Ryan Hechinger, a research biologist with the Marine Science Institute at UCSB, recently discovered an unlikely creature has been utilizing air travel for millennia. Along with his colleagues, Hechinger found that horn snails have hitched free rides from ocean to ocean via unsuspecting migrating birds.
According to the article — “Flying shells: historical dispersal of marine snails across Central America,” published Sept. 14 by Proceedings of the Royal Society: B — these snails were able to secure transport from the Pacific Ocean to the Atlantic and back by residing undigested in the stomachs of migrating birds or by affixing themselves to the birds’ legs.
The snails’ hitchhiking ability is made possible in some instances because they are able to survive ingestion by the shorebirds. Upon arrival, the snails are then dispersed in the birds’ feces.
“Just as people use airplanes to fly overseas, marine snails may use birds to fly over land,” co-author Mark Torchin said in a press release. “It just happens much less frequently.”
The scientists compared the mitochondrial DNA of two sister species of marine snails — Cerithideopsis californica and Cerithideopsis pliculosa — and found that, despite geographic separation, the two species have periodically been in contact.
These two snail species are believed to have been separated by the rise of the Central American Isthmus of Tehuantepec in southern Mexico three million years ago. Genetic differences between the snails suggest that two successful dispersal events between the Pacific and the Atlantic occurred after the creation of the isthmus.
Since the two snail species cannot interbreed due to their different genetic make-ups, scientists have been able to conclude that cross-terrestrial migration must have occurred. By imploring molecular dating techniques, Hechinger and his colleagues found that the first such event occurred around 750,000 years ago, while the second event took place about 72,000 years ago.
In light of this discovery, the possibility that many other species have also utilized birds to cross geographical barriers that were previously thought to be impassible, such as the Central American Isthmus, is quite real.
“Not only snails, but many intertidal organisms may be able to ‘fly’ with birds,” Osamu Miura — the first author of the paper and assistant professor at Japan’s Kochi University — said in a press release.
The discovery of these hitchhiking snails has many implications, especially the introduction of new genes into native populations.
“There is a chance that the hitchhiking snails benefited native populations by bringing in new genes that helped them resist common parasites that castrate the snails and keep them from reproducing,” Hechinger said.
Further studies of these snails and other unlikely migratory species could allow scientists to better understand species dispersal, the introduction of new genes into native populations and the formation of new species.