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.

Scientific name: Hapalochlaena lunulata
Size: about 8 inches long
Diet: crabs and fish
Habitat: shallow coral reefs off the coasts of Papua New Guinea
Characteristics: yellowish-brown skin; glowing blue rings appear when provoked
Significance: helps keep populations of crabs, fish, and other marine organisms in balance

Image credits: main image: courtesy of Roy Caldwell.