Octopuses open jars, escape tanks and recognise individual people. For an animal more closely related to snails than to us, that is remarkable.

A distributed brain

A common octopus has around 500 million neurons — and roughly two-thirds of them are in its arms rather than its head. Each arm can explore, taste and grasp with a degree of independence.

Unusual bodies

  • Three hearts: two pump blood through the gills, one through the rest of the body.
  • Blue blood: a copper-based molecule, haemocyanin, carries oxygen.
  • Living camouflage: skin cells change colour and texture in a fraction of a second.

Clever behaviour

Octopuses have been observed using coconut shells as portable shelters and solving puzzles in laboratories. Their intelligence evolved independently of vertebrates — a striking example of convergent evolution.