Questions 46-50 Almost all cephalopods — the class of ocean dwellers that includes octopuses, cuttlefish, and squids — have an incredible ability not just to change the color and patterns on their skin, but also to transform their body’s shape and texture. Thanks to these tricks, cephalopods can radically change their appearance faster than the blink of an eye, the swiftest known change in the animal kingdom. This group of soft-bodied mollusks have skin covered in millions of pixel-like cells called chromatophores: pigment-filled sacs each surrounded by their own small muscle fiber. These muscles can stretch the chromatophore to flood with color or contract and shrink to a dot, creating varied, complex patterns. Octopuses and cuttlefish are also covered in small bumps, flaps, branches, and ridges called papillae, which can be ruffled upwards or smoothed out to create different skin textures too. The common day octopus can become almost see-through beige and white on flat sandy surfaces; dark, mottled, and rugged on bumpy rocks; and flashes orange, red, and brown spikes along corals. Cuttlefish sometimes clump up, shrivel, and hide their arms to look like a tuft of algae, and baby giant cuttlefish (Sepia apama) hiding among seaweeds have been recorded sending waves of shaded dark brownish-green pigments across their body to copy the motion of swaying seaweed. While these shapeshifting skills certainly come in handy for inconspicuous disguises, there are many other reasons octopuses and other cephalopods change their skin — and they may surprise you.