With which arm does an octopus greet you?

If being left-handed in a right-handed world is confusing, spare a thought for the octopus.

Ruth Byrne and colleagues at the Konrad Lorenz Institute, Austria, found that the waters became rather murky when they carried out the first study of handedness in eight of the marine invertebrates.

It emerged that some individual octopuses had a consistent preference as to which sided arm they use - two were left-handed, one right-handed the other five were ambidextrous - and they could also be categorised as frontal-handed or hind-handed.

The study was presented this week at the annual meeting of the Animal Behavior Society in the US.