Cuttlefish, like other cephalopods such as octopuses and cuttlefish, are masters of disguise, changing skin color and texture to blend in with their underwater environment.
Now, in a study published on June 28, NatureResearchers at the Okinawa Institute of Science and Technology Graduate University (OIST) and the Max Planck Institute for Brain Research have shown that the way squid generate camouflage patterns is far more complex than previously thought.
Cuttlefish create their dazzling skin patterns by precisely controlling millions of tiny skin pigment cells called chromatophores. Each chromatophore is surrounded by a series of muscles that contract and relax under the direct control of neurons in the brain. When the muscle contracts, the pigment cells expand, and when the muscle relaxes, the pigment cells hide. Together, the chromophores act like pixels in cells to produce the overall skin pattern.
Professor Sam Reiter, who heads OIST’s Computational Neurobehavioral Unit, said, “Previous studies suggest that cuttlefish have a limited choice of pattern components that they use to achieve optimal adaptation to their environment. However, in our latest study, cuttlefish camouflage is much more complex and flexible in response, which we were unable to detect because previous approaches were not detailed or quantitative. bottom.”
To make this discovery, the researchers used a series of ultra-high-definition cameras to zoom in on the skin of a common European squid. Sepia Officinalis. Scientists gave the squid a variety of backgrounds. Cameras captured the expansion and contraction of tens to hundreds of thousands of chromatophores in real time as the squid moved between camouflage patterns.
Data from some 200,000 skin pattern images were processed by OIST’s supercomputers and analyzed by a form of artificial intelligence known as neural networks. Neural networks comprehensively explored various aspects of skin pattern images, including roughness, brightness, structure, shape, contrast, and more complex image features. Each pattern was then placed at a specific location in the ‘skin pattern space’. The term was coined by scientists to describe the full range of skin patterns produced by cuttlefish.
The researchers also used the same process to analyze images of the background environment to see how well the skin patterns matched the environment.
Overall, the researchers found that cuttlefish are capable of displaying a wide variety of skin patterns and are sensitive and flexible in changing skin patterns to both natural and artificial backgrounds. When the same animal was presented multiple times on the same background, the resulting skin patterns were subtly different, indistinguishable to the human eye.
The route taken by the squid to reach each skin pattern was indirect. Cuttlefish transitioned through different skin patterns, stopping along the way, with each pattern change improving camouflage until the squid stabilized on a satisfactory pattern. Such pathways are never the same even between two backgrounds of the same her, highlighting the complexity of squid behavior.
“The cuttlefish often paused past the target skin pattern and then came back,” says Theodosia-German, co-lead author of the study and a graduate student on the Max Planck Institute for Brain Research team. Mr Wu said. “In other words, rather than simply detecting the background and going straight to a set pattern, the squid may be continuously receiving feedback about its skin pattern and using that to adjust its camouflage. Exactly how they receive that feedback – whether they’re using their eyes or sensing how much the muscles around each chromatophore are contracting – remains to be seen. yeah.”
The researchers also looked at the display of another skin pattern, called chlorosis, that occurs when cuttlefish turn pale in response to threat. “Unlike camouflage, blanching is rapid and direct, suggesting it uses another reproducible control system,” said Dr. Dominique Evans, a postdoctoral fellow on the Max Planck Brain Institute team. There are,” he said.
When the researchers took high-resolution images of the branching display, they found that some elements of the previous camouflage pattern remained, with the branching pattern superimposed on top. The cuttlefish then slowly but surely reverts to its pre-blanching skin pattern.
“This suggests that some form of information about the initial camouflage remains. They may be controlled by different neural circuits,” explained co-investigator Dr. Xitong Liang. First author of the study and former postdoctoral fellow of the Max Planck Institute for Brain Research team. “The next step is to capture neural recordings from the squid’s brain, which will allow us to better understand how the squid controls its unique and fascinating skin patterning abilities.”
