Amazing masters of disguise, octopuses can essentially vanish, right before your eyes, into a complex scene of colorful coral or a clump of kelp waving in the currents. How do these invertebrates manage this quick-change feat? Small pigment-filled cells, called chromatophores, and reflective ones, called iridophores and leucophores, in the skin of most octopuses allow them to create nuanced patterns of color and luminosity and even to harness polarized light to fool other ocean life. Scientists, however, have debated just what information they use to craft this overall effect. A paper published online in PLoS ONE suggests octopuses focus on a limited selection of nearby objects to determine their disguise, as opposed to incorporating the general hues and patterns of a whole area into their skin display.
The researchers, from Ben-Gurion University of the Negev in Israel and the Anton Dohrn Zoological Station Naples in Italy, studied digital underwater photographs of the common octopus (Octopus vulgaris) and the day octopus (O. cyanea) camouflaging in their natural habitats. They then ran those images through a computer program that picks out clusters of similar colors, lights and patterns. The almost invisible octopuses in the images most closely matched distinct landmarks such as corals or noticeable rocks.
The new paper does not, however, solve the debate about how these color-blind animals can create such a stunning, full-color display. The discovery of light-sensing proteins (opsins) in their skin suggests that they might be able to detect and react to color and light conditions locally. Yet so far only one hue of these cells has been discovered, so scientists are still searching for more clues about how these crazy cephalopods choose their wild disguises.
Adapted from the Octopus Chronicles blog at blogs.ScientificAmerican.com/octopus-chronicles