A scientist collected snails in 1920; A century later, their guts revealed a hidden world

In July 1920, naturalist Junius Henderson was walking along the Dakota Hogback, a sandstone ridge near Boulder, Colorado, when he came across Rocky Mountain snails moving across the ground. He collected some of them and took them back to the laboratory, where they were preserved.

There was nothing unusual about the exercise at the time. Naturalists routinely collected specimens to document the plants and animals around them. Henderson could not have known that the snails would one day help scientists investigate a world too small to see without a microscope.

More than a century later, researchers examined the preserved animals and recovered DNA from microbes that had lived inside their digestive systems. The study, published in the journal Microbiome on June 29, 2022, showed that even specimens collected during Henderson's lifetime could retain useful evidence of their former microbial communities.


The discovery also raised a larger question: what can old museum collections tell us about the natural world that has changed around them?

A century inside a museum jar

The research team, which included Bridget Chalifour, Leanne Elder and Jingchun Li from the University of Colorado Boulder, studied 55 Rocky Mountain snails collected between 1920 and 2018. Some specimens had been preserved in ethanol for decades. The animals were long dead, but their remains still contained traces of microbial DNA.

The researchers identified evidence of more than 7,000 organisms, mostly bacteria, in the snails' guts. Many of the bacteria belonged to groups associated with breaking down complex organic material, including cellulose found in plant matter.

The finding mattered because a snail's gut is more than a container for food. The microorganisms living there can help researchers understand how the animal interacts with its environment. The team found that the microbial communities varied across the specimens. Where the snails had lived was an important factor in those differences, accounting for about 20% of the variation observed in the study.

The results also showed that preserving an animal in a museum does not necessarily erase all the biological information it carries.

What the old specimens could tell scientists

The study compared snails collected over nearly a century, giving researchers an opportunity to investigate changes that could not have been measured directly in 1920. Henderson's specimens included three snails he had collected himself. The modern team could compare them with animals gathered in later decades and examine how their microbial communities differed.

There were changes in the bacteria detected in the older and newer specimens, although the researchers could not attribute every difference to a particular cause. The animals' locations appeared to matter more than the collection dates alone.

This distinction is important. A difference between two sets of preserved specimens does not automatically prove that climate change caused it. Habitat, diet, local environmental conditions and other factors can influence microbial communities.

Still, the work demonstrated a useful possibility: collections gathered for one purpose can answer questions their original collectors never imagined.

Museum shelves are often treated as storage for objects and specimens from the past. In reality, they can function as a record of biological conditions that existed before modern environmental monitoring became common.

A search for snails that were no longer easy to find

Chalifour searched parts of Boulder County where Henderson had collected the snails a century earlier. She could not find the animals in the locations she investigated.

The researchers noted that drought and wildfires may be putting pressure on these moisture-dependent snails. But the field search did not establish that climate change alone had caused their absence from those particular sites.

Rocky Mountain snails depend on suitable local conditions, and their distribution can be affected by several environmental factors. A failed search also does not prove that a species has disappeared from an entire region.

Even so, the result made the old specimens more than a laboratory curiosity. They provided a reference point for investigating wildlife that may have become harder to find.

The contrast is striking: Henderson's specimens preserved evidence of animals encountered during an ordinary field trip, while a modern researcher returned to some of those places and came away without finding the same snails.

Why a forgotten collection matters now

Scientists cannot travel back to 1920 to sample the soil, vegetation or microbes surrounding Henderson's snails. But preserved specimens can offer a partial record of the biological communities that existed at the time.

The method could also help researchers study other historical collections, provided enough usable biological material remains. Its value is not limited to snails. Collections of insects, fish and other animals may preserve information that becomes accessible as DNA-analysis techniques improve.

There are limits. Museum specimens represent the places and species that collectors happened to sample, not a complete inventory of past biodiversity. Preservation methods can also affect what scientists are able to recover. But the study showed why old collections deserve attention beyond their original purpose.

Henderson collected the snails because they were part of the natural world he was documenting. A century later, the specimens offered clues about organisms that lived inside them and the environments they inhabited.

The snails could not tell researchers everything that had changed in the Rockies. They could, however, preserve a biological trace of a world that no longer looked exactly the same. Sometimes, the past does not survive in a dramatic fossil or a buried city. It survives in a museum jar, waiting for science to learn how to read it.