Shown in figure 1, the blue-ringed octopus may be small—the size of a golf ball, typically—yet equipped with a highly potent neurotoxin it can be deadly. As their name suggests, the octopuses feature around 60 highly conspicuous blue rings and (in some species) lines along their bodies and arms. The blue rings and lines exhibit iridescence—that is, they change color with the angle of observation and angle of illumination—an optical phenomenon caused by the differential refraction and reflectance of light waves on the animal.
Cephalopods, who spend much of their time hidden, are well known for their instant camouflage. Yet within the blink of an eye, the animals can change their appearance to be stunningly bright and colorful. Blue-ringed octopuses are no exception. When threatened, they quickly expose their blue rings in a series of bright flashes. Those flashes are an example of aposematism, a warning intended to deter...
