A giant Pacific octopus called Mavis has helped researchers to prove that the one thing everyone knows about the creatures is wrong.
The name octopus is derived from the ancient Greek for "eight feet." Mavis, who lives in a tank at Weymouth Sea Life Centre on England's south coast, actually has six "arms" and two "legs."
Researchers who were studying octopuses' behavior were taken aback to discover that some of the most basic assumptions about them were wrong.
Until now, it had been believed that the tentacles were deployed in two equal sets, one set of four for propulsion and the other for manipulation.
The research, conducted at 20 centers across Europe, was originally intended to establish whether octopuses favored one side over the other, as people do, or were multidextrous.
Toys including a Rubik's Cube were placed in the octopus tanks and a careful watch was made of which limbs the animal used to play with them.
Claire Little, who led the research at Weymouth, where the project was devised, said: "We've found that octopuses effectively have six arms and two legs."