The blue-ringed octopus: small, vibrant and exceptionally deadly

Blue-ringed octopuses are undeniably stunning. When they are alarmed, these animals will show off the eponymous iridescent blue rings that cover their body and arms.

But their adorably small size and Instagrammable appearance is deceptive: blue-ringed octopuses are some of the ocean’s most toxic animals.

What is a blue-ringed octopus and where do you find it?

Blue-ringed octopuses are a group of highly venomous cephalopods.

These little octopuses have been found in the Pacific and Indian oceans. They typically live on coral reefs and rocky areas of the seafloor, though some may be found in tide pools, seagrass and algal beds. They are usually nocturnal, emerging at night to hunt crustaceans and sometimes small fish.

As their name suggests, these octopuses feature numerous blue rings on their bodies and arms. These rings are an example of aposematism, where animals use bright colours as a warning to would-be predators.

But unlike other aposematic animals such as poison dart frogs or velvet ants, which permanently display their bright colours, blue-ringed octopuses only show theirs off when they feel threatened.

Octopuses have thousands chromatophores under their skin. These are specialised cells that allow them to change colour instantaneously. Blue-ringed octopuses put on a threat display using these cells and…