Green means danger for one flashy mollusc

A little-known sea snail may produce flashes of green light to scare away predators according to new research published in Proceedings of the Royal Society B this week. Scientists at at the Scripps Institution of Oceanography at UC San Diego have been studying the mysterious flashes of dazzling bioluminescent light produced the mollusc.

The mollusc, Hinea brasiliana, has a tiny "bioluminescent" body part lodged permanently within its shell. The scientists have found that the shell amplifies the light, and the faint glow it produces illuminates the whole shell surface. They believe that the display could be a deterrent to ward off potential predators by using diffused bioluminescent light to create an illusion of a larger animal.

The lead researcher, Dr Dimitri Deheyn, describes how  H. brasiliana set off its glow, likening it to a burglar alarm going off, when the snail was confronted by a threatening crab or a nearby swimming shrimp.

Discovering how the snail spreads its light came as a surprise to the researchers as this species features opaque, yellowish shells that would seem to stifle light transmission. But in fact when the snail produces green bioluminescence from its body, the shell acts as a mechanism to specifically disperse that light. What is also interesting is that it is colour-specific. If you shine a red or blue light through the shell, it doesn’t work. It only works for the blue-green light that the snail produces.

Studies into such adaptations are of keen interest in optics and bioengineering research and development industries. The team now plans to study the shell in detail, to find out how it works and possibly copy its specialised light-amplifying structure.