blue ringed octopus

Many animals and plants use color to warn predators to stay away, and the blue ringed octopus is no exception. When this small mollusk is disturbed, blue circular rings light up all over its body. This colorful display is the octopus's way of saying, "Stay back—I'm about to bite!" One of the deadliest animals in the sea, the blue ringed octopus has a venomous bite that can instantly paralyze and kill a human.

Image credits: main image, courtesy of Roy Caldwell.