As the Hawaiian bobtail squid glides through the ocean on moonlit nights, when darkness alone wouldn't cloak it, reflective materials in its tissues render the animal invisible. Biologists have long known that squid and other cephalopods such as octopuses manipulate light in this way.
"But nobody could figure out what the agent was that was helping these animals become reflective," says Wendy Crookes at the University of Hawaii at Manoa.
Now, she and her colleagues have uncovered the squid's secret. Embedded in the animal's reflective tissues is a unique set of proteins that the researchers call reflectins.
In earlier studies, scientists led by Margaret McFall-Ngai at the same