A new study finds how squids control their light-reflecting property and change their skin color that help them to camouflage.
A team of researchers led by Paloma Gonzalez Bellido and Trevor Wardill from the Marine Biological Laboratory (MBL) probed into the iridophore control mechanism of the longfin inshore squid (Doryteuthis pealeii). Squids have pigment-producing cells known as chromatophores. Yellow, red and brown chromatophores surround one iridophore, which consists of hundreds of iridescence cells.
Iridophore reflects light and changes the skin color. Squids also use this property to escape and hide themselves from deep-ocean predator attacks. They are capable of responding to light illuminated by predators to find their prey.
When a light falls on the squids, they immediately change their color from transparent to pigmented. Besides, squids also use their light-reflecting property to communicate with other members of the species.
While squids' light-reflecting property is already known, what causes the change in skin color was something that was not learnt.
For their study, experts stimulated a group of nerves electrically and found that the nerves caused the change in skin color of the squids from red and orange to yellow, blue and green at a rapid speed. They revealed that the squids were able to change their color in just 15 seconds.
"For 20 years we have been wondering how the dynamically changeable iridescence is controlled by the squid," study co-author Roger Hanlon, said in a statement from MBL.
"At long last we have clean evidence that there are dedicated nerve fibers that turn on and tune the color and brightness of iridophores. It is not an exaggeration to call this "electric skin." The complex nerve network distributed throughout the squid's skin instantly coordinates tens of thousands of chromatophores with iridescent reflectors for rapidly changing behaviors ranging from camouflage to signaling," he said.
Researchers also studied how squids are able to change their color as they are completely colorblind. One possibility suggested is that squids change color from red to blue to increase the brightness of iridophores. "This is because squid see predominantly blue light. Blue light is especially important in the ocean as it penetrates best into deeper water," said Wardill.
The findings of the study are published in the journal Biological Sciences.