A new study reveals why the disco clam, a tiny mollusk renowned among pet lovers for its underwater light show, uses a glimmering underwater display. Researchers found that the clam’s flashes are meant to both scare predators away and to attract prey.
The 2.8-inch-long disco clam also known as the electric flame scallop or electric clam is a salt water clam that dwells in the Indo-Pacific’s reef. It is the only bivalve mollusk to have light displays.
Marine researchers previously believed that the small clam’s body was emitting the lights. But, a recent study showed that the clam’s lips have shiny silica spheres that reflect the ambient light.
“When most people imagine clams, they imagine the things that make clam chowder. These clams are very different. They’re reef-dwelling, they have bright-red tentacles, they have gills that stick out, they live in little crevasses [and] they are the only species of clam that flashes,”
said Lindsey Dougherty, lead-author of the study and marine biology researcher at the University of California, Berkeley.
During the study, researchers analyzed the behavior of a disco clam placed in an aquarium. To learn more about how disco clams react to an incoming predator, Mrs. Dougherty and her team used a Styrofoam lid to simulate a predator attack.
When the Styrofoam lid was getting closer to the disco clam, its flashing rate almost doubled, from 1.5 times to 2.5 times per second. Scientists also found that disco clams have a back up plan when they get attacked. Besides intimidating predators with their flashes, these tropical clams also release sulfuric acid into water.
Researchers used calcium chloride to measure the amount of sulfuric acid present in water. After mimicking a predator attack, there was about twice more sulfuric acid nearby the clam than before.
Scientists say that more tests are required to verify their theory about the sulfuric acid. However, disco clam is not the only marine species to employ such strategy. Some snails and other clams do it too.
After the Styrofoam lid test, researchers brought in a living predator – a peacock mantis shrimp. The shrimp tried to open the disco clam, but after a few minutes it suddenly backed off and left the clam alone.
“That is very strange behavior [for the mantis shrimp]. They’re very aggressive critters, and to have a clam open and flashing, and the mantis shrimp not attacking, is very weird,”
Mrs. Dougherty explained.
Researchers believe that the disco clam used the sulfuric acid or other agent to keep the shrimp at bay.
The team also found that, when its food (plankton) is close by, the disco clam intensifies its flashes to attract it. So, researchers believe that the clam also uses its flashes to attract prey. However, is very hard to tell if that is the case in an aquarium. So, Doughtery’s team now plans to further study disco clam behavior in its natural habitat in Indonesia.
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