Don’t mess with the blue-ringed octopus – its neurotoxin can kill a human in minutes. But before it bites, releasing venomous saliva through its beak, the octopus sends out a warning—bright blue rings that suddenly iridesce all over its body. How? By flexing its muscles. The blue rings are always there, but pouches of skin conceal their iridescence when the octopus is relaxed.
(i got an excellent picture again 😉 )