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
--- up 3 days, 10 hours, 50 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)