Photograph by David Fleetham, Alamy
A bubble-rafting violet snail feeds on a Portuguese man-of-war in Hawaii.
Churchill and colleagues have a theory for how the snails' bottom-dwelling ancestors took to rafting.
They hypothesize that at some point, a female living near the coast may have been briefly carried—along with her egg mass—by waves. This led to temporary periods of rafting. Eventually this ancestor lineage evolved the ability to create bubbles with their mucus and make rafts on purpose.
"Obviously, the ability to add bubbles probably didn't evolve overnight," Churchill emphasized. "It would have been over some period of time, and eventually that lineage became successful at adding many bubbles together to create a float."
The evolutionary transition from bottom-dwelling to bubble-rafting gave snails access to new food sources at the surface, where they are relatively free from competition, Churchill said.