• Rapid evolution fuels transcriptional pl

    From ScienceDaily@1:317/3 to All on Thu Mar 3 21:30:42 2022
    Rapid evolution fuels transcriptional plasticity in fish species to cope
    with ocean acidification

    Date:
    March 3, 2022
    Source:
    The University of Hong Kong
    Summary:
    A research team has revealed the basis to variability across
    different fish species and uncovered that some species evolve
    more rapidly, providing them with evolved molecular toolkits and
    allowing them able to cope with future ocean acidification.



    FULL STORY ==========================================================================
    A research team led by Dr Celia Schunter at School of Biological
    Sciences (area of Ecology and Biodiversity) & The Swire Institute of
    Marine Science, The University of Hong Kong (HKU), in collaboration
    with researchers from The University of Adelaide, James Cook University
    in Australia, IRD Institute in New Caledonia, and Okinawa Institute of
    Science and Technology Graduate University in Japan, revealed the basis to variability across different fish species and uncovered that some species evolve more rapidly, providing them with evolved molecular toolkits and allowing them able to cope with future ocean acidification. The journal
    paper was recently published in Global Change Biology.


    ========================================================================== Global ocean surface pH is projected to decline with the ongoing
    uptake of anthropogenic atmospheric CO2 by the oceans, a process termed
    ocean acidification (OA). A decade of laboratory experiments indicate
    that predicted OA conditions affect some marine fishes' physiological performance, growth, survival, and crucial behaviours for the survival
    of the fish.

    To test how marine life will respond and whether adaptation to this
    rapid acidification is possible, researchers went to a remote place
    on this planet to study in situ exposure to elevated partial pressure
    of carbon dioxide (pCO2, the amount of carbon dioxide dissolved in
    water) and be able to predict how in the wild fish can cope with these environmental conditions predicted to exist across the globe by the
    end of this century. With rapidly changing environments due to human activities, it is crucial to be able to predict what will happen to
    marine organisms and in particular fish populations to optimise our conservation and management efforts.

    The study here indicated some fish species that evolve more rapidly may
    have a flexible way to cope with OA, which should be helpful for these
    species to maintain their population size and biodiversity. However,
    for some other species evolving slowly, OA will be difficult for them
    once the OA level is beyond their tolerance levels.

    Natural laboratories with elevated pCO2 Volcanic CO2 seeps can be used as natural laboratories where CO2 rises from the substratum and acidifies
    the surrounding seawater to levels similar to, or sometimes beyond, the projections for ocean acidification by the end of this century. Six adult
    coral reef fish species including damselfishes and a cardinalfish species
    from a reef within the Upa-Upasina CO2 seep in Papua New Guinea (pH 7.77,
    pCO2 846 myatm) and an adjacent reef (500 m distance) with ambient pCO2
    (pH 8.01, pCO2 443 myatm) were sampled, tissues were extracted, analysed
    and sequenced for their cellular response to elevated CO2 in their
    brains. The six fish species in this study are common coral reef fish but exhibit slightly different ecologies including differences in parental
    care and being active during the day or night, and therefore we can,
    to a certain extent, extrapolate the found patterns also to other fishes.



    ========================================================================== Common responses to OA across species Elevated pCO2 induced common
    molecular responses related to circadian rhythm as well as the immune
    system several of the species, revealing that these are important
    processes that are affected by elevated CO2 for many species.

    Circadian rhythms are the drivers of our 24-h biological clocks and exist
    in human, other animals and plants. They drive our sleep patterns and
    also our metabolism, and this shows that the circadian rhythm core genes
    affect many other downstream functions and can also affect behaviour. The adjustment here of the Circadian genes with elevated CO2 seemed to drive
    gene expression changes of other genes in the brain, which may allow
    the fish to flexibly react to the CO2.

    Immune regulation appears to further be an important function involved
    in the response to elevated pCO2. Interestingly, while this was the case
    across numerous species of reef fish, the nocturnal species exhibited an elevation in immune genes, whereas other species supressed the immune
    genes with elevated CO2. This is a phenomenon not previously studies
    and hint to the fact that nocturnal and diurnal species may respond
    differently and this warrant further study.

    A fish species possessing evolved molecular toolkits to cope with future
    OA The spiny damselfish, A. polyacanthus, can regulate the pH levels
    within its cells through the gene expression changes to respond the environmental elevated pCO2 at the CO2 seep. We originally thought that an elevation in the pCO2 to end-of-century predictions would not be a large
    impact to fishes, as they know how to regulate the pH, however we see
    that these coral fish species induced significant expression changes in
    many genes, especially A. polyacanthus, hence showing the need to regulate
    the cells in the brain in response to the CO2 levels in the ocean waters.



    ==========================================================================
    For a brain to function properly and signalling to occur in the brain, providing the different neurons with essential information, ions such as calcium, sodium, potassium and chloride need to be transported. Here we
    found that such transporter genes changed their expression, especially
    for A.

    polyacanthus when living in the seeps, which shows that neural
    signal transductions needs to be altered in response to elevated
    CO2. Interestingly, during our sample collection at the remote reef
    a storm arose for 24 hours, which moved a lot of water of the CO2 seep
    site and increased the pH temporarily. We were able to collect some spiny damselfish during this time and now see that all the cellular changes
    are reversible as they changed quickly back to the levels of what we see
    at the control reef with current day CO2 levels. These results indicated
    A. polyacanthus may be able to switch their gene expression to respond
    rapidly changing pH levels.

    The spiny damselfish species, A. polyacanthus, evolve more rapidly than
    the other species over the past 15 million years, which leaves this
    species with an enhanced potential to adapt to changing environmental conditions. In particular, the genes seen to be important in the response
    to living in elevated pCO2, such as genes involved in intracellular
    pH regulation, circadian rhythm (can adjust the expression of many
    other genes), and ion transport (have impact on the neural signal transduction), also indicated an increased evolutionary rate. This can
    lead to increased gene expression alteration accordingly to environmental change namely transcriptional plasticity -- to ocean acidification in
    A. polyacanthus. As such, this species may possess evolved molecular
    toolkits to cope with future ocean acidification.

    "It has been quite puzzling why some species struggle more than others
    with ocean acidification conditions. Our expedition to this remote CO2
    vent site allowed us to look at many fish species that live naturally
    in these elevated CO2 conditions and complete parts of the puzzle,"
    Dr Celia Schunter remarked, "we see that possibly limited by slow
    evolution, some fish species may not be flexible when responding to
    elevated CO2 conditions and struggle more." "Species that evolve more
    rapidly may have a flexible way to cope with ocean acidification, which
    should be helpful for these species to maintain their population size
    and biodiversity. However, for some other species evolving more slowly,
    ocean acidification will be difficult for them once the pH level beyond
    their abilities to maintain their acid-base balance. Previously we did
    not understand why some species struggled and others didn't as much and understanding why some may be 'winners' or 'losers' is important so we
    can protect especially the ones that will not be able to cope and to
    keep the balance in the ecosystem," added Dr Schunter.

    This study uncovered that some wild fish species may be equipped with
    inherent molecular tools via rapid evolution to cope with elevated
    pCO2 predicted to occur by the end of this century. The next goal for
    the research team is to validate if other ecosystems exhibit the same
    findings. Meanwhile, ocean acidification still is a threat for the fish
    species evolving slowly once the level of ocean acidification rises
    beyond their regulation ability. As such, slowing the decreasing global
    pH is key to maintaining high biodiversity of fish.

    ========================================================================== Story Source: Materials provided by The_University_of_Hong_Kong. Note:
    Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Jingliang Kang, Ivan Nagelkerken, Jodie L. Rummer, Riccardo
    Rodolfo‐Metalpa, Philip L. Munday, Timothy Ravasi, Celia
    Schunter.

    Rapid evolution fuels transcriptional plasticity to ocean
    acidification.

    Global Change Biology, 2022; DOI: 10.1111/gcb.16119 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/03/220303141224.htm

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