Nestled in cracks and crevices in coral reefs off the coast in South East Asia, so-called disco clams are busy putting on a light show. But unlike many animals in the ocean that produce their own light, a new study finds that these flashy mollusks catch and reflect ambient light for their displays.
Found throughout the Indo-Pacific, Ctenoides ales is a striking saltwater clam with colorful tendrils and a peculiar talent long known to divers: It produces flashes of light that at first glance look like flickers of neon or ripples of electricity. Hence its nickname, the “electric”, or disco clam.
Belonging to mollusk family known as Limidae which comprises of only bivalve mollusks which are made up of scallops, clams, oysters and mussels that have a shell consisting of two rounded plates called valves joined at one edge by a flexible ligament or hinge.
The Electric Flame Scallop ranges in size from 1 inch to 3 inches when reaching maturity and is instantly recognizable by its soft parts being a flame red color, with several bright red tentacles protruding from the open valves (shell). What makes this creature even more fascinating is that it seems to create bluish white electricity which can be seen shooting across the mantel like lightning bolts quite visibly in the dark.
While the purpose of the Electricity generated by this creature is unknown, it makes a remarkable spectacle for any night dive where even in the darkness; you can see the flicker of bluish electricity bolts flowing through the scallop’s filaments. For Underwater photography an electric flame scallop is truly a delight to photograph. During the day, the bio-luminescence isn’t very apparent, which is why electric scallop sightings are more spectacular at night.
How the ‘Disco Clam Lights up underwater?
Lindsey Dougherty, a graduate student at the University of California at Berkeley, first encountered the clam during a dive in Indonesia and quickly became fascinated by it. So she decided to devote her PhD to figuring out how the disco clam produces its signature flash.
The animal’s impressive light show was long thought to be an example of bioluminescence—or an organism’s ability to produce light through chemical reactions—until research in the 1990s discovered it was actually a matter of scattering ambient light.
Dougherty and her team found that the flashing effect was due to the unique structure and composition of the clam’s fleshy lip. That lip, or mantle, contains two distinct tissue types that enable it to scatter ambient light.
The mantle edge is filled on one side with nano-size spheres made of silica, said Dougherty. “Silica is very rarely used by animals but has a high refractive index, which makes it a great reflector.”
The mantle’s other side is very good at absorbing light, resulting in the alternating, or flashing, light effect when the lips flap open and closed. Bivalves are filter feeders, so their shells are constantly opening and closing in order to let water pass over their gills to pick up food, explained Dougherty.
“The tissue furls and unfurls back and forth to expose the two distinct sides about twice a second,” she explained. When they’re startled—by a fake predator in a lab test, for example—”their flash rate jumps up to four times a second,” she added. The researchers studied the phenomenon using high-speed video and other tools.
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