Of snails and community science: how iNaturalist can help us know more about gastropods

Of snails and community science: how iNaturalist can help us know more about gastropods

Snails and slugs are some of the most threatened animals on our planet today and their biodiversity is still vastly uncharted. In the digital age, community science platforms such as iNaturalist pose an interesting perspective to gather new information on these organisms through user-submitted photos and data. Using Brazil as a case study, our new study explores the potential of iNaturalist as a source of biological data on rare snails and slugs. Undergrad student Rafael Masson Rosa reports on some new discoveries and recent outcomes from the study.

iNaturalist is a community science platform in which users can post photos of organisms they’ve sighted, including data on the time and place of the observation. The platform, accessible through both a mobile app and a dedicated website, musters a thriving community of people who frequently post and identify observations. It serves as a way to both educate people about their local biodiversity and generate useful data on the observed species.

Data from iNaturalist has been used in scientific research before, helping to map little-known species and even leading to the discovery of species new to science.

With that in mind, we decided to investigate which information we could gather from iNaturalist about land snails and slugs. These animals are severely endangered and still poorly understood – especially in tropical regions, where they are most diverse. So, we used Brazil as a case study and reviewed all observations on Brazilian snails and slugs posted on iNaturalist.

The study was published in the academic journal PLOS One and is freely available online. Some of our most interesting results are shown below.

Found alive for the first time

The description of snail species based only on dry empty shells is a common practice. For some species, living individuals have never been documented and nothing is known about their appearances aside from the dead shells.

Surprisingly, we identified quite a few of those cases. The most striking one is the megasnail Megalobulimus pergranulatus, which shows a unique (and previously unknown) colour pattern on its soft body.

A red and grey snail with a dark shell that has a red trim
Megalobulimus pergranulatus, previously known only by its shell, has several observations on iNaturalist showcasing the peculiar blueish-grey and orange colour pattern of its soft body. Photo by Marco Silva, via iNaturalist, CC-BY-NC 4.0

Potential new species

Amazingly, two potentially new species were detected among the observations we analysed. While we can not say for sure they belong to new species without a thorough analysis of actual specimens, both these snails are “oddities” that don’t quite fit any other known species.

A green-grey snail with a dark shell that has a green trim sitting on muddy ground
A potentially undescribed species of the megasnail genus, Megalobulimus, was photographed in southern São Paulo state. There are at least four other observations of this mysterious species, all of them from the same region. It is distinctive by its shell structure and intense black colour, differing from all other Megalobulimus species. Photo by rondon, via iNaturalist, CC-BY-NC 4.0
An undetermined species of the genus Plekocheilus was photographed in Alagoas state. There are at least three observations of this species in the same location. Like the example above, this snail doesn’t quite match any known species of Plekocheilus and its location is also unusual for the genus. Photo by Carlos Otávio Gussoni, via iNaturalist, CC BY-NC 4.0

Ecology and conservation

Besides the most striking discoveries, there were also plenty of interesting records on iNaturalist. Most of the observations highlighted by us on our article consist of records of native species outside their previously known range. But some observations are new records of ecological interactions and of rare species thought to be extinct.

A snail of the genus Scolodonta preying on another snail, photographed in Rio de Janeiro state. In the past, there has been a debate as to whether scolodontid snails, such as Scolodonta, were carnivorous or not. Now we have photographic evidence. Photo by Rogerio Dias, via iNaturalist, CC-BY-NC 4.0
A snail of the genus Cochlorina being preyed upon by the terrestrial flatworm Obama burmeisteri, photographed in Rio de Janeiro state. Terrestrial flatworms are notorious predators of land snails. Photo by Rogerio Dias, via iNaturalist, CC-BY-NC 4.0
A harlequin snail, Leiostracus carnavalescus, photographed in northern Espírito Santo state. This species was originally described in 2016 from a small fragment of Atlantic Forest that has since been devastated. This led the scientists who described it to face its possible extinction. Fortunately, there are now a couple of observations of live individuals on iNaturalist, indicating that the species still survives – for now. Photo by Alana Scheidegger, via iNaturalist, CC-BY-NC-SA 4.0

Potential uses elsewhere

While our study focused on the land snail fauna of Brazil, it serves as an example of how iNaturalist can bring relevant data for studies in general.

Tropical countries, where most of the biodiversity is located, are the most understudied regions in the world when it comes to terrestrial gastropods (and many other invertebrate animals). The lack of data on the fauna of these regions is particularly worrying when considering that snails are perhaps the most endangered animals nowadays, having the highest number of recorded extinctions of any animal group. As such, any new tool that can help us collect data on these animals is welcome, and iNaturalist has great potential to aid us in this.

The methods of our study can be easily applied for any terrestrial animal group and any country or region, provided that there are relevant observations for it on iNaturalist. It is clear that the platform, as well as community science in general, holds great potential to aid in inventorying biodiversity, and for this we must thank all users who take their time to take pictures of the fauna and publish them online.

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  1. I can also vouch for the potential scientific value of inaturalist. It is a great resource, with the main limitation being
    that the records are photographic only. This is not a problem for taxa that are photographically definitive, but
    not so good for taxa that are not. However, the photos can at least provide an alert, and their
    scientific value is sometimes realized when the photographers can be persuaded to obtain voucher material.
    I was fortunate in one instance where after three years specimens were obtained by some of the photographers and this effort led to verification of a new ghost moth species in northern Mexico (results available at https://zoonova.afriherp.org/documents/Grehan%20et%20al%202022%20ZN%2019%20Phassus%20NE%20Mexico.pdf).

    While inaturalist may be called ‘citizen science’ the ‘science’ part may require specimen based verification, which unfortunately in many cases is not possible (some photographers do not want to get involved with specimen collection, even if something new turns up). I can also vouch for the biological information of photos sometimes being useful. There is a unique biological behavior recorded for some South African ghosts moths for which identification is not possible, but recently a moth was reared by a photographer hat should soon arrive for direct examination and identification.

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