Even though most creatures use any of a variety of types of camouflage, scientists know very little about the way effective camouflage is created and its characteristics. Cephalopods – the molluscan class that includes octopuses – are considered the most developed, from an evolutionary point of view, of any sea creatures.
It is known that their flexible nervous system allows the cephalopods to change the color and even the texture of their skin to adapt to their environment. The existence of large numbers of sea predators is the driving force for the development of various defensive mechanisms and behaviors, including camouflage. The best way to avoid becoming lunch is to make sure that nobody else sees you.
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But the cephalopods, which may look like they have a low IQ, are even cleverer, according to findings by Ben-Gurion University doctoral student Noam Josef, supervised by Dr. Nadav Shashar. He recently published an article on the subject in the journal PLoS One that aroused much interest among scientists. The BGU team did their research at the Eilat campus for marine biology and biotechnology research, along with colleagues at the Naples Zoological Station, creating mathematical tools to analyze photographs, the environmental parameters and the amount of information collected to create a believable disguise.
The Israelis flew to the island of Capri to photograph two local specimens – Octopus cyanea and Octopus vulgaris – with their Italian colleagues. Each of the images was taken from above, as if it were viewed from the level of a shark, and in gray tones (because octopuses are color blind.) From the photos, they chose a white rectangle containing the cephalopod’s “head” without the eight legs. A computer program compared that section to other parts of the picture, looking for similar images.
The most similar textures and shades on the octopus’s head did not appear on the seabed near the octopus.
Instead, 10 of 11 of the creatures adapted themselves to objects lying on the seabed such as corals, rocks, odd bits of colored sand and algae spots.
An octopus that sits on coral has to be camouflaged to avoid large fish swimming above, as well as eels and other predators that attack from the sides, the team said.
Since enemies attack from different angles, they will view the octopus against different backgrounds. Thus it is “logical,” they continued, that the creature does not try to produce perfect camouflage on its skin. Even after it “dresses” to “disappear,” sometimes they “err” and remain partially visible. The environment of coral reefs is so complex that just adopting the main characteristics of the objects can serve the octopus better than becoming absolutely invisible, they said. The marine researchers discovered special pigment cells in the octopus skin that helps them create camouflage. Some cells reflect light while others disperse it.
But the team said that more questions than answers remain. “What are the visual hints that these living creatures use? How do octopuses suit their colors even though they are color blind? What data is transmitted from the eye to the brain? And what does the octopus really see? We are still far from completely understanding the principles of [natural] camouflage. We must continue to search for pieces of information, if we can find them at all.”