In a surprising twist for marine science, researchers have discovered that copepods—tiny but crucial creatures at the base of the ocean food chain—use not one but two molecular toolkits to survive in a warming, acidifying ocean.
The discovery reveals a two-pronged strategy: one genetic, the other epigenetic, that helps these animals rapidly adjust and evolve across generations.
The findings, published July 15 in Proceedings of the National Academy of Sciences, offer a rare dose of optimism in climate research. Led by Melissa Pespeni at the University of Vermont, the study tracked 25 generations of marine copepods under simulated future ocean conditions. The result? Clear evidence that these organisms are not just adapting genetically over time, but also deploying rapid, reversible changes through epigenetic modifications—chemical tags on DNA that influence which genes get expressed.
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The team raised populations of Acartia tonsa—a globally abundant copepod species—in lab conditions mimicking ocean warming, acidification, and their combination. Over one year and 25 generations, researchers measured everything from egg production to genome-level changes. Using cutting-edge sequencing, they tracked:
- Genetic adaptation (DNA sequence changes)
- Epigenetic variation (DNA methylation)
- Gene expression patterns (which genes were turned on or off)
What they found was startling: genetic and epigenetic changes occurred in different regions of the genome and seemed to operate independently. Yet both mechanisms contributed to the copepods’ ability to tolerate stressful environments.
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In regions of the genome with high epigenetic change, the team found two to two-and-a-half times lower genetic change, suggesting the two modes of adaptation may avoid overlap. But both mattered. Epigenetic changes were most common in genes tied to stress response and the regulation of transposable elements—so-called “jumping genes” that can reshuffle the genome in times of stress.
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The new findings suggest that even when genetic diversity is low or evolutionary pressures mount quickly, epigenetic mechanisms might offer a critical buffer—buying time for long-term adaptation to catch up.
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The copepods were subjected to four conditions: ambient, acidified, warmed, and combined warming and acidification. Each condition had four replicate populations, and each replicate contained thousands of individuals. After 25 generations, whole-genome bisulfite sequencing and RNA sequencing revealed:
- 753 methylation sites significantly changed in the combined stress condition
- Negative correlation between epigenetic and genetic divergence
- Higher genetic diversity in genome regions with epigenetic changes
- Weak but significant correlation between methylation and gene expression
The combined effects suggest that epigenetics may allow populations to persist during stress, buying time for slower genetic changes to take root—a modern take on the classic “Baldwin Effect.”
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Journal: Proceedings of the National Academy of Sciences
Article Title: Complementary genetic and epigenetic changes facilitate rapid adaptation to multiple global change stressors
Publication Date: July 15, 2025
ScienceBlog.com, 24 July 2024. Full article.
