The African turquoise killifish, resident to semi-dry terrains, has evolved a unique survival technique to get through the extensive dry periods that deplete its natural habitats annually.
Embryos of this minuscule fish, measuring merely the length of a thumb, cease development shortly after their brains and hearts have started to form. They remain in a dormant state called ‘diapause’ for several months, effectively waiting out the drought.
Researchers from the United States and Germany have now uncovered how the African turquoise killifish (Nothobranchius furzeri) accomplishes this feat: by activating ancient genes within their DNA that date back over 473 million years.
This revelation is quite unexpected since N. furzeri only recently, about 18 million years ago, acquired the ability to enter diapause after colonizing temporary ponds.
The scientists’ gene analysis during diapause revealed that the killifish are using very old evolutionary tools to perform this relatively new adaptation.
“Even though diapause evolved relatively recently, the genes that are specialized in diapause are really ancient,” explains Stanford University molecular biologist Anne Brunet.
Paralogs are pairs of genes that arise when a gene is duplicated either within the same chromosome or onto another one. This duplication, along with random mutations, is a recognized method for gene evolution and acquiring novel functions.
It was discovered that in the turquoise killifish, one gene from each paralog pair had increased activity during diapause, while the other was active during regular development.
“The whole program is like day and night,” Brunet states.
When the researchers compared African turquoise killifish to other species of killifish, some of which do not undergo diapause, they noted that N. furzeri had ‘unlocked’ numerous ancient paralogs specifically for use in diapause.
It’s likely that through genomic adjustments, the N. furzeri killifish made these paralog genes more accessible for protein synthesis, assisting adaptation to the harsh conditions of its environment.
During diapause, a metabolic change occurs that leads to the production of abundant very-long-chain fatty acids, which are believed to help protect the killifish’s DNA from damage.
While not as drought-hardy as tardigrades, the African turquoise killifish’s ability to suspend its development without detriment to its emerging organs is nonetheless impressive.
“Killifish are the only vertebrate species that we know of that can undergo diapause so late in development,” comments study lead Param Priya Singh, a bioinformatician at the University of California, San Francisco.
Surprisingly, this extreme halt in development during a normally crucial growth phase does not seem to affect the lifespan of a fully grown killifish.
Singh and his collaborators suggest their findings on the African turquoise killifish’s lipid-rich dormant state could lead to new strategies for tissue preservation and combating age-related diseases.
The full study can be found in the journal Cell.
FAQ Section
What is the African turquoise killifish?
The African turquoise killifish is a small fish from semi-arid regions that has evolved a survival strategy to endure long droughts by entering a state of arrested development known as diapause.
How long have the genes used in diapause been a part of the killifish’s genome?
The genes specialized for diapause in the killifish are ancient, dating back over 473 million years, even though the ability to enter diapause evolved around 18 million years ago.
What are paralogs?
Paralogs are pairs of genes that arise from a duplication event in which a gene is copied either within the same chromosome or onto another one, which can lead to new gene functions.
How do the findings of this study impact our understanding of longevity and tissue preservation?
The study suggests that the lipid-based survival mechanism of the African turquoise killifish could open up possibilities for strategies in long-term tissue preservation and potential treatments for age-related diseases.
Where can I read the full study?
The complete study is published in the scientific journal Cell and can be accessed here.