Elaborate circles of sand and pebbles have been spotted off the coast of a Japanese island.

Prior to 2011, these strange, mandala-like circles found under the shallow sea were a mystery, and the identity of their architects was anything but expected.

They are constructed for an annual mating ritual by male white-spotted pufferfish, reports Japanese news. The 15-centimeter-long fish use their little fins to excavate the series of trenches during the mating season.

It takes the animal around 3 weeks to complete the sand mandala spawning nest, after which they escort the females there.

After this, they change professions from builders to protectors, guarding the eggs for 5 days until they hatch.

"We hope a great number of divers will be able to see the nests while following observation rules," said Katsuki Oki, 52, head of the Amami Marine Life Research Association, who took excellent photographs of these nests on the Oshima Straight seabed off southwest Japan's Amami-Oshima Island.

For centuries, whether with cooking implements or cars, the Japanese have been famous for their craftsmanship. Evidently, this trait extends to other branches of the tree of life on the famous islands.

WATCH how these fish make their nests, but be sure to see Oki's video HERE...

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