For this latest study, Dougherty and her team conducted fieldwork at Lizard Island Research Station in Australia and the Raja Ampat Research and Conservation Center and Lembeh Resort in Indonesia. The researchers used a bunch of high-tech methods - transmission electron microscopy, spectrometry, high speed video, energy dispersive x-ray spectroscopy and computer modeling - to study the detailed internal structure of the margin of the clam's lip. That's where the light show happens.
The inside of the clam's lip is packed with tiny spheres of silica, the primary component of glass. These spheres are only 340 nanometers in diameter, and they are ideal reflectors, particularly of the blue light that penetrates deeper into seawater than red light. The outside of the lip contains no silica nanospheres. As a result, when the clam lip is furled, no light is reflected.
This turns out to be the secret behind the light show. Previously it was thought that the flashing was due to bioluminescence, a chemical reaction. Other marine organisms, such as lantern sharks, use bioluminescence.
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In this case, when the clam unfurls its lip - typically twice a second - the millimeter-wide mirror is revealed and reflects the ambient light, like a disco ball.
Now the question is: Why? Dougherty and her team are now exploring whether the clam is trying to attract prey (mostly plankton) or other clams and potential breeding partners - or if it is trying to scare away predators.
As part of that process, the researchers are examining the clam's eyes - all 40 of them - to determine if the clam can even view its own impressive light shows.
Photo: Lindsey Dougherty, UC Berkeley