Nature
A fist-sized fish sculpts an underwater crop circle to find a mate
For over a decade, divers off Japan's Amami Oshima island found mysterious 2-meter geometric circles on the seafloor with no explanation. In 2012, biologists traced them to a single male pufferfish, Torquigener albomaculosus, who spends 7-9 days fanning his fins to carve radial ridges that funnel fresh, oxygen-rich water to a central nest where a female will lay her eggs.