Unlike any other animals, cuttlefish and squid use light to blend into or stand out from their surroundings. Marine scientists believe they do this using tiny sensors all over their skin that help them change color without sending messages to the brain. Exactly how it works is still a mystery.
Roger Hanlon, a senior scientist at the Marine Biological Laboratory in Woods Hole, Mass., is collaborating with bioengineers across the country to develop a material that mimics this camouflage mechanism. The material might be able to hide objects or change the tint of your car. It might even allow buildings to keep cool in the summer and warm in the winter by darkening to absorb heat and lightening to reflect it.
‘Why does it need that?’
In 2010 Hanlon and Lydia Mathger, a researcher in his lab, published a study showing that the same gene that produces light-sensing molecules in the retina was distributed throughout the skin of cuttlefish. The finding was a big surprise.
“When we started, we thought: What on earth is this doing in the skin?” Mathger said. “It’s the same visual pigment as in the eye. Why does it need that?”
The researchers found this gene (for a protein called opsin) concentrated near chromatophores; these tiny organs consist of an elastic sac of red, yellow or black pigment and are tied to muscle fibers. The scientists believe that the protein senses light while the chromatophores change the skin color. The opsin may be acting on its own without brain signaling and may be somehow connected to the chromatophores. Mathger believes the presence of opsin may mean that the otherwise colorblind cuttlefish can “see” a multicolored environment through its skin. But Hanlon and other scientists at Woods Hole and elsewhere are still trying to prove the connection.
Alexandra Kingston, a biology graduate student at the University of Maryland Baltimore County, is exploring the role of opsin in a cuttlefish relative, the long-finned squid. Kingston has found the protein all over the squid’s skin, and she is now looking for retinochrome, another protein that switches opsin on and off.
“It’s a recycling mechanism for the opsin,” Kingston said. “We have the opsin molecules, but do they have the [light-sensing] cells? That’s what we are working on right now.”
Kingston’s adviser, Tom Cronin, says that more sea creatures that use camouflage — such as the flounder and the mantis shrimp — are being found to have light-sensing opsin on their skin.
“Light sensing has lots of different jobs besides vision,” said Cronin, who is collaborating with Hanlon. “It will tell you whether it’s day or night, how shallow you are, how deep you are. It may not be related to camouflage. But what’s surprising is, they use the exact same protein that is in their eye.”