The Ctenoides ales, a saltwater clam that thrives in the underwater caves of the Indo-Pacific ocean, gives a visual treat of light shows with the shiny silica spheres in its lips that reflect lights.

Why these marine creatures , also known as the disco clam, produce flashy shows underwater is a mystery but a group of researchers had three hypotheses that could help explain the clam's flashy behavior.

Lindsey Dougherty, a marine biology doctoral candidate at the University of California in Berkeley, and colleagues wanted to know if the clams flash to drive away predators, attract a potential mate, or lure a prey so they conducted experiments with disco clams in an aquarium.

The researchers observed that when they placed an object that appeared like a looming predator in the aquarium, it triggers the clams to produce more flashes. Their flash rate increased from 1.5 times per second to 2.5 times per second when the "predator" was nearby.

The researchers also found that the creatures may use sulfuric acid to keep away predators albeit they still need to conduct further tests to verify this. Many marine creatures, however, including other clams and some snails are known to secrete sulfuric acid when they are threatened. Dougherty said that this substance could be crucial in the clam's defense strategy.  

"If you're flashing and saying, 'I'm distasteful; don't eat me,' that's one thing, but you have to sort of back it up," Dougherty said.

The researchers also introduced phytoplankton prey into the aquarium and observed that the flash rate of the clams increased when they sensed the presence of the prey. Many plankton species are attracted to light but it is still unclear if the species that the clam preys on can see its flashing. The researchers also plan to go to Indonesia to conduct studies of the disco clam in their natural habitat because testing the creature's eating habits in an artificial environment is difficult.

Dougherty and colleagues ruled out that the  2.8-inch-long clams use their light to attract a mate because when they examined the proteins and structures on the creature's eyes with a microscope, they found that the disco clam's vision is so poor it cannot observe the displays produced by other clams. This suggests, though that these marine invertebrate are not visually attracted to each other.

The findings of the study were presented at the 2015 conference of the Society for Integrative and Comparative Biology in West Palm Beach on Jan. 4.

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