Footnotes for The Jumping Snail
¹ The jumping snail usually jumps two or three times in a row. Afterwards, the little animal is spent, appearing visibly sluggish (or snailish). Snails are obviously not high-metabolism creatures. The sudden, fast thrashing movements required for the jumping snail to get airborne would be like a human repeatedly pole-vaulting over hundreds of metres, no doubt leaving them exhausted, gasping for breath.
The jumping snail extends two thin, flattened lobes out of its shell, spreading them across the outer surface. These aren’t wings; they do not help the snail jump. Instead, they are thought to be respiratory organs that supply the extra oxygen it needs to recover from its extraordinary exertions, and to make the snail ready to leap again.
² When researchers analysed key DNA markers (specifically the mitochondrial COI gene) from jumping snails collected across Brazil and Argentina, they found their DNA sequences were 100% identical to reference samples from their native home in Japan.
Although this does not mean that entire genomes are identical between jumping snails in Japan and those in South America — they’re almost certainly not — it does indicate that these snails have experienced little genetic change. This could be a result of recency: jumping snails only arrived in South America in 2013. It could be due to a “single founder effect,” with the large invasion across South America possibly starting as just a tiny handful of snails (or perhaps even just a single individual). Or this lack of genetic diversity may be due to the snail’s ability to reproduce uniparentally. Likely, it is a combination of all these factors.
“As for the low genetic diversity often found in introduced populations,” says Salvador, “we do not yet know how much this affects individual animals within those populations. We simply do not have enough data at this point. However, it is clearly not detrimental to the population as a whole, given how rapidly these snails are spreading.”
³ In these forests, the snail has been found living directly alongside the flea-frog (Brachycephalus hermogenesi). This minuscule frog is known to be an ecologically demanding species that only thrives in well-preserved native habitats, indicating that the snail is successfully establishing itself in environments previously thought to have strong biotic resistance against invaders. This raises the question: is the snail capable of breaking through such strong biotic resistance, or is the resistance of these “well-preserved” environments maybe not as strong as we assumed?
⁴ While doing fieldwork in Brazil, malacologist Dr. Janine Oliveira Arruda watched a woman open a bag containing a flowering seedling, intending to plant it in a garden at the edge of a wild fragment of Atlantic Forest. Hidden inside the bag was an exotic slug species. “Humans transport these species,” says Arruda, “and if they possess sufficiently plastic ecological traits, they are able to survive and establish themselves.”
⁵ Like any survey method, however, citizen science has its blind spots. Dr. Díaz suspects that the absence of recorded sightings in rural regions of Argentina reflects a shortage of active iNaturalist users — rather than a true absence of jumping snails. Citizen science data can often reflect the presence or absence of users, rather than the presence or absence of a species. Nonetheless, platforms like iNaturalist are still incredibly useful tools in tracking the spread of invasives, and they only become more accurate as more people use them.
“It does not replace or substitute for traditional fieldwork,” Díaz emphasises. “It merely complements it and provides an idea of the exact locations where these species are present for subsequent search and analysis.”
