Octopus

The blue-blooded genius with three hearts

An octopus has 3 hearts, blue blood and 8 arms! Each arm has its own 'brain' — the arms think for themselves. In one second it changes its colour and skin texture to look like a rock. An octopus can open jars and escape mazes — it's the cleverest invertebrate in the sea.

The common octopus (Octopus vulgaris) is a cephalopod mollusc of warm waters in all oceans. Two-thirds of its 500 million neurons are in its arms — each arm tastes and moves on its own. Using chromatophores (pigment cells) and papillae it changes colour and texture in 0.3 seconds, even though it's colour-blind (its eyes can't see colour!). Its copper-based blood — haemocyanin — is blue. Two hearts pump blood to the gills, one to the body. Boneless, it squeezes through a coin-sized hole. It escapes by squirting ink. It lives only 1–2 years; the female guards her eggs without eating and dies. Lab studies prove it can open jars, solve mazes and recognise individual people.

Fun facts

• An octopus has 3 hearts and 9 'brains'.
• An octopus can squeeze through a coin-sized hole — it has no bones.
• An octopus can't see colours, yet it can turn any colour — scientists still don't know how.