Seeing through squids’ camouflage

Squids can tune the brightness and color of their reflected light for camouflage and communication thanks to a protein called reflectin. Previous studies on the protein have led researchers to attribute the special cloaking ability of squids almost entirely to the unique structure and behavior of reflectin. However, none of the fabricated thin films or recombinant cells using reflectin were able to produce a signal-activated increase in the reflectance intensity as strong as those found on squids.

Daniel Morse and Esther Taxon offer an alternative perspective that emphasizes the importance of an amplifier for reflectin. In the perspective, they present recent research pertaining to relevant molecular mechanisms responsible for enhancing the reflectance intensity. They explain how, in squids, the reflectin’s osmotic control of the membrane-bound nanostructures, which work as Bragg reflectors or Mie scatterers, amplifies the intensity of the reflected light.

“We show, for the first time, the role and requirement for a closely coupled amplifier needed for tuning the intensity as well as the color of reflected light,” Morse said. “Not intended by any means as a criticism of previous work, our perspective simply points to a key area of future research and development.”

The authors suggest that future research on thin films and cells could realize amplification similar to the squid system by incorporating reflectin in semi-permeable membrane-based structures.

Morse said that understanding underlying mechanisms of color tunability in squids and other animals boasts future applications beyond biological systems. “We anticipate the development of synthetic, reflectin-inspired signal responsive polymeric materials and membrane-inspired, plasmonic, tunable amplifiers of photonic behavior,” he said.

Source: “Reflectin needs its intensity amplifier: Realizing the potential of tunable structural biophotonics,” by Daniel E. Morse and Esther Taxon, Applied Physics Letters (2020). The article can be accessed at https://doi.org/10.1063/5.0026546 .