by Subscribe to CNN’s Wonder Theory science newsletter. Explore the universe with news about fascinating discoveries, scientific breakthroughs and more.
A study of octopus DNA may have solved a persistent mystery about when the rapidly melting West Antarctic Ice Sheet last collapsed, unlocking valuable information about how much sea levels may rise in the future in a warmer climate. warm.
The groundbreaking research focused on the genetic history of the Turquet’s octopus (Pareledone turqueti), which lives on the Antarctic seafloor, and what it could reveal about the geology of the region over time.
Tracing past encounters between the species’ various populations suggested that the ice sheet’s most recent collapse occurred more than 100,000 years ago during a period known as the Last Interglacial, something geoscientists had suspected but had been unable to confirm. definitely, according to the published study. Thursday in Science magazine.
“This project was exciting because it offers a completely new perspective on solving a long-standing question in the geoscience community,” said the study’s lead author, Sally Lau, a postdoctoral researcher at James Cook University in Australia.
“The DNA of animals alive today contains all the information about their ancestors (in the) past, so it’s like a time capsule,” he said.
The research team arrived at their findings by sequencing the DNA of 96 Turquet’s octopuses that had been collected by institutions around the world and through bycatch over the years. The oldest samples date back to the 1990s, but when sequenced, their genes provided what was essentially a detailed family tree going back millions of years.
Octopus family tree
The DNA analysis allowed the researchers to understand whether different populations of Turquet’s octopus had interbred and when that interbreeding had occurred.
“It’s like doing a 23andMe with the octopus,” Lau said, referring to the genetic testing company. “This information is passed from parents to children and grandchildren, etc.”
Today, Turquet’s octopus populations in the Weddell, Amundsen and Ross seas are separated by continent-sized West Antarctic ice shelves and cannot intermingle.
However, the study suggests that there was last genetic connectivity between these populations about 125,000 years ago, during the Last Interglacial, when global temperatures were similar to today’s.
This finding indicated that the West Antarctic ice sheet had collapsed during this time, an event that would have flooded coastal regions but opened up ice-covered areas on the seafloor that octopuses could occupy, encountering and breeding with members of the populations of Turquet. that were once geographically separated from each other.
“What makes WAIS important is that it is also Antarctica’s largest current contributor to global sea level rise. A complete collapse could raise global sea level by between 3 and 5 metres,” study author Jan Strugnell, professor and director of the Center for Sustainable Tropical Fisheries and Aquaculture at James Cook University, said in a statement. Strugnell first came up with the idea of using genomic methods to investigate whether the ice sheet had collapsed during the last interglacial.
“Understanding how the WAIS was configured in the recent past, when global temperatures were similar to today’s, will help us improve future projections of sea level rise,” he said.
Why octopuses?
The team chose this species of octopus for the study because the animals are relatively immobile: they can only crawl along the seafloor, meaning they are more likely to reproduce within their genetically distinct local populations. By contrast, a fast-moving marine species like krill would have more homogeneous DNA, erasing historical genetic connections, Lau said.
Additionally, the biology of the Turquet octopus was relatively well studied and scientists understand its DNA mutation rate and generation time, which are crucial for accurate molecular dating, Lau added.
Previous studies involving marine crustacean and mollusk species had detected a biological signature of ice shelf collapse with direct connectivity between the Ross and Weddell seas, Lau noted. But Turquet’s new octopus study was the first with enough high-resolution data and an adequate sample size to understand whether that genetic connectivity was driven by the collapse of the ice sheet or by a much more gradual movement of octopuses around of its edges.
Lau said his team’s genetic approach could not reveal exactly when the ice sheet collapsed or how long that event lasted. However, with fresh octopus samples and more advanced DNA analysis techniques, it might be possible to resolve those questions in the future.
“We would love to continue using DNA as a proxy to explore other parts of Antarctica whose climate history is not well understood,” he said. “We are constantly looking for new species to test these scientific questions.”
‘Pioneering’ study
In a commentary published alongside the study, Andrea Dutton, a professor in the department of geosciences 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, called the new research “pioneering.”
They noted that while geological evidence had been accumulating that the frozen expanse of the West Antarctic Ice Sheet may have collapsed during the last interglacial period, “the findings of each study come with caveats.”
Using a completely different data set to address this pressing question “raised some intriguing questions, including whether this history will repeat itself, given the current trajectory of Earth’s temperature,” they added.
Using octopus genomics was “an innovative and exciting way” to address an important question about historical climate change, said Douglas Crawford, a professor of marine biology and ecology at the University of Miami who was not involved in the research.
“This is a careful study with a sufficient sample size and a carefully examined set of genetic markers,” he added.
“It takes a challenging hypothesis and uses a completely independent data set that (ultimately) supports the collapse of WAIS,” he said by email.
For more CNN news and newsletters, create an account at CNN.com
