Several years ago, in the subtropical waters of southern Japan, divers spotted large geometric shapes sculpted in the sandy seabed. The circles were roughly two metres (6ft) across and formed of two concentric rings with spokes radiating from the centre. They were an aquatic version of unexplained crop circles. No one could work out what, or who, had made these mysterious shapes.
Then, a team of scientists finally caught sight of the seabed artists in action. They saw a small, male pufferfish (from the Torquigener genus), around 12cm (4in) long, darting across the sand, shimmying his fins and creating patterns in the sand. After that, more sand-sculpting puffers were spotted drawing circles on the seabed, each one performing a similar series of steps.
First, a male traces basic circular shapes,…
