Reflective Platelets in Squid Are Composed of Protein

The Hawaiian bobtail squid Euprymna scolopes camouflages itself using reflective tissue composed of flat, structural platelets of high refractive index. In the Jan. 9 issue of Science, researchers at the University of Hawaii at Manoa in Honolulu and at the University of California, Los Angeles, report that the squid's platelets are based on proteins, which they have dubbed "reflectins," rather than on the purine crystals typical of the reflective tissue in other aquatic animals.

The proteins are composed of relatively rare amino acids -- tyrosine, methionine, arginine and tryptophan -- and lack some of the more common ones. Because the reflectins have not been found outside of the squid family, the researchers say that they are a good example of the natural nanofabrication of photonic structures.

A distant goal of the research is to couple the proteins with artificial photosynthetic membranes or similar molecular light-producing systems, where reflectors might increase efficiency.