When researchers discovered the pufferfish was the answer to a long-standing underwater puzzle, their documentation also showed the culprit to be very different from any of its known relatives.

Beautiful circular designs have been spotted on the Japanese sea bed since 1995, but until recently their origins remained a mystery.

Finally a pufferfish was observed building the sandy structures and last year the behaviour was shown to be a tactic for attracting mates

The study also provided clear underwater images of the pufferfish from which researchers spotted the possibility that the species was new to science.

Two specimens, a male and a female, of what has now been called white-spotted pufferfish (Torquigener albomaculosus) were collected from the seas off the Ryukyu Islands, Japan.

The colouration of the head and body, brown with white spots on their back, and silvery white with white spots on their abdomen, helped scientists distinguish the white-spotted pufferfish from all other species of the genus Torquigener.

It is fully described in the journal Ichthyological Research.

Divers have observed white-spotted pufferfish on the sandy sea bottom off the south coast of Amamioshima Island at depths between 10 - 27m.

The discovery brings the total number of species of Torquigener to 20.

The new species is thought to be the only pufferfish to create geometric circles ahead of mating, the process was filmed for the BBC series Life Story, first shown last month.