Cuttlefish camouflage is even more intricate and flexible than previously thought, according to new research published in Nature.
The charismatic cephalopods carefully match their skin pattern to their background environment by precisely controlling millions of individual tiny skin pigment cells, called chromatophores.
These cephalopods match their skin to both the two-dimensional and three-dimensional components of the background, adjusting for colour, roughness, brightness, structure, shape and contrast.
Using ultra-high-resolution cameras to capture the common European cuttlefish, Sepia officinalis, as it transitioned between colours, patterns, brightness and shape in real time, researchers from the Okinawa Institute of Science and Technology and the Max Planck Institute for Brain Research were able to zoom in on the expansion and contraction of these chromatophores.
Cuttlefish were placed into tanks (70 x 70 x 13.5 cm), with different background images mounted behind them in random order.
Researchers then used artificial intelligence to analyse around 200,000 images of the cuttlefish skin (for roughness, brightness, structure, shape and contrast) as well as the background environment.
The results show the expansive spectrum of individual skin cell patterns work together like pixels to generate the overall camouflage. Each camouflage pattern is uniquely matched to the environment and highly dimensional.
By capturing the process on camera, the researchers were able to see how 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.
The results help explain how cuttlefish are able to display such a rich variety of skin patterns, which they can sensitively and flexibly change to match both natural and artificial backgrounds.
“The cuttlefish would often overshoot their target skin pattern, pause, and then come back,” said Theodosia Woo, lead author based at the Max Planck Institute.
“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.”
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