How do cephalopods change their skin texture to resemble sand, coral, or seaweed?

Cephalopods change their skin texture to mimic their surroundings by erecting branched or spikelike structures known as papillae. These physical alterations, often accompanied by the curling of their arms, allow the animals to effectively camouflage themselves by imitating the appearance of objects such as sand, coral, or seaweed.1

While these textural changes provide physical mimicry, they are frequently used in conjunction with the animal's ability to manipulate its skin color through chromatophores and reflecting cells to achieve a more complete disguise. These behavioral patterns are part of a sophisticated suite of responses—including alarm displays and defensive posturing—that are controlled by the cephalopod's complex nervous system.1