By Alexandre Fuster, Postdoctoral researcher at Université de Sherbrooke and the Insectarium of Montreal

What if a snail shell could tell us not only where a snail lived, but also who it had interacted with?

This question sounds strange, but it pushed me into one of the riskiest and most exciting adventures of my PhD. Thanks to the CSBQ Excellence Award, I travelled to the University of Idaho to work with Dr. Christine Parent’s lab and explore a new idea: using museum collections of Galápagos land snails to reconstruct hidden host-parasite interactions.

The story began with a fascinating discovery. Some land snails can kill parasitic nematodes using their shells. Yes, their shells. The same structure we usually think of as protection against predators or drying out can also become a defensive weapon against parasites. In evolutionary biology, this is called co-option: when a structure that evolved for one function is repurposed for another. Feathers, for example, likely had early roles in insulation or display before becoming central to flight in birds.

In these snails, nematodes become trapped and encapsulated inside the shell. This might sound like a weird natural history detail, but for us, it opened a door. If nematodes remain preserved inside shells, could we recover their DNA from museum specimens? And if we could, could we reconstruct which parasites interacted with which snail species across islands, habitats, and evolutionary history?

For my research on Naesiotus, the largest radiation of land snails in the Galápagos, this possibility was thrilling. These snails are endemic, diverse, and distributed across a clear island context. Their evolution, traits, and habitats have been studied for years, but one major piece was missing: their ecological interactions. If we could recover parasite DNA from shells, we could build a host–parasite network and ask how interactions relate to diversification.

The project was risky from the start. We did not know whether Naesiotus shells would contain encapsulated nematodes. We did not know whether DNA could be extracted from those tiny traces either. Even obtaining snail DNA from old shells can be challenging, and here we were hoping to recover parasite DNA from microscopic structures preserved inside them. There were no ready-made protocols. No guarantee. Just an idea, a collection, and a lot of curiosity. 

The CSBQ award helped me to follow that idea. In Idaho, I began working with Ian Oiler, a PhD student in Christine’s lab, and Jane Dosart, manager of the lab. We opened hundreds of tubes containing shells collected from volcanoes across the Galápagos Islands: unique, endemic, and often endangered specimens, each carrying a small piece of natural history. 

At first, we were simply searching for signs of encapsulated nematodes. Then we found one. Then another. Then another. Soon, the excitement became contagious. We were astonished to see encapsulations across all the species we examined. Tiny structures inside shells became evidence of past encounters between hosts and parasites. It felt like opening biological time capsules, one shell at a time. 

The month in Idaho was intense: long days, non-stop lab work, and constant problem-solving. It was also deeply stimulating. I exchanged ideas with researchers working on phylogenetics, evolution, and bioinformatics. As an ecologist, I often use phylogenies as tools, but being surrounded by people who develop these methods reminded me that phylogenetics is an entire discipline of its own. 

Then came the moment of truth: DNA extraction and sequencing. Normally, one would carefully test primers, optimize protocols, and sequence a small pilot set first. But we had limited time, and this project was already a leap into the unknown. We made our best bet, using primers and pipelines from recent work on nematode DNA, sent the samples off, and waited.

Those weeks felt long. Would there be enough DNA? Would the primers work? Would we recover anything meaningful?

When the results came back, they were better than we had dared to expect. It worked. And it worked remarkably well.

We recovered a large diversity of nematodes associated with Naesiotus species, including many taxa previously undocumented from the iconic biodiversity of the Galápagos. From shells sitting in collections, we reconstructed a hidden host–parasite network across the archipelago and began testing how ecological interactions and diversification are connected – if you are curious, this work is now available as a preprint.

Perhaps the most exciting part is that this approach does not have to stop with Naesiotus.

Many land snail radiations exist on oceanic islands around the world, and many are represented in museum collections. If encapsulated nematodes occur in other systems, shells could become archives of ecological interactions across space and time. 

This project also taught me something I would like to share with other students: curiosity becomes much more powerful when it is shared. 

The idea began because I came across the work of Robbie Rae, whose research on snail–nematode interactions fascinated me, and I wrote to him. That first exchange helped turn a strange observation into a possible project. But curiosity alone was not enough. The project became possible because supervisors, collaborators, students, and technicians were willing to be curious with me. None of us knew whether it would work. 

For me, this experience was a reminder that curiosity is worth following, especially when it brings other people into the question. Write to those whose idea made you think differently. Ask the strange question. Talk to people before the idea feels fully polished. Some ideas will not work, of course. But sometimes, if you find people willing to be curious with you, a risky intuition can become a discovery. 

The story is still unfolding. The Galápagos National Park has invited us to present this work at its 7th Science Symposium, and we are now discussing an exhibition at the Charles Darwin Foundation to showcase the hidden complexity of biodiversity: the world of parasites, the evolutionary creativity of snails, and the enormous value of scientific collections. 

Museum specimens are often seen as records of the past. But sometimes, they also contain the discoveries of the future.