Nerve cells—dyed red in the above image—are responsible for squids' shimmering displays of iridescence, new research shows.
A squid's shifting metallic sheen comes from clusters of tiny platelike structures inside their skin cells. (See squid pictures.)
Known as iridophores, the microscopic ensemble interferes with the way certain wavelengths of light are reflected.
"It's the same effect you get with shiny colors on a soap bubble or a thin layer of oil on the water surface in a harbor," said study co-author Paloma Gonzalez-Bellido, a neuroethologist at the Marine Biological Laboratory in Woods Hole, Massachusetts.
Exactly how squid turn these iridophores on and off has, until now, remained a mystery.
A new technique allowed the team to hook up electrodes to individual nerves in squid skin. When they sent electrical impulses into the nerves, the iridophores changed color and brightness.