Frozen in time: Researchers identify microbes that lived in guts of 100-year-old snails

The guts of 100-year-old snails have been frozen in time. Ecologists at the University of Colorado Museum of Natural History have made history, as for the first time ever, modern, DNA-screening tools were used to identify the microbes that once lived in the guts of animals that have been dead for a century.

Dr. Bridget Chalifour, the study’s author, says these microbiomes offers a window into how animals interacted with their environments in bygone eras. “We’ve learned that samples from 50 or 100 years ago have just as much viability to answer modern, ecological questions as samples collected just two years ago,” she explains in a statement.

To conduct the study, ecologists collected 55 Rocky Mountain snails between 1920 and 2018. They included three snails Colorado scientist Junius Henderson plucked in July 1920. These snails are the size of a thumbnail and only come out when it’s wet. They eat leaves and other plant matter.

“When it’s raining, they’re usually out grazing on rocks or trees at places like Eldorado Canyon in Boulder,” explains Dr. Chalifour.

The snails were then placed in ethanol.

“Museum specimens and artifacts are the next best thing to a time machine,” says Jingchun Li, study co-author and curator of invertebrates at the museum and assistant professor of ecology and evolutionary biology. “With many such specimens and data, we can ask how the changing climate has shaped mountain plant communities through time. We can detect what organisms survived mass extinction events.”

Even though the microorganisms within the snails’ guts had been dead for decades, researchers were able to sequence what was left of their DNA and found they had been previously bursting with life. They identified more than 7,000 organisms, mostly bacteria, hiding inside each snail.

“It’s exciting for me because I’ve now deposited a lot of samples into the museum,” says Dr. Chalifour. “I like to think about what people may do with my snails in 15 years.”

According to Dr. Chalifour, the the snails’ microbiomes shifted a bit over the century for reasons that aren’t known. The 100-year-old snails housed a lot of bacteria belonging to the genera BradyrhizobiumAlicycliphilus and Cloacibacterium. However, the snails from 2018 were partial to Flavobacterium and the families Chitinophagaceae and Cerasicoccaceae.

Dr. Chalifour adds that droughts and wildfires may be squeezing these wet-weather animals out of their former habitats. “A lot of the populations we have in our collections aren’t there anymore,” she says.

The study is published in the journal Microbiome.

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