If you are ever lucky enough to dive and see underwater caves of the Indo-Pacific Ocean, you may be surprised to see a fantastic show, unlike anything you’ve seen before: the flashing of the clam Ctenoides ales, also known as the “disco” clam.
Since there are so many predators lurking in the beautiful waters of this ocean, the disco clam displays a somewhat stunning light show as part of its defense mechanism, and in so doing, it scares away any potential threats. But there’s another advantage that comes with this technique: the tiny mollusk also attracts its prey. These small clams are special due to the tiny shiny silica spheres in their lips which can reflect light and put on a shimmering underwater display.
This research was conducted by scientist Lindsey Dougherty, of the University of California, Berkeley, who first became mesmerized with disco clams during a trip in Indonesia. Dougherty explains that seeing the show during the dives was love at first sight and she has been planning to do a PhD on the disco clam ever since.
The experiments took place in an artificial environment (aquarium), where the disco clams were made to believe they are being attacked by predators, which turned out to be very realistic and scary for the clams. How could they know that? The clams’ flash rate increased from 1.5 times per second to 2.5 flashes per second when the “predator” was nearby. An interesting fact was that the flash rate of the clam jumps also when any possible prey, such as plankton, are in proximity.
In her experiments, Dougherty also found that the clam produces sulfuric acid, a process which could be a critical part of the clams’ defense strategy. In order to test this theory, Dougherty used calcium chloride, which reacts visibly in the presence of sulfuric acid. The researcher found that the levels of the resulted precipitate around the distressed clam were higher, rather than in the calm clam.
Studying the anatomy of the clams, Dougherty found that the clams have about 40 tiny eyes. However, their vision isn’t good enough to help them in their mating, since they are not able to detect the flashing of other disco clams.
Working with these clams in the wild, despite the visual appeal, also has its drawbacks. There are major differences between a lab experiment and an underwater experiment, due to the fact that even the simplest tests get exponentially more difficult.
Image Source: Discover Magazine