WASHINGTON – Cuttlefish are ugly-cute. With their big eyes, stubby tentacles and bulbous head, they look like creatures from an H.P. Lovecraft horror story. When they move forward, rippling their fins underneath their body, they resemble prehistoric flying saucers. And they hunt at night and are masters of disguise.
This last attribute, it turns out, may have value beyond the sea. New research is starting to show that cuttlefish and their squid cousins may hold the key to the creation of new kinds of camouflage to mask clothes, vehicles and even buildings.
Unlike any other animal, 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 enable them to change color without sending messages to the brain. Exactly how this works is still a mystery.
Roger Hanlon, a senior scientist at the Marine Biological Laboratory in Woods Hole, Massachusetts, is collaborating with bioengineers across the U.S. to develop a material that mimics this camouflage mechanism.
The material might be able to hide objects or change the tint of a car. It could even keep buildings cool in the summer and warm in the winter by darkening their exteriors to absorb heat and lightening them to reflect it.
In 2010, Hanlon and Lydia Mathger, a fellow researcher at his lab, published a study showing that the same gene that produces light-sensing molecules in the retina is distributed throughout the skin of cuttlefish.
The finding was a huge 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 discovered this gene, for a protein called opsin, concentrated near chromatophores — tiny organs that consist of an elastic sac of red, yellow or black pigment tied to muscle fibers.
The scientists believe that the protein senses light and the chromatophores alter skin color. Opsin may be acting on its own without brain signals and may be somehow connected to the chromatophores.
Mathger thinks the presence of opsin may mean that the otherwise colorblind cuttlefish can “see” a multicolored environment through their 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 relative of the cuttlefish: 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.”
While Cronin and Kingston probe the inner workings of squid skin, engineers funded by the Virginia-based Office of Naval Research are trying to make a similar camouflage material out of silicon and circuits. This artificial skin might help the Pentagon make its tanks and submarines disappear, for instance, or turn a wall into a 3-D TV camera, according to Richard Baraniuk, a professor of electrical engineering at Rice University and a collaborator on the project.
“What we are designing is a passive system that interacts with the ambient light, channels the right amount to the right direction so you can camouflage yourself,” Baraniuk said. “It’s not like any kind of imaging device that has ever been designed.”
By harnessing the light-gathering and color-shifting abilities of cuttlefish and other undersea animals, Baraniuk and other bioengineers dream of building a thin electronic “skin” able to turn an entire room into a camera, surreptitiously transmitting images of what’s happening inside. That may seem a bit creepy, but the technology could also be used to design new kinds of 3-D televisions, holographic games and medical imaging devices.
“Just imagine surfaces that would be wallpapered that turn into a camera,” said John Rogers, a professor of materials science at the University of Illinois, Champaign-Urbana, who is also exploring this concept.
The initial prototype will be a black-and-white version that can match its surroundings, Rogers said. Flexible camouflage panels will contain sacs of colored dyes that contract or expand, just like the skin of a cuttlefish or squid.
But experts say a stack of engineering problems must still be solved before clothing that changes color to match its background hits store shelves. That’s because there are still a lot of factors scientists don’t understand about how cuttlefish skin changes color.
This ability to change color is the result of a cascade of events influenced by chemical and physical signals from the surroundings, the animal’s own chemical hormones and electrical impulses from the brain, according to Andrea Toa, an assistant professor of nano-engineering at the University of California, San Diego. She says that fabricating a similar cascade won’t be easy.
“Squid have very complex systems,” said Toa, who is not involved in the Office of Naval Research project. “In a camouflage device, you have man-made elements which boil down to an electrical circuit.”
Yet researchers including Baraniuk and Rogers point to other advanced devices as evidence that nature and engineering can work together. Scientists in Japan are building “krill-eye,” a wide-angle lens that collects light in the way a shrimp’s compound eye does, while an Oregon lab is designing “neuromorphic” computer chips that mimic the way the brain’s neurons work — sending messages in spikes of energy instead of a continuous current.
“Whatever we learn from this,” Baraniuk said, “will be applicable way beyond mimicking camouflage.”