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by Joshua Brown, University of Vermont<\/a><\/p>\n In a first-of-its-kind experiment tracing evolution across 25 generations, scientists have discovered that marine copepods\u2014the tiny crustaceans at the heart of the ocean food web\u2014rely on a largely unknown biological toolkit to survive the stresses of climate change.<\/p>\n Published July 15, 2025, in the Proceedings of the National Academy of Sciences, the study<\/a> reveals that it\u2019s not only genetic changes (permanent alterations to DNA) that help these animals adapt to warming and acidifying ocean conditions. In addition, little-known epigenetic changes (temporary \u201con\/off\u201d chemical modifications to parts of DNA) play a crucial role too. Remarkably, the researchers discovered that the two mechanisms operate independently but in concert, offering what they call a \u201ctwo-pronged strategy\u201d for long-term resilience.<\/p>\n \u201cThis is a story of molecular hope in the face of a rapidly changing planet,\u201d said senior author Melissa Pespeni<\/a>, associate professor of biology at the University of Vermont. \u201cWe found that evolution is not working from one toolbox, but two\u2014and they\u2019re complementary.\u201d\u00a0<\/p>\n Until now, few studies have tracked genetic and epigenetic changes in tandem over many generations. This experiment is one of the first to do so in a long-term, replicated evolution study\u2014offering some of the strongest evidence yet that epigenetic change can help populations survive and perhaps even allow future genetic adaptation.<\/p>\n Which means that copepods may be tougher under the stresses of a warming ocean than scientists previously would have predicted. And that could be good news for the many fish species who eat copepods as their primary prey\u2014and for the many other creatures, including humans, who eat fish.<\/p>\n Evolution in a Bucket<\/p>\n To conduct this study, Pespeni and colleagues at GEOMAR Helmholtz Centre for Ocean Research Kiel in Germany and at the University of Connecticut, raised populations of Acartia tonsa\u2014a foundational marine copepod species\u2014in carefully controlled laboratory buckets. Some buckets were warmed, others acidified, and some experienced both. Over a year, these fast-reproducing animals cycled through 25 generations.<\/p>\n The team measured their response not only at the organismal level\u2014how many eggs the copepods laid, their thermal tolerance, development rates, and survival\u2014but also at the molecular level. Using state-of-the-art sequencing, the researchers mapped changes in the animals\u2019 genome (genetic adaptation), epigenome (molecular markers that influence gene expression), and transcriptome (which genes were turned on and off).<\/p>\n They found striking and consistent epigenetic and genetic changes across the treatment groups\u2014but, surprisingly, these changes occurred in different regions of the genome.<\/p>\n \u201cThat\u2019s really powerful,\u201d said Pespeni. \u201cIt shows that the epigenetic variation was not just dragged along with the genetic variation. These are independent mechanisms that the organism is using to cope.\u201d<\/p>\n Evolution\u2019s Dynamic Duo<\/p>\n In genetics, variation provides the raw material for evolution. Populations with more genetic variation are generally better equipped to respond to environmental change. But what happens when genetic variation runs low\u2014or change happens too fast for slow-moving genetic mutations to keep up?<\/p>\n That\u2019s where epigenetics comes in.<\/p>\n \u201cEpigenetic changes can happen within an individual\u2019s lifetime and don\u2019t require a new mutation,\u201d said Pespeni. \u201cThey\u2019re reversible and fast.\u201d Exactly what a copepod wants when facing a heat wave or a spike in ocean acidification.<\/p>\n The study found that regions of the copepod genome with high epigenetic divergence\u2014like shifts in methylation\u2014had two to two-and-a-half times lower genetic divergence, suggesting that these mechanisms may inhibit each other or target different functions. But both types of changes mattered.<\/p>\n Epigenetic divergence was particularly concentrated in genes involved in stress responses and the regulation of transposable elements\u2014 bits of “jumping” DNA that can reshuffle the genome. And importantly, these epigenetic changes were correlated with changes in gene expression, directly shaping how the organism functions.<\/p>\n \u201cTogether, these results show that genetic and epigenetic variation are not redundant,\u201d Pespeni explained. \u201cThey are evolution\u2019s dynamic duo\u2014providing two independent toolkits for organisms facing rapid global change.\u201d<\/p>\n A Shift in Evolutionary Thinking<\/p>\n The findings have profound implications for how scientists understand evolution and resilience in the Anthropocene.<\/p>\n \u201cEpigenetics is not just a side note in biology,\u201d said Pespeni. \u201cIt\u2019s important. We\u2019re not rewriting Darwin, but we are expanding the Modern Synthesis to include this player.\u201d<\/p>\n \u201cThis might sound like neo-Lamarckian heresy,\u201d Pespeni said with a laugh, referencing the discredited idea that traits acquired during a lifetime can be passed to future generations. (Because you spent years in the garden and developed rough calloused hands doesn\u2019t mean your child will be born with \u201cgardener\u2019s hands\u201d or a love of lettuce.) \u201cBut what we\u2019re seeing is that molecular and physiological phenotypes\u2014like how an organism responds to temperature stress\u2014can be passed down to future generations through epigenetic means, at least temporarily.\u201d<\/p>\n Why Copepods Matter<\/p>\n Tiny as they are, Acartia tonsa and other copepods play a massive role in the ocean ecosystem and global carbon cycle. They\u2019re the base of the marine food web, sustaining fish, whales, and seabirds. They also help cycle nutrients and carbon in the ocean.<\/p>\n \u201cWithout copepods, you don\u2019t have fish, you don\u2019t have whales, you don\u2019t have the ocean system we know,\u201d said Pespeni. \u201cAnd they are arguably the most abundant animal on Earth.\u201d<\/p>\n The fact that copepods can survive and quickly adapt across generations\u2014say, during a short, intense heat wave\u2014could make a long-term difference in maintaining biodiversity and ecosystem function in a warming world.<\/p>\n \u201cAllowing an organism to survive a few extra generations during a stress event could preserve genetic diversity and buy time for longer-term adaptation,\u201d said Pespeni.\u00a0<\/p>\n Hope in the Genome<\/p>\n This research may offer new optimism to the grim tale of global changes. While genetic diversity has long been seen as the well of evolutionary potential, this study suggests that epigenetic diversity might offer a hidden reserve of strength\u2014one that can be tapped quickly, flexibly, and repeatedly. \u201cAnd that’s important,\u201d Pespeni says, \u201cbecause it shows these organisms may be more resilient than previously expected.\u201d<\/p>\n Source: July 24, 2025. University of Vermont<\/p>\n To support vital journalism, access our archives and get unique features like our award-winning profiles, Book of Lists & Business-to-Business Directory, subscribe HERE<\/a>!<\/p>\n![\"copepopds](\"https:\/\/www.uvm.edu\/d10-files\/styles\/default_1920\/public\/images\/2025-07\/20190417-copepods.wikimedia-image_0.jpeg?itok=p8OkFOhG\")
Copepods are tiny crustaceans, barely visible to the naked eye, but beautiful under a microscope and hugely important to life on Earth. They’re found in nearly every freshwater and marine habitat\u2014and they may be the most abundant animals in the ocean. (Photo: Andrei Savitsky)<\/p>\n