MSGID: 1:317/3 649d08eb   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Cuttlefish camouflage: More than meets the eye    
    High resolution video coupled with artificial intelligence reveals that   
   camouflaging in cuttlefish is more complex than previously thought    
      
     Date:   
         June 28, 2023   
     Source:   
         Okinawa Institute of Science and Technology (OIST) Graduate   
         University   
     Summary:   
         Researchers have shown that the way cuttlefish generate their   
         camouflage pattern is much more complex than previously believed.   
      
      
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   Cuttlefish, along with other cephalopods like octopus and squid, are   
   masters of disguise, changing their skin color and texture to blend in   
   with their underwater surroundings.   
      
   Now, in a study published 28 June inNature, researchers at the Okinawa   
   Institute of Science and Technology (OIST) and the Max Planck Institute   
   for Brain Research have shown that the way cuttlefish generate their   
   camouflage pattern is much more complex than previously believed.   
      
   Cuttlefish create their dazzling skin patterns by precisely controlling   
   millions of tiny skin pigment cells, called chromatophores. Each   
   chromatophore is surrounded by a set of muscles, which contract and relax   
   under direct control of neurons in the brain. When the muscles contract,   
   the pigment cell is expanded and when they relax, the pigment cell is   
   hidden. Together, the chromatophores act like cellular pixels to generate   
   the overall skin pattern.   
      
   Professor Sam Reiter, who leads the Computational Neuroethology Unit at   
   OIST said: "Prior research suggested that cuttlefish only had a limited   
   selection of pattern components that they would use to achieve the best   
   match against the environment. But our latest research has shown that   
   their camouflaging response is much more complicated and flexible --   
   we just hadn't been able to detect it as previous approaches were not   
   as detailed or quantitative."  To make their discovery, the team used   
   an array of ultra high-resolution cameras to zoom into the skin of the   
   common European cuttlefish, Sepia officinalis. The scientists presented   
   the cuttlefish with a range of different backgrounds. As the cuttlefish   
   transitioned between camouflage patterns, the cameras captured the   
   real-time expansion and contraction of tens to hundreds of thousands   
   of chromatophores.   
      
   Data from around 200,000 skin pattern images were then crunched by the   
   supercomputer at OIST and analyzed by a type of artificial intelligence,   
   known as a neural network. The neural network looked holistically   
   at the different elements of the skin pattern images, including   
   roughness, brightness, structure, shape, contrast, and more complex   
   image features. Each pattern was then placed into a specific location in   
   'skin pattern space', a term the scientists coined to describe the full   
   spectrum of skin patterns generated by the cuttlefish.   
      
   The researchers also used the same process to analyze images of the   
   background environment, and looked at how well the skin patterns matched   
   the environment.   
      
   Overall, the researchers found that the cuttlefish were able to   
   display a rich variety of skin patterns and could sensitively and   
   flexibly change their skin pattern to match both natural and artificial   
   backgrounds. When the same animal was presented with the same background   
   multiple times, the resulting skin patterns subtly differed in ways that   
   were indistinguishable to the human eye.   
      
   The path that the cuttlefish took to reach each skin pattern was   
   indirect. The cuttlefish transitioned through a range of different   
   skin patterns, pausing in between, with each pattern change improving   
   the camouflage until the cuttlefish stabilized on a pattern they seemed   
   satisfied with. Such paths, even between the same two backgrounds, were   
   never the same, emphasizing the complexity of the cuttlefish's behavior.   
      
   "The cuttlefish would often overshoot their target skin pattern,   
   pause, and then come back," said Theodosia Woo, joint first author of   
   the study and graduate student in the Max Planck Institute for Brain   
   Research team. "In other words, cuttlefish don't simply detect the   
   background and go straight to a set pattern, instead, it is likely   
   that they continuously receive feedback about their skin pattern   
   and use it to adjust their camouflage. Exactly how they receive that   
   feedback -- whether they use their eyes, or whether they have a sense   
   of how contracted the muscles around each chromatophore are -- we don't   
   yet know."  The researchers also examined another skin pattern display,   
   called blanching, which occurs when cuttlefish turn pale in response to a   
   threat. "Unlike camouflaging, blanching was fast and direct, suggesting it   
   uses a different and repeatable control system," said Dr. Dominic Evans,   
   a postdoctoral fellow in the Max Planck Institute for Brain Research team.   
      
   When the researchers took high resolution images of the blanching display,   
   they realized that some elements of the previous camouflage pattern   
   remained, with the blanching pattern superimposed on top. Afterwards,   
   the cuttlefish would slowly but reliably return to displaying its   
   pre-blanching skin pattern.   
      
   "This suggests that information about the initial camouflage somehow   
   remains.   
      
   The blanching is more like a response that temporarily overrides the   
   camouflage signals from the brain and might be controlled by a completely   
   different neural circuit in the brain," explained Dr. Xitong Liang,   
   joint first author of the study and former postdoctoral researcher in   
   the Max Planck Institute for Brain Research team. "The next step is   
   to capture neural recordings from cuttlefish brains, so we can further   
   understand exactly how they control their unique and fascinating skin   
   patterning abilities."   
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       * RELATED_TERMS   
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             o Hazardous_waste o Adult_stem_cell   
      
   ==========================================================================   
   Story Source: Materials provided by   
   Okinawa_Institute_of_Science_and_Technology_(OIST)   
   Graduate_University. Note: Content may be edited for style and length.   
      
      
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   Journal Reference:   
      1. Theodosia Woo, Xitong Liang, Dominic A. Evans, Olivier Fernandez,   
         Friedrich Kretschmer, Sam Reiter, Gilles Laurent. The dynamics of   
         pattern matching in camouflaging cuttlefish. Nature, 2023; DOI:   
         10.1038/s41586- 023-06259-2   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/06/230628130352.htm   
      
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