Several articles appeared yesterday about how a small Hawaiian squid is using reflective plates to confuse predators, paving the way for a new generation of optical nanotechnology tools. Here are two short stories from Scientific American, "Squid May Inspire New Nanolights," and from Ananova, "Nature's 'searchlight' could leave inventors squids in."
Before going further, here is an image of this three-inch-long Hawaiian bobtail squid Euprymna scolopes (Credit: Ronald R. Holcom).
Scientific American says that this small squid has "a built-in flashlight made up of a previously unknown type of protein." The authors of the study called it "reflectin".
Wendy J. Crookes of the University of Hawaii-Manoa and her colleagues studied the three-inch-long squid Euprymna scolopes, commonly called the Hawaiian bobtail squid. The animal has a light-producing organ on its underside that helps it feed in dark waters and may help provide camouflage from predators. Glowing bacteria provide the light source, which is surrounded by stacks of reflective plates.
But unlike previously studied reflective plates in other aquatic animals -- the majority of which are made up of crystals of a chemical known as purine -- the squid’s reflective tissue is protein-based. The group of proteins, dubbed reflectins by the authors, has an unusual amino acid composition. The team notes that the reflectins are "a marked example of natural nanofabrication of photonic structures" and should inspire bottom-up synthesis of new spectroscopic and optic devices.
This report was published yesterday by Science. Here is the abstract of this report, "Reflectins: The Unusual Proteins of Squid Reflective Tissues," authored by Wendy J. Crookes, Lin-Lin Ding, Qing Ling Huang, Jennifer R. Kimbell, Joseph Horwitz, and Margaret J. McFall-Ngai (Free registration needed).
A family of unusual proteins is deposited in flat, structural platelets in reflective tissues of the squid Euprymna scolopes. These proteins, which we have named reflectins, are encoded by at least six genes in three subfamilies and have no reported homologs outside of squids. Reflectins possess five repeating domains, which are highly conserved among members of the family. The proteins have a very unusual composition, with four relatively rare residues (tyrosine, methionine, arginine, and tryptophan) comprising 57% of a reflectin, and several common residues (alanine, isoleucine, leucine, and lysine) occurring in none of the family members. These protein-based reflectors in squids provide a marked example of nanofabrication in animal systems.
I'm not sure if this will lead to future nanolight tools, but Ananova reports that "the structure of the reflecting plates could offer inspiration to nanotechnology designers."
Sources: Sarah Graham, Scientific American, January 9, 2004; Ananova, January 9, 2004; Science, Volume 303, Number 5655, January 9, 2004