Sophisticated Symbiosis

Specialized giant clam cells distribute photosynthetically productive light to symbiotic microalgae in an energy-efficient manner.

Oct 8, 2014
Tracy Vence

WIKIMEDIA, JANDERKIridescent cells in the mantle tissue of giant clams spread light of a wavelength that drives photosynthesis  to microalgae that provide nutrition for the animals, the University of Pennsylvania’s Alison Sweeney and colleagues reported in Journal of the Royal Society Interface this month (October 1). These so-called iridocytes not only distribute photosynthetically productive light to the algae, they also reflect nonproductive light, the researchers showed. “At incident light levels found on shallow coral reefs, this arrangement may allow algae within the clam system to both efficiently use all incident solar energy and avoid the photodamage and efficiency losses,” the researchers wrote in their paper.

“What makes this system in the clam special is that the design can extract every last photon from sunlight,” Sweeney told New Scientist.

“While earlier work speculated on the role of these iridescent cells, this paper clearly shows how clams use iridocytes to control and redistribute the light that reaches their algal symbionts,” added Ryan Kerney of Gettysburg College in Pennsylvania who was not involved in the work.

In their paper, the researchers likened the symbiotic system to an electric transformer, “which changes energy flux per area in a system while conserving total energy.” Given this parallel, the authors proposed that the clam system might inspire the development of more efficient and resilient photovoltaic materials.