An international mission to save what many regard as the world’s most beautiful snails is underway in the UK and the animals’ native Cuba. The tree-dwelling molluscs, known as polymita snails, are prized for their incredibly colourful shells. Despite being protected, people collect them to turn into jewellery and other ornaments, which are internationally traded – illegally – for high prices. And this is driving the animals towards extinction. To try to better conserve them, evolutionary geneticist Angus Davison, at the University of Nottingham, has teamed up with researchers in Cuba to catalogue and study the snails, and sequence their genomes. For him, it was love at first sight, several decades ago…
Angus – They’re beautiful and they have an extraordinary variety of different colours: red, orange, pink, yellow, green, brown, black. And then on top of that, they have all different kinds of patterns which are overlaid on that. An individual is extraordinary in the way it looks, but then when you go to a place in Cuba and find some of them and they’re all different, it’s just mind-blowing, it’s amazing.
Chris – How large are they?
Angus – They are quite large. So some of the largest species would be approaching the size of a garden snail that you might see in this country.
Chris – And is that their downfall? They’re pretty, so they’re disappearing because people want them?
Angus – Yeah, that’s the irony, isn’t it? The reason I’m interested in them as an evolutionary geneticist is to understand the colour and the genetics and the beauty that brings to them. But that is also partly their downfall. So that means people are interested in them. People will collect them illegally, export them out of Cuba, where they’ll sell them for quite high sums of money. So that’s one of the reasons they’re endangered.
Chris – How did you get involved in them?
Angus – So I’ve been working on snails for a ridiculous number of years now, for 30, I think, or nearly 30 years. And if you open up any book of snails, you might see some quite pretty pictures of snails, and then eventually you’re going to see a book with these amazing Cuban Polymita snails in them, and that’s when your jaw just drops. You think, wow. So I was lucky enough to go to Cuba in, I think, 2001. For the first time, we collected samples of all of the species with the aim to try to initiate these studies, but the political situation then was too difficult. And so I had to leave the specimens in the country. And so it’s taken another 20 years since then, really, to get this project going. More recently, we worked with my Cuban collaborators. The Cuban Polymita won Mollusc of the Year in 2022, of which part of the prize for that was to have its DNA sequenced and assembled. So that’s kind of a starting point for a lot of the genetics that we might wish to do with the snails.
Chris – Is it just one species then, or is it a whole group of related species that all have this characteristic, this trait, and are all similarly endangered?
Angus – We believe there are six species, and I think that’s probably correct. The genetic studies that we’re undertaking will ultimately show whether there actually are six species or not. All the historical taxonomic studies have suggested there are six species. And knowing how many species is interesting from an evolutionary standpoint, you can try to understand how they came about, what species they evolved from. But it’s actually also important for conservation. So if there are six species, then of course you want to preserve six species. But if it turns out that you have a cryptic or hidden species, then you need to know that so you can preserve all of those species. And so you can’t always recognise the species just by looking at the outward shell.
Chris – Can you also use the genetics in the same way that in, say, Africa, we can look at where ivory has come from by using genetics? And that can help to bear down on illegal ivory trades. Could it form part and parcel of that for the snails?
Angus – That would be lovely, yeah. So I know that ivory study, and it’s just amazing work that they have done there. That’s exactly right. So we’re not doing that, but that would be a wonderful thing to do. So you could have a shell which has been illegally traded. There is probably what we would call ancient DNA within that shell somewhere. And you could then extract that DNA and work out where it came from. I think in the same way they did for the elephants, you could work out whether it came from a population that is there now – so still present and still alive – or actually the person selling it might claim that it was, say, harvested more than 50 years ago, and therefore it might be legal to trade it in some way or something like that. There’s further benefits of doing that, of course, because we’re studying the populations that remain today. There are populations that have gone extinct, but we don’t know really how much of the underlying genetic diversity has been lost. So you could, for example, use museum specimens to then get a picture of everything that was there in the past as well.
Chris – And what about initiatives like captive breeding programmes and so on to try to boost numbers and therefore conserve what we do have before we lose any more?
Angus – Yes, that’s a good idea. So what my Cuban collaborator is doing is trialling that at the moment. So we’re not quite at the stage where we think that’s necessary, but if it ever does become necessary, then of course you need the methods in place already so that you can take the few remaining into captivity. I have to say, though, it is difficult. So one of the reasons the shells are colourful is probably because they live in trees. Tree snails themselves are quite difficult to keep in captivity, in my view. At the same time, there are other reasons that bring them to captivity, so we don’t really know what they eat. So of course he can trial to see what they eat. So it kind of adds to the picture of their biology as well at the same time.