Proteins Help Squid Cast Beam

Scientists have found an odd, light-reflecting protein in the body of a squid that could one day prove useful in the design of microscopic optic devices.

The discovery, reported in the current issue of Science, was made by researchers at the University of Hawaii and UCLA investigating the light-emitting organ of Euprymna scolopes, the Hawaiian bobtail squid.

The organ casts a beam of light to camouflage the squid from predators lurking below; it consists of a lens, a cluster of luminescent bacteria and many tiny reflective platelets to direct the beam of light downward. The nature of the reflective material had been a mystery.

The team identified several closely related proteins that were abundant in the organ’s reflective platelets, as well as in reflective tissues elsewhere in the squid. The proteins, christened “reflectins,” differ from reflective platelets in fish, which consist of chemicals called purines, said first author Wendy Crookes, a researcher in Hawaii.

The squid can increase or decrease the platelets’ reflective ability, possibly by altering the structure of reflectins, Crookes said.