Ask anyone how many arms an octopus has and the usual answer will be eight. But scientists now insist these nautical animals only have six. 

In a new study they found that the creatures used six of their tentacles as arms and two as legs.

Marine experts at 20 Sea Life centres across Europe gathered data from over 2,000 separate observations.

They found common octopuses moved over the ground using their back two limbs, leaving the remaining six for eating.

Scientists have found that octopuses use two tentacles for walking and four as arms

Claire Little, a marine expert from the Weymouth Sea Life Centre in Dorset, said: 'We've found that octopuses effectively have six arms and two legs.

'It had been thought they used four tentacles for movement and the other four for feeding and manipulating objects.

'But observations showed that they use the rearmost two to get around over rocks and the seabed.

'They also use these two legs to push off when they wish to swim, and then other tentacles are used to propel them.'

Four legs up, two legs down: An octopus goes for a walk

The results came out of a study designed to show if octopuses favoured one side or the other.

The study had involved giving them jam jars and Rubik's Cubes to play with in a bid to see  if the creatures favour a particular tentacle for handling objects.

While there is no obvious difference between any of the tentacles, experts were surprised to note how often the octopuses' third tentacle from the front was employed for eating.

They also concluded the creatures favour no side and are ambidextrous.