Octopus DNA may reveal when the West Antarctic ice sheet most recently collapsed | CNN

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A study of octopus DNA may have solved an enduring mystery of when the rapidly melting West Antarctic ice sheet finally collapsed, unlocking important information about how many are to come. Sea levels may rise in a warm climate.

New research focuses on the genetic history of the Turquets octopus (Pareledone turqueti), which lives on the sea floor across the Antarctic, and what it can reveal about the region’s geology over time.

Tracing the species’ past encounters with different populations suggests that the most recent collapse of the ice sheet occurred more than 100,000 years ago during the period known as the Last Interglacial. something that geoscientists have suspected but not confirmed completely, according to the study published Thursdayin the journal Science.

This project is exciting because it offers a new perspective to solve a long-standing question in the geoscience community, said lead study author Sally Lau, a postdoctoral research fellow at James Cook University in Australia.

The DNA of living animals today contains all the information about their (past) ancestors, so it’s like a time capsule, he said.

The research team reached its findings by sequencing the DNA of 96 Turquets octopuses collected in institutions around the world and by fishing bycatch over the years. The oldest samples are dated to the 1990s, but when sequenced, their genes provide what appears to be a detailed family tree going back millions of years.

DNA analysis has enabled researchers to understand whether different populations of Turquets octopuses interbreed and at what point the interbreeding occurred.

It’s like doing a 23andMe on the octopus, Lau said, referring to the genetic testing company. This information is passed from parents to children and grandchildren and so on.

Today, populations of Turquets octopus in the Weddell, Amundsen and Ross seas are separated by the continent-sized West Antarctic ice shelves and do not mix.

However, the study suggests that there was a final genetic connection between these populations about 125,000 years ago, during the Last Interglacial, when global temperatures were similar to today.

This finding shows that the West Antarctic ice sheet collapsed during this time, an event that flooded coastal regions but opened up areas bound by ice on the sea floor for octopuses, which could eventually encounter and breed members of the Turquets population that were once geographically separated from each other.

What makes the WAIS important is that it is also Antarcticas current largest contributor to global sea level rise. A complete collapse could raise global sea levels by somewhere between 3 and 5 meters, said study author Jan Strugnell, professor and director of the Center for Sustainable Tropical Fisheries and Aquaculture at James Cook University. , in a statement. Strugnell first came up with the idea of ​​using genomic methods to determine if the ice sheet collapsed during the Last Interglacial.

Understanding how the WAIS was configured in the recent past when global temperatures were similar to today will help us better predict future sea level rise, he said.

Sally Lau (right), a postdoctoral research fellow at James Cook University in Australia, and Jan Strugnell, professor and director of the Center for Sustainable Tropical Fisheries and Aquaculture at James Cook University, led the research.

The team chose this type of octopus for the study because the animals are relatively immobile in that they can only crawl along the sea floor, meaning they are more likely to breed within their genetically distinct local populations. In contrast, a fast-moving marine species like krill has more homogenous DNA, distorting historical genetic connections, Lau said.

In addition, the biology of the Turquets octopus has been studied quite a bit, and scientists understand the DNA mutation rate and generation time, which are important for accurate molecular dating, Lau added.

Using octopus genomics is a new and exciting way to answer a key question about historical climate change, an expert says.

Previous studies involving crustacean and marine mollusk species have detected a biological signature of ice shelf collapse with a direct connection between the Ross and Weddell seas, Lau said. But the new Turquet octopus study is the first with high enough resolution data and a large enough sample size to understand whether that genetic connectivity is driven by ice sheet collapse or a slower movement of octopuses around their enclosures.

Lau said his team’s genetic approaches cannot reveal exactly when the ice sheet collapsed or how long the event took. However, with new octopus samples and more advanced DNA analysis techniques, these questions may be resolved in the future.

“We would like to continue to use DNA as a proxy to explore other parts of Antarctica whose climate history is poorly understood,” he said. Always looking for new species to test these scientific questions.

In a commentary published alongside the study, Andrea Dutton, a professor in the geoscience department at the University of Wisconsin-Madison, and Robert M.
DeConto, a professor at the School of Earth and Sustainability at the University of Massachusetts Amherst, calls the new research pioneering.

They noted that while geological evidence is mounting that the frozen expanse of the West Antarctic ice sheet may have collapsed during the Last Interglacial period, each study’s findings contained caves.

Bringing a whole different set of data to bear on this urgent issue raises some interesting questions, including whether this history will repeat itself, given the Earths current temperature trajectory, they added. .

Using octopus genomics is a new and exciting way to answer an important question about historical climate change, said Douglas Crawford, a professor of marine biology and ecology at the University of Miami. was not involved in the research.

It was a careful study with a sufficient sample size and a carefully analyzed set of genetic markers, he added.

It takes a challenging hypothesis and uses a completely independent data set that (finally) supports the WAIS collapse, he said via email.

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