They might be tiny and docile, but the blue-ringed octopus (Hapalochlaena lunulata) is one of the most venomous animals in the world. While resting, this golf ball-sized cephalopod is a pale brownish yellow to blend into its surroundings. But when agitated, the blue-ringed octopus lives up to its name by flashing 50-60 iridescent blue rings in a third of a second as a warning signal. A new study published in the Journal of Experimental Biology reveals the octopuses have a unique way of producing these colorful flashes: by flexing their muscles.
Check out more here, along with an awesome close-up video of an octopus flashing its blue rings.