The Japanese white-eye is one of the most
popular airplane models for snails.
The airplane is, arguably, one of the greatest inventions of humankind, shortening travel times and bringing disparate cultures together. But it turns out that we’re not the only ones to take advantage of flying vehicles. Researchers in Japan have now learned that a certain land snail, Tornatellides boeningi, can quickly travel great distances by hitching a ride in the guts of birds.
The surprising discovery all began a few years ago. Knowing that seeds are often dispersed by fruit-eating birds, scientists from Tohoku University wondered in 2008 if the same could happen with snails. So, naturally, they took a close look at the feces of birds in the Bonin Islands. They found snail remains—unbroken shells and melted bodies—in the poop of Japanese white-eyes and brown-eared bulbuls, and hypothesized that the snails could survive bird digestion under the right conditions.
They were right. In their recent study, published in the Journal of Biogeography, the researchers fed 119 adult snails to Japanese white-eyes and 55 snails to brown-eared bulbuls, and roughly 15 percent of the snails came out alive. (Covered in poop, yes, but alive.) In fact, one of the snails gave birth to juveniles right after being egested. The researchers believe that passing through the gut of birds may be a cue for pregnant snails to give birth, as this would enhance the snails’ probability of colonizing new areas.
The biggest factor for snail survival was body size: little T. boeningi snails suffered no damage to their shells, whereas other, larger snails did. The researchers think that T. boeningi may be able to produce mucus that protects them from the birds’ digestive fluids, but this is a topic for future research.
Okay, T. boeningi can survive being eaten by birds, but are the snails really dispersing this way? To find out, the researchers performed genetic analyses of snails from 27 sites on Haha-jima Island. If the snails are not traveling long distances via bird, then the researchers should have found that snail populations near each other are genetically more similar than those further apart. Instead, the researchers discovered a high level of gene flow between populations, suggesting that seemingly isolated snail groups were still mating and swapping genes despite the distances between them.
A few years ago, another study showed that pond snails may be able to survive being eaten by fish. So, these crafty little slimeballs have their own submarines in addition to their own airplanes.