Scientists from the Max Planck Institute for Brain Research and the Okinawa Institute of Science and Technology studied camouflage in the common cuttlefish (Sepia officinalis) — a master of camouflage — as behavior moves toward matching the background in skin pattern space. Their observations suggest that the cuttlefish’s camouflage system is highly flexible and adaptable, providing new insights into this complex physiological process.
“Cephalopod camouflage consists of matching the animal’s appearance to its substrate and typically contains 2D and 3D components,” said senior author Dr. Gilles Laurent from the Max Planck Institute for Brain Research and colleagues.
“Although both components are technically textural in this field, the term ‘texture’ is often applied only to 3D features, caused, for example, by the contraction of skin papillae.”
“We studied the 2D features of the camouflage and therefore referred to them as skin patterns and in the process as pattern matching,” they added.
“Pattern matching does not consist of a faithful reproduction of the appearance of the substrate but, rather, of visually initiated statistical estimation and generation of that appearance.”
“These sophisticated operations were carried out naturally by the brains of animals that diverged from us more than 550 million years ago, before large brains existed.”
“The formation of 2D skin patterns relies on a motor system that controls the expansion state of up to several million pigment cells (chromatophores) embedded in the animal’s skin, among other specialized types of the cell.”
“The state of expansion of each chromatophore depends on a radial array of muscles that control the size of a central pigment sac and, therefore, the activity of one to several motoneurons, the dendrites and somata present in the central brain of the animal. “
“Skin pattern formation therefore results from the appropriate coordination and control of tens of thousands of motoneurons of a system that interprets complex visual scenes.”
In their research, the authors studied the camouflage behavior of the common cuttlefish on natural and artificial backgrounds, gathering more than 200,000 images that were used to map the color change process in a single-cell resolution.
Data from these maps indicated that each pattern was highly detailed and that the same background could yield many different results.
These camouflage pathways were found to involve a continuous feedback mechanism and the final camouflage was the product of successive error correction steps, indicating that the process is highly adaptive and not following a set path each time.
The exception to this rule is during blanching, a defense mechanism in which cephalopods turn pale in response to threatening stimuli.
This process was observed to be rapid and direct, and the memory preserved by the initial masking was revealed again as soon as the threat was withdrawn.
The team’s results provide important insight into the way these immune mechanisms interact with each other, and how the complex process of color matching is achieved at a cellular level.
“Unlike camouflaging, blanching is rapid and direct, suggesting that it uses a different and repeatable control system,” said co-author Dr. Dominic Evans, a postdoctoral fellow at the Max Planck Institute for Brain Research.
“Cuttlefish often overshoot their target skin pattern, stop, and then come back,” said first author Theodosia Woo, a graduate student at the Max Planck Institute for Brain Research.
“In other words, cuttlefish don’t just see the background and go straight to a set pattern, instead, they probably continuously receive feedback about the pattern of their skin 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 much the muscles around each chromatophore contract – we don’t know yet.”
The study was published in the journal Nature.
Q. Woo et al. The dynamics of pattern matching in camouflaging cuttlefish. Nature, published online June 28, 2023; doi: 10.1038/s41586-023-06259-2
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