Survival in extreme environments - on current knowledge of adaptations in tardigrades

Nadia Møbjerg, Kenneth Halberg, Aslak Jørgensen, Dennis Persson, Morten Bjørn, Hans Ramløv, R.M. Kristensen

    Research output: Contribution to journalReviewpeer-review

    Abstract

    Tardigrades are microscopic animals found worldwide in aquatic as well as
    terrestrial ecosystems. They belong to the invertebrate superclade Ecdysozoa,
    as do the two major invertebrate model organisms: Caenorhabditis elegans
    and Drosophila melanogaster. We present a brief description of the tardigrades
    and highlight species that are currently used as models for physiological
    and molecular investigations. Tardigrades are uniquely adapted to a
    range of environmental extremes. Cryptobiosis, currently referred to as a
    reversible ametabolic state induced by e.g. desiccation, is common especially
    among limno-terrestrial species. It has been shown that the entry and exit of
    cryptobiosis may involve synthesis of bioprotectants in the form of selective
    carbohydrates and proteins as well as high levels of antioxidant enzymes and
    other free radical scavengers. However, at present a general scheme of
    mechanisms explaining this phenomenon is lacking. Importantly, recent
    research has shown that tardigrades even in their active states may be extremely
    tolerant to environmental stress, handling extreme levels of ionizing
    radiation, large fluctuation in external salinity and avoiding freezing by
    supercooling to below )20 C, presumably relying on efficient DNA repair
    mechanisms and osmoregulation. This review summarizes the current
    knowledge on adaptations found among tardigrades, and presents new data
    on tardigrade cell numbers and osmoregulation.
    Original languageEnglish
    JournalActa Physiologica (Print)
    Volume202
    Issue number3
    Pages (from-to)409-420
    Number of pages12
    ISSN1748-1708
    DOIs
    Publication statusPublished - 2011

    Keywords

    • cell numbers
    • cryptobiosis
    • evolution
    • osmoreglation
    • supercooling
    • tardigrade

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