The disco clam has a unique light show it performs, providing the species with its dance-inspired name.
Lindsey Dougherty, a graduate student at the University of California Berkeley, believes she may now know the secret to their unique display.
The avid diver first encountered disco clams in 2010, during a dive in waters off Indonesia. She was under water with her sister and mother when they saw the animals, the two sisters began disco-dancing under water.
"I've dived with humpback whales and great white sharks. But when I saw the disco clam, I was enamored. I said then, 'I'm going to do a Ph.D. on the disco clam,'" Dougherty said.
Disco clams are only about two inches long. The source of their unique show is not bioluminescene. That chemical process accounts for the lights of fireflies and plankton. Dougherty quickly found the chemical reaction, similar to a glow stick, does not account for the unusual show carried out by the disco clam.
One edge of the clam's mantle (lip) is covered in small, highly reflective, spheres that cause light to shine off its surface. As the animal's tongue flicks back-and-forth twice a second, it blocks and exposes the mirror-like surface. This creates a flashing motion, as ambient light is repeatedly reflected and blocked. The rear part of the mantle is colored dark blue, adding to contrast between the two states. The study found no evidence of other species using a similar system.
Disco clams, otherwise known as electric clams or Ctenoides ales, make their homes 10 to 150 feet beneath the surface, in tropical Pacific locations.
Dougherty believes the flashing behavior may be used by the clams to communicate with other members of its species. Other theories say the flashing lights may attract prey or to frighten off predators.
Disco clams have 40 eyes, but Dougherty is uncertain whether the bivalves can see the light emitted by other members of its species. As part of her continuing research, the team is raising disco clams in tanks. Researchers hope to determine how the animals communicate with each other using chemical signals, or by visual cues. Response to artificial predators is also being tested, to measure reactions.
Researchers working with the graduate student used high-speed photography, X-ray spectroscopy and computer simulations to uncover mechanism the clams use to create the show. They released a video about their work.
Study of the disco clam and the mechanism behind its unique flashing behavior was profiled in the Journal of the Royal Society Interface.
