'Disco clam' reveals groovy sea floor moves

A sea floor diva known as the "disco clam" has revealed the secrets of its dazzling moves.

The funky mollusc, which lives in crevices at depths of 3-50m, earned the name from its vivid rhythmic display of flashing mauve light.

Experts first thought the light show was just another example of bioluminescence, but new research shows it is groovier than that.

The disco clam, real name Ctenoides ales, uses microscopic glass beads to scatter reflected light from along the lips of its two shells.

High-speed video shows how the clam unfurls and furls its lip edge in a wave-like motion, alternately exposing the reflective silica spheres and non-reflective light-absorbing tissue.

Scientists who subjected the clam to a battery of sophisticated tests discovered that the beads are the perfect size to maximise light scattering.

Details of the research appear in the Journal of the Royal Society Interface.

The US scientists, led by Lindsey Dougherty from the University of California at Berkeley, wrote: "To the best of our knowledge, C. ales is the first animal to use silica as a scattering structure via intracellular nanospheres. Indeed, it is unusual to see silica secreted by animals for any purpose."

The researchers believe the flashing serves as a signal, but are still investigating why it evolved.

One theory is that it helps juvenile disco clams find each other so they can settle in small colonies.

Studies have shown moving a stimulus towards the clam causes the flash rate to increase.

The light is also visible to many reef fish, cephalopods such as squid, and crustaceans. This suggests it might also act as some kind of a deterrent to would-be predators.

- PA