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>This is no small feat given the complexity of backgrounds in marine environments (such as those found on coral reefs). What's more, an octopus must carefully orchestrate 10 million to 20 million chromatophore organs in its skin as well as another million or so iridescent cells and perhaps several thousand skin bumps (called papillae) to tailor its camouflage pattern to every specific microhabitat it stops in while foraging. Of course, if you can change your appearance, you have to control it, and that requires good vision and a large brain to process the visual information, send signals to all those skin elements and get the pattern deployed.
>How cephalopods managed this evolution is more difficult to uncover. A basic flaw in biological thought during the past century is the idea that camouflage is "looking like the background." In retrospect, this does not make much sense simply because there are too many backgrounds. A typical Caribbean coral reef, for example, has 600 to 1,000 species on it (e.g., corals, bryozoans, tunicates, algae, seagrasses, etc.), so trying to resemble that many backgrounds is a senseless idea. A better approach is to study the animal group that changes its camouflage dynamically throughout these complex backgrounds (cephalopods) and determine how many patterns it needs and what sorts of tricks it has evolved to deceive multiple visual predators. One sage put it thus: "Camouflage is the least-studied biological subject that we think we already know about." Fortunately, that is changing.
>The elegance of the three-pattern system is that it helps explain how the cephalopods can change so fast. The most parsimonious explanation is that they need to see only one visual cue in the background to turn on a disruptive pattern and another to turn on mottle; uniform could be a default pattern. If the cephalopod instead analyzed all the visual information from surrounding corals, it would need a super computer to analyze that amount of information — and that would take time as well. Since the animals make these magical transformations in less than a second, the single-cue explanation is probably on the right track.
>In addition, only cephalopods have evolved the unique ability to morph their skin into various grades of bumpiness with well-controlled skin papillae, which can range from flat and invisible (i.e., smooth) to spiky in many degrees to match the 3-D rugosity of the substrate. This helps to obscure the outline of the animal too, since if its skin were smooth its outline would stand out against nonsmooth backgrounds such as coral polyps or hydrozoan-populated seagrass fronds.
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>It is better to find the animal's den and watch it for long periods until the animal emerges to forage. The octopus can then be habituated to diver presence so that it will forage, and the diver can follow it at a discrete distance to watch the amazing sequences of camouflage on different backgrounds. This approach requires immense patience though. Volunteer divers have greatly facilitated such studies and contributed to substantial biological discoveries.
>An amazing and serendipitous discovery did emanate from this conundrum: it turns out the skin has the same light-detecting molecules as those found in cephalopods' retinas. So, hypothetically, the skin can somehow sense light and perhaps even color. Currently this idea is a bit of a pipe dream, but this is the way scientific inquiry proceeds — an unusual discovery transforms the way a problem is probed.
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![]() >arms parted in a V and displays longitudinal stripes similar to the coral. |
>New cameras called hyperspectral imagers (HSI) are being developed to acquire color-rich images so that it is possible in postprocessing to tune the resulting photograph to the color gamut of different predators with different color-viewing capabilities. This will elevate the ecological study of visual predator-prey interactions and help quantify the color aspects of camouflage in realistic scenarios. Don't be surprised if scientists demonstrate that an octopus camouflaged to you is not as well color-camouflaged to a barracuda. Such studies are difficult, yet advancing technology can open the door to new approaches such as this.
>The diving world is a goldmine of color and pattern diversity. Charismatic species such as cephalopods, which are the masters of color change on planet Earth, are fun to watch though sometimes challenging to find and study. Their camouflage is highly sophisticated, and those who witness it are usually in awe. So sharpen your eyes, and good hunting.
>NOTE: These photos of camouflaged animals were taken using available light; the use of strobe lighting could potentially alter their behavior and our perception of their color.
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>© Alert Diver — Q4 Fall 2017