London, August 9 : Scientists at the State University of New York in Stony Brook have discovered that the marine snail Nucella lamellose can adapt its shell to defend against predators.
Lead researcher Paul Bourdeau studied this phenotypic plasticity in the Nucella lamellose-whose two main predators are the shell-crushing rock crab, Cancer productus, and Pisaster ochraceous, a starfish-in the San Juan Islands, Washington.
He reared wild-caught baby snails in the presence of different predators at the University of Washington's Friday Harbor Laboratories.
The researcher says that starfish feed by inserting their stomachs into the opening of a snail's shell and then flipping it back, sucking the partially digested snail with it.
As a response to this threat, Bourdeau adds, the young snail grows more elongated shell so that it can hide at the very tip, as far from the starfish as possible and perhaps far enough to withstand attack if discovered.
In the presence of crabs, according to the researchers, the young snail grows more rotund shells that can dissipate the force of the predator's crushing attack.
Consequently, the rock crab crushes hard.
"These are the meanest organisms I have ever come across," Nature magazine quoted Bourdeau as saying.
During the study, starfish and crabs were presented with a smorgasbord of equal numbers of snails from each type.
While the starfish ate five times as many of the crab-induced shapes, crabs ate almost twice as many of the sea star-induced shaped.
When the researchers raised the snails with the simultaneous presence of both predators, their shells followed the crab-defence shell design, indicating that the snails have evolved to prioritise predators, and that the crab is the most dangerous.