LONDON (AFP) - British marine experts have found what they claim is a world first -- a six-legged octopus, or "hexapus," whom they have christened Henry.

The unique sea creature, which has two limbs fewer than a normal octopus, is believed to be the result of a birth defect rather than an accident, say his keepers at the Blackpool Sea Life Centre in northwest England.

Henry was discovered in a lobster pot off the north Wales coast two weeks ago, and was one of eight creatures that Sea Life staff picked up from a local marine zoo there -- where staff hadn't noticed his missing legs.

It was only when he attached himself to the inside of a glass tank that Sea Life staff noticed he was two limbs short of a full set. Octopuses are renowned for having three hearts and blue blood, but not usually six legs.