See how giant clams help their symbiotic partner

Like corals, giant clams are important participants in reef ecosystems and live in symbiosis with

photosynthetic algae Symbiodiniaceae.Shellfish also have specialized cells known as iridocytes that can manipulate light through layers of nanoreflectors in each cell. Earlier work showed that these iridocytes scatter and reflect light to increase the photosynthetic efficiency of the Symbiodiniaceae algae.

Now a team of scientists from the Researchthe Red Sea Center and the Photonics Laboratory discovered another way that iridocytes help the symbiont photosynthesize. Experts studied the morphology and optical characteristics of iridocytes at the maxima of the giant mollusk Tridacna. As a result, scientists found that they absorb ultraviolet radiation, and in addition, re-emit it in the form of photosynthetically useful light with a longer wavelength.

A different slant of light from KAUST Discovery on Vimeo.

Ram Chandra Subedi, one of the authors of the study,explains that iridocytes contain alternating layers of a high refractive index guanine crystal and a low refractive index cytoplasm. The compression and relaxation of these layers allows the cell to adjust its effect on the light. As a result, guanine palettes not only reflect harmful ultraviolet radiation, but also absorb it and emit light at higher wavelengths, which are safe and useful for photosynthesis.

This increases the amount of photosynthetically active radiation available to the algal symbiont and also helps protect the shellfish and algae from ultraviolet radiation.

Additionally, this process can explain the colorsmantles of giant clams. Their bright colors are not due to optical differences in the tissue, but to differences in the distribution or number of symbionts relative to iridocytes in each individual.

Scientists warn that this is justa hypothesis, but, in their opinion, the most reasonable explanation for the different color of mollusks. Whether color differences are functional implications remains an open question.

Researchers say the project itself was originally based on curiosity. Scientists wanted to see if iridocytes have optical properties that can be useful in photon technology.

Initially it wasn't about answering a biology question, but it ended up explaining a lot about this symbiosis and opening up new questions in the field of biological photonics.

Suzanne Rossbach, lead author of the study

Read also

Germany became the first major economy to abandon coal and nuclear power

It turned out that made the Mayan civilization leave their cities

Look at the bare core of a giant planet: scientists have found this for the first time