ganglia, and our data suggest that the brain is partitioned into at least three lobes. Additionally, we can confirm the existence of a subpharyngeal ganglion previously called subesophagal ganglion. According to our results, the original suggestion of a brain comprised of at least three parts cannot be rejected, and the data presented supports a sister group relationship of Tardigrada to 1) Arthropoda or 2) Onychophora or 3) Arthropoda + Onychophora. J. Morphol. 2012. © 2012 Wiley Periodicals, Inc.
    Journal of Morphology 01/2012; 273(11). · 1.55 Impact Factor


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